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Nitrogen (N) is one of the most important elements for plant growth and development. To reveal the interspecific variations of poplar species in response to changes in N levels and the essential traits that are closely linked to nitrogen use efficiency (NUE), six poplar species were subjected to 0.25, 2.5 or 7.5 mM NH4NO3. The morphological and physiological traits were analyzed, and the effects of species and N nutrition on each trait were determined. The roots of Populus popularis (Pp) were more sensitive to low N, whereas, P. deltoids (Pd) had the highest root biomass irrespective of N levels. The root morphological traits (e.g., total root surface area, total root length, root volume, and fine root surface area) were more affected by the genotype than N levels, and were positively correlated with low N. Conversely, photosynthesis and biomass accumulation in aerial parts were positively correlated with high N and were more affected by soil N availabilities. Considerable morphological variations existed among the analyzed poplar species, and contributed more to the interspecific variations than the physiological traits in these poplar species. The highest NUE was found in Pp under low N, and the lowest one was detected in Pd under high N. In addition, Pearson correlation analysis revealed that most morphological and physiological traits were tightly correlated with NUE among these poplar species in response to changes in N levels. These results indicate that interspecific variations exist within these poplar species, and that NUE is more affected by the N nutrition status than genotype.

Root hairs form a substantial portion of the root surface area. Compared with their nutritional function, the physical function of root hairs has been poorly characterised. This study investigates the physical role of root hairs of Arabidopsis thaliana seedlings in interaction of the root with water and soil and in plant survival upon soil disruption. Five transgenic lines with different root hair lengths were used to assess the physical function of root hairs. Upon soil disruption by water falling from a height (mimicking rainfall), long-haired lines showed much higher anchorage rates than short-haired lines. The root-pulling test revealed that a greater amount of soil adhered to long-haired roots than to short-haired roots. When seedlings were pulled out and laid on the soil surface for 15 d, survival rates of long-haired seedlings were higher than those of short-haired seedlings. Moreover, the water holding capacity of roots was much greater among long-haired seedlings than short-haired seedlings. These results suggest that root hairs play a significant role in plant survival upon soil disruption which could be fatal for young seedlings growing on thin soil surface with a short primary root and root hairs as the only soil anchoring system.

Paratecoma peroba is a native Brazilian forest species of great economic and ecological interest, which is currently at risk of extinction owing to excessive wood exploration. The use of the mini-cutting technique could facilitate the vegetatively propagation of this species. The objective of the present study was to establish a vegetative propagation protocol for P. peroba using the mini-cutting technique. In the first experiment, were tested five concentrations of indolbutiric acid (IBA; 0, 1, 2, 4 and 8 g.L-1) and two types of substrates (sand and a commercial substrate based on ground Pinus bark, coconut powder, and mineral additives). In the second experiment, were tested three types of mini-cuttings (apical of 6 cm and 10 cm, and intermediary of 4 cm) and two leaf area sizes (total leaf area and reduced to 50% of leaf area). The results showed that P. peroba could be vegetatively propagated using the mini-cutting technique with up to 82.5% rooting. There was only 5.6% of mini-cutting rooted in sand. High concentrations of IBA promotes decrease in rooting and number of roots. The 10 cm apical mini-cuttiing tend to form clones with better quality standards. The maintenance of the leaf area promotes the attainment of roots with greater root surface area, volume and dry mass of P. Peroba plants.

A hydroponic system was considered to be an appropriate method for root investigations, particularly if the method can be established as a screening technique to classify differences in root traits among sugarcane lines. The aim of the research was to classify root and shoot characters of sugarcane lines grown under hydroponic conditions and to investigate their correlation with the field measurements. Hydroponic and field tests used a randomized complete block design (RCBD). Eight elite sugarcane lines were assigned as treatments. Shoot and root traits were measured at 3 months after transplanting in the hydroponic experiment, and field trial measured root length density (RLD) at 4 months after planting. Root and shoot traits under the hydroponic system showed significant differences among sugarcane lines. KK3 had a high root surface area, root volume, root length and root dry weight and TBy27-1385 demonstrated a high stem height and stem dry mass. Moreover, root dry weight, root volume and root surface area positively correlated with shoot dry mass. Positive correlation was exhibited between root traits such as dry weight of root and root length derived from hydroponic studies and RLD derived from field conditions.

Phosphorus (P) is an important macronutrient required for crop growth but a finite resource in agriculture. The objective of this study was to examine the effects of soybean seed size and seed P content on growth and P accumulation up to anthesis (30–40 DAP). Pot experiments were carried out in a greenhouse with 15 soybean genotypes of different seed size (TKW 146–304 g) and with two substrates differing in plant available P, i.e., low P (LP) at 6.17 mg kg−1 vs. high P (HP) at 68.12 mg kg−1 CAL-P. The observations included measurements of seed and shoot dry matter and P concentrations as well as root characteristics. In the case of LP, shoot P accumulation relied, to a large degree, on seed P reserves during the vegetative growth period. In the case of HP, however, the role of seed P is negligible with regard to absolute P uptake. Yet, a very close linear relationship between seed P and shoot P uptake was also confirmed at HP. Some genotypes reacted more positively than others on HP in biomass production and P uptake, but none of the selected genotypes showed an outstanding biomass production or P uptake under LP. Total root length or root surface area of soybean did not explain differences in P uptake between genotypes at either P supply level. Overall, no substantial genotypic differences were observed in P use efficiency under P deficiency apart from the effect of seed P reserves. We conclude that seed size can be considered an important trait when screening genotypes for fast early P accumulation and growth.

Plant root hairs are cylindrical tubular projections from root epidermal cells. They increase the root surface area, which is important for the acquisition of water and nutrients, microbe interactions, and plant anchorage. The root hair specification, the effect of root hairs on nutrient acquisition and the mechanisms of nutrients (calcium, iron, magnesium, nitrogen, phosphorus, and potassium) that affect root hair development and growth were reviewed. The gene regulatory network on root hair specification in the plant kingdom was highlighted. More work is needed to clone the genes of additional root hair mutants and elucidate their roles, as well as undertaking reverse genetics and mutant complementation studies to add to the current knowledge of the signaling networks, which are involved in root hair development and growth regulated by nutrients.

Grasses have a segmental morphology. Compared to leaf development, data on root development at the phytomer level are scarce. Leaf appearance interval was recorded over time to allow inference about the age of segmental sites that later form roots. Hydroponically grown Lolium perenne cv. Aberdart tillers were studied in both spring and autumn in increasing and decreasing day length conditions, respectively, and dissected to define the development status of roots of known age on successive phytomers basipetally on the tiller axis. Over a 90-day observation period spring and autumn tillers produced 10.4 and 18.1 root bearing phytomers (Pr), respectively. Four stages of root development were identified: (0) main axis elongation (~0–10 days), (1) primary branching (~10–18 days), (2) secondary branching (~18–25 days), and (3) tertiary and quaternary branching without further increase in root dry weight. The individual spring roots achieved significantly greater dry weight (35%) than autumn roots, and a mechanism for seasonal shift in substrate supply to roots is proposed. Our data define a root turnover pattern likely also occurring in field swards and provide insight for modelling the turnover of grass root systems for developing nutrient efficient or stress tolerant ryegrass swards.

Aims Poplars are ecologically and economically important tree genus, sensitive to ozone (O3). This study aimed to investigate modifying effects of elevated O3 on poplar root response to nutrient addition. Methods In pot experiment, young trees of an O3-sensitive Oxford poplar clone (Populus maximoviczii Henry x berolinensis Dippel) growing in soil with three levels of P (0, 40 and 80 kg ha-1) and two levels of N (0 and 80 kg ha-1) were exposed to three levels of O3 (ambient - AA, 1.5 x AA, 2.0 x AA) at a free air exposure facility. After one growing season, root biomass, fine root (

To assess the environmental risks of carbon capture and storage (CCS) due to underground CO2 leakage, many studies have examined the impact on plant growth, however, the effect of leaked CO2 on root morphology remains poorly understood. This study simulated the effects of CO2 leakage from CCS on maize (Zea mays L.) root systems through pot experiments&mdash, one control treatment (no added CO2) and two elevated soil CO2 treatments (1000 g m&minus, 2 d&minus, 1 and 2000 g m&minus, 1). Compared with the control, root length, root surface area, and root volume were reduced by 44.73%, 34.14%, and 19.16%, respectively, in response to CO2 treatments with a flux of 2000 g m&minus, 1. Meanwhile, the fine root length in CO2 treatments with a flux of 1000 g m&minus, 1 were reduced by 29.44% and 45.88%, respectively, whereas no obvious difference in regard to coarse roots was found. Understanding changes in plant root morphology in this experiment, especially the decrease in the fine root length, are essential for explaining plant responses to CO2 leakage from CCS.

Increasing manganese (Mn) deficiency in soils emphasizes strategies for breeding genotypes with increased Mn efficiency. The present investigation evaluated Mn efficiency of 11 rice genotypes w.r.t. basal, foliar, and basal+foliar Mn application in field and glasshouse conditions. The genotypes with B + F application had higher leaf area (LA), SPAD index, root length (RL), root surface area (RSA) and mean half distance between roots (MHDR), and ultimately higher Mn efficiency under both growing conditions. The results of correlation analysis depicted strong positive relation between grain yield and LA (0.60) and SPAD index (0.53). The root characteristics viz., RL, RSA, and MHDR could, respectively, explain 76%, 77%, and 83% of variation in grain yield emphasizing the importance of superior root geometry in regulating mechanism pertaining to differential Mn efficiency. The breeders could select the traits for better root geometry along with high yield in breeding programs to develop Mn efficient g...

Root foraging and root physiology such as exudation of carboxylates into the rhizosphere are important strategies for plant phosphorus (P) acquisition. We used 100 chickpea (Cicer arietinum) genotypes with diverse genetic backgrounds to study the relative roles of root morphology and physiology in P acquisition. Plants were grown in pots in a low-P sterilized river sand supplied with 10 mu g P g(-1) soil as FePO4, a poorly soluble form of P. There was a large genotypic variation in root morphology (total root length, root surface area, mean root diameter, specific root length and root hair length), and root physiology (rhizosheath pH, carboxylates and acid phosphatase activity). Shoot P content was correlated with total root length, root surface area and total carboxylates per plant, particularly malonate. A positive correlation was found between mature leaf manganese (Mn) concentration and carboxylate amount in rhizosheath relative to root DW. This is the first study to demonstrate that the mature leaf Mn concentration can be used as an easily measurable proxy for the assessment of belowground carboxylate-releasing processes in a range of chickpea genotypes grown under low-P, and therefore offers an important breeding trait, with potential application in other crops.

Roots are the most important plant organ for absorbing essential elements, such as water and nutrients for living. To develop new climate-resilient soybean cultivars, it is essential to know the variation in root morphological traits (RMT) among diverse soybean for selecting superior root attribute genotypes. However, information on root morphological characteristics is poorly understood due to difficulty in root data collection and visualization. Thus, to overcome this problem in root research, we used a 2-dimensional (2D) root image in identifying RMT among diverse soybeans in this research. We assessed RMT in the vegetative growth stage (V2) of 372 soybean cultivars propagated in polyvinyl chloride pipes. The phenotypic investigation revealed significant variability among the 372 soybean cultivars for RMT. In particular, RMT such as the average diameter (AD), surface area (SA), link average length (LAL), and link average diameter (LAD) showed significant variability. On the contrary RMT, as with total length (TL) and link average branching angle (LABA), did not show differences. Furthermore, in the distribution analysis, normal distribution was observed for all RMT; at the same time, difference was observed in the distribution curve depending on individual RMT. Thus, based on overall RMT analysis values, the top 5% and bottom 5% ranked genotypes were selected. Furthermore, genotypes that showed most consistent for overall RMT have ranked accordingly. This ultimately helps to identify four genotypes (IT 16538, IT 199127, IT 165432, IT 165282) ranked in the highest 5%, whereas nine genotypes (IT 23305, IT 208266, IT 165208, IT 156289, IT 165405, IT 165019, IT 165839, IT 203565, IT 181034) ranked in the lowest 5% for RMT. Moreover, principal component analysis clustered cultivar 2, cultivar 160, and cultivar 274 into one group with high RMT values, and cultivar 335, cultivar 40, and cultivar 249 with low RMT values. The RMT correlation results revealed significantly positive TL and AD correlations with SA (r = 0.96) and LAD (r = 0.85), respectively. However, negative correlations (r = −0.43) were observed between TL and AD. Similarly, AD showed a negative correlation (r = −0.22) with SA. Thus, this result suggests that TL is a more vital factor than AD for determining SA compositions.

Temporal and spatial variations in ozone levels and temporal changes in solar radiation greatly influence ultraviolet radiation incidence to crops throughout their growth, yet the interactive effects of CO2 and UV-B radiation on Basil production under sunlight environmental conditions has not been studied. Basil ‘Genovese’ plants grown under sunlit plant growth chambers were subjected to a combination of supplemental UV-B (0 and 10 kJ m−2d−1) and ambient (420 ppm) and elevated (720 ppm) CO2 treatments for 38 days after 14 days of germination. UV-B radiation treatments caused a decrease in basil stem branching, fresh mass, and stem dry mass under both CO2 treatments when harvested after 17 and 38 days of treatment. There was also an increase in basil leaf surface wax under UV-B (10 kJ m−2d−1) treatment compared to controls (0 kJ m−2d−1). Elevated CO2 treatments caused a decrease in morphological features, including specific leaf area and fresh mass. Interactive effects between UV-B and CO2 treatments existed for some morphological features, including plant height, root surface area, and average root diameter. Understanding the impacts that CO2 and UV-B radiation treatments have on basilcan improve existing varieties for increased tolerance while simultaneously improving yield, plant morphology, and physiology.

Crops that acquire phosphorus more efficiently could reduce some of the environmental problems of fertilizers. We conducted two experiments to evaluate seven spring oilseed rape cultivars for their relative efficiency to use or acquire P under conditions of deficiency (4.6 mg Olsen P kg−1) and P application (80 mg P kg−1). Based on biomass, P content, P acquisition and use efficiency, cultivars were categorized as efficient responsive, non-efficient responsive, efficient non-responsive and non-efficient non-responsive. We also measured and compared root diameter, root surface area and total root length in two selected cultivars, and found that the Dalgan cultivar, which was efficient in P acquisition, was also an efficient accumulator of biomass under the P deficiency, and that P acquisition was related to higher Ca uptake. The responsible mechanism for P efficiency was suggested to be higher P uptake, which prompts the formation of larger root systems and improves plant access to soil P.

As terrestrial plants are rooted in one place, their metabolism must be acclimatized to continuously changing environmental conditions. This process is influenced by different metabolic traits of plant organs during ontogeny. However, direct measurement of organ-specific metabolic rates is particularly scarce, and little is known about their roles in whole-plant metabolism. In this study, we investigated size scaling of respiration rate, fresh mass and surface area of leaves, stems and roots in 65 seedlings of Fagus crenata Blume (2 weeks to 16 months old). With the increase in plant mass, the proportion of roots in whole plants increased from 20.8 to 87.3% in fresh mass and from 12.8 to 95.0% in surface area, whereas there was only a 15.6 to 60.2% increase in respiration rate. As a result, the fresh-mass-specific and surface-area-specific respiration rates in the roots decreased by 85% and 90%, respectively, and these decreases were significantly size dependent. However, such a size-dependent decrease was not observed for the surface-area-specific respiration rate in the leaves and stems. It is likely that this rapid root development is specific to the early growth stage after germination and would help plants acquire water and nutrients efficiently (i.e., at relatively low respiratory carbon costs). Overall, it is probable that the establishment of F. crenata forests and survival of F. crenata seedlings could be promoted by substantial root growth, with a reduction in respiratory carbon cost. Published

Adenophora triphylla var. japonica Hara is a highly valued medicinal plant that is used to treat or prevent bronchitis, cough, cancer, and obesity. However, there has been no study on the production of Adenophora triphylla var. japonica Hara seedlings in a closed-type plant production system (CPPS). This study was conducted to examine the growth characteristics of Adenophora triphylla var. japonica Hara seedlings as affected by different growing media. The seeds were sown on a 128-cell plug tray filled with urethane sponges (US), LC grow foam (LC), rockwool (RW), or terra-plugs (TP). The seedlings were cultured for a duration of 54 days under temperature 25 &plusmn, 1&deg, C, a photoperiod of 12/12 h (light/dark), and light intensity of 180 &micro, mol&middot, m&minus, 2&middot, s&minus, 1 photosynthetic photon flux density provided by RB LEDs (red:blue = 8:2) in a closed-type plant production system (CPPS). The germination rate of Adenophora triphylla var. japonica Hara was significantly highest in the TP. Also, seedling shoot growth indicators of plant height, leaf length, leaf width, number of leaves, fresh weight (FW), and dry weight (DW) of the shoot, and leaf area were markedly the greatest in the TP and the lowest in the US. The SPAD (soil-plant analysis development) value was higher in the TP and US than in the LC or RW. In addition, the seedling root growth characteristics of total root length, root surface area, root volume, and number of root tips were significantly greatest in the TP. Moreover, the maximum root diameter, FW and DW of roots were the greatest in the TP. In conclusion, the results suggest that TP are viable for the growth development of Adenophora triphylla var. japonica Hara seedlings.

This study reports the application of a novel bioprospecting procedure designed to screen plant growth-promoting rhizobacteria (PGPR) capable of rapidly colonizing the rhizosphere and mitigating drought stress in multiple hosts. Two PGPR strains were isolated by this bioprospecting screening assay and identified as Bacillus sp. (12D6) and Enterobacter sp. (16i). When inoculated into the rhizospheres of wheat (Triticum aestivum) and maize (Zea mays) seedlings, these PGPR resulted in delays in the onset of plant drought symptoms. The plant phenotype responding to drought stress was associated with alterations in root system architecture. In wheat, both PGPR isolates significantly increased root branching, and Bacillus sp. (12D6), in particular, increased root length, when compared to the control. In maize, both PGPR isolates significantly increased root length, root surface area and number of tips when compared to the control. Enterobacter sp. (16i) exhibited greater effects in root length, diameter and branching when compared to Bacillus sp. (12D6) or the control. In vitro phytohormone profiling of PGPR pellets and filtrates using LC/MS demonstrated that both PGPR strains produced and excreted indole-3-acetic acid (IAA) and salicylic acid (SA) when compared to other phytohormones. The positive effects of PGPR inoculation occurred concurrently with the onset of water deficit, demonstrating the potential of the PGPR identified from this bioprospecting pipeline for use in crop production systems under drought stress.

Background Allelopathic rice releases allelochemicals through its root systems, thereby exerting a negative effect on paddy weeds. This research aimed to evaluate the relationship between fine-root traits and the rice allelopathic potential at the seedling stage. Methods Two allelopathic rice cultivars, ‘PI312777’ and ‘Taichung Native1,’ and one non-allelopathic rice cultivar, ‘Lemont,’ were grown to the 3–6 leaf stage in a hydroponic system. Their fine roots were collected for morphological trait (root length, root surface area, root volume, and root tips number) in smaller diameter cutoffs and proliferative trait (root biomass) analysis. Their root-exudates were used for quantitative analysis of phenolic acids contents and an evaluation of allelopathic potential. Correlation analysis was also used to assess whether any linear relationships existed. Results Our results showed that allelopathic rice cultivars had significantly higher fine-root length having diameters 0.2 mm. Discussion Our results implied that fine-root traits appears to be important in understanding rice allelopathy at the seedling stage. The high allelopathic potential of rice cultivars might be attributed to their higher length of fine roots

The growth characteristics of Paeonia ostii ``Fengdan`` seedlings roots in response to trichokonins-spray treatment were investigated in this study. One-year-old seedlings of P. ostii ``Fengdan`` were potted in plastic cups containing garden mold and grown under field conditions. The results showed that application of trichokonins significantly promoted root growth in P. ostii ``Fengdan`` seedlings. The total root projection area, total root surface area, total root volume, total root length, root number and root diameter of seedlings treated with 0.25 mg/L trichokonins were higher by 141.70, 116.59, 119.44, 55.97, 348.88 and 127.78%, respectively, than that of the control. Thus, the results supported the hypothesis that good growth condition for roots could directly improve their nutrient absorption and utilization efficiency, promoting plant growth and development.

A pot experiment was performed to investigate the variations in cadmium (Cd) accumulation among pak choi cultivars and its relationships to root morphology. The biomass, Cd accumulation and root morphology of 20 pak choi cultivars were determined in low and high Cd treatments. Significant variations in Cd accumulation and root morphological parameters were observed between pak choi cultivars. Cd concentrations in shoots differed between cultivars by a factor of 2.3 (13.3-30.8 μg g(-1)) and 2.6 (35.5-94.0 μg g(-1)) for low and high Cd treatments, respectively. The total Cd in plants positively correlated to the root length, root surface area, root volume, and root length/shoot biomass ratio in both Cd treatments. The shoot Cd concentration was also positively correlated with the root length, root surface area, and root length/shoot biomass ratio. Moreover, the proportion of fine roots (diameter less than 0.2 mm) was positively correlated with the total Cd in plants in low Cd treatment, and positively correlated with percentage of Cd in shoots in high Cd treatment. These results suggested that root morphology might be partially responsible for variation of Cd accumulation among pak choi cultivars. High Cd cultivars exhibit longer root length, greater root surface area, higher root volume, and a higher proportion of fine roots than low Cd cultivars.

Exogenous salicylic acid (SA) can alleviate salt stress in plants. Previous researches have been focused on SA’s role in leaf morphological and physiological characteristics, however, little information is available on its role in both leaf photosynthesis and root system architecture (RSA). A hydroponic study was conducted to analyze biomass, leaf photosynthesis, RSA parameters and expression of RSA genes in cucumber seedlings grown under four treatments, including control (CK), 50 mM NaCl (NaCl), 0.3 mM SA (SA) and 50 mM NaCl plus 0.3 mM SA (NaCl + SA). The results showed that compared with CK, both NaCl and SA treatments severely reduced relative growth rate (RGR) and leaf photosynthetic parameters (Fv/Fm, ΦII and Pn). However, compared with NaCl treatment, NaCl + SA treatment significantly increased RGR, leaf photosynthetic (Fv/Fm, ΦII and Pn) and RSA (total root length, root surface area, number and total length of primary and secondary LR) parameters. In addition, compared with CK, although both NaCl and SA treatments down-regulated expression of GL2 gene and up-regulated expression of RHD2 gene, NaCl + SA treatment notably up-regulated expression of NAC1, NAC2, GL2, EXP and down-regulated expression of RHD2. It is concluded that exogenous SA alleviated salt stress via effectively promoting leaf photosynthesis and RSA in cucumber seedlings. SA-mediated increment in expression of RSA genes, total length and number of primary and secondary LR could contribute to the improved RSA.

Fourteen Brassica species consisting of seven leafy vegetables and seven root vegetables were examined for (137)Cs uptake differences in relation to their fine-root morphological characters. A pot experiment was conducted from November 2014 to February 2015 in a Phytroton using a contaminated soil of Fukushima prefecture. Leafy vegetables showed bigger root diameters, larger root surface area and larger root volume. Consequently, leafy vegetables had higher (137)Cs uptake compared to root vegetables. Among the three fine-root parameters, only root surface area was observed as a significant contributing factor to higher (137)Cs uptake in terms of transfer factor (TF, dry weight basis). Kakina exhibited higher (137)Cs TF value (0.20) followed by Chinese cabbage (0.18) and mizuna (0.17). Lower TF values were observed in turnip (0.059), rutabaga (Kitanoshou) (0.062) and radish (Ha daikon) (0.064).

Resumo: O objetivo deste trabalho foi avaliar a distribuição do sistema radicular do cafeeiro conilon (Coffea canephora) irrigado e não irrigado. Utilizaram-se plantas de conilon da variedade clonal Emcapa 8111, genótipo 02, com cinco anos de idade. Utilizou-se o delineamento inteiramente casualizado, em parcela subsubdividida, com cinco repetições. Os tratamentos consistiram de: presença e ausência de irrigação (parcelas), 13 distâncias do tronco (dez no sentido da entrelinha e três no sentido da linha de plantio) e seis camadas de solo (0-60 cm) nas subparcelas. As raízes foram coletadas, lavadas, digitalizadas e processadas pelo programa Safira, para quantificar área superficial, comprimento, volume e diâmetro. As plantas de conilon não irrigadas apresentaram maiores área superficial, comprimento e volume de raízes por volume de solo, bem como distribuição de raízes menos discrepante na superfície do solo e em profundidade, em comparação às plantas irrigadas. O sistema de irrigação por gotejamento promove maior distribuição de raízes nas plantas irrigadas, na zona compreendida pelo bulbo úmido da irrigação. Abstract: The objective of this work was to evaluate the distribution of the root system of irrigated and nonirrigated conilon coffee (Coffea canephora). Conilon plants of the clonal variety Emcapa 8111, genotype 02, with five years of age, were used. The design was completely randomized in split-split plots with five replicates. The treatments consisted of: presence and absence of irrigation (plots), 13 distances from the stem (ten in the direction between rows and three of the planting row) and six soil layers (0-60 cm) in the split-plots. Roots were collected, washed, scanned, and processed by the Safira software to quantify surface area, length, volume, and diameter. Nonirrigated conilon plants showed greater root surface area, length, and volume per soil volume, as well as less discrepant distribution of roots in the soil surface and in depth, in comparison to irrigated plants. The drip irrigation system promotes higher root distribution in irrigated plants, in the area covered by the wet-bulb irrigation.

This study was performed to identify the effect of mixed bed soil on growth of aerial parts and root zone of daughter plants for nursery field strawberry seedling raising with expanded chaff. The plant height and leaf area of daughter plants were highest or largest in the mixed soil of ERH +RH (100:0, v/v), followed by ERH+RH (75:25). The higher the mixing ratio of RH, the shorter the plant height or the smaller the leaf area. A similar tendency was observed in fresh weight. Within a root diameter of 0-0.4 mm and a root height range of 0.4-0.8 mm, root surface area and volume were statistically significantly better with treatment of ERH+RH (100:0, v/v) compared to those of roots treated with ERH+RH (75:25), ERH+RH (50:50) and ERH+RH (25:75). The growth rate of aerial parts and root zone of daughter plants were noticeably lower in two mixing ratios of 50:50 and 25:75. According to the mixing ratios of ERH+CD surface treatment, the number of roots was greatest in plants treated with ERH+CD (80:20, v/v) and ERH+CD (85:15) on August 1. However, the number of roots was highest in plants treated with ERH+CD (85:15, v/v) on August 15. Root length was longest in the plant with no treatment, and drastically shortened from ERH+CD (90:10, v/v) in both surface and mixed treatment. Although root weight showed a significant difference in ERH+CD (90:10, v/v) treatment, its increase was gradual. The rate of root growth was highest in ERH+CD (85:15). These study findings suggest that the content ratios of mixed soil ERH+RH (75:25, v/v) or below and ERH+CD (85:15) are thought to be desirable for the production of high quality seedlings.

Made available in DSpace on 2015-11-03T15:29:56Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-12-17 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Information regarding the characteristics that affect P-uptake capacity may assist in the selection of more adapted potato (Solanum tuberosum L.) cultivars and more adequate fertilization management for each cultivar. This study evaluated the P-uptake capacity of potato cultivars (Agata, Asterix, Atlantic, Markies, and Mondial) grown under P-deficient (2 mg L-1) or P-sufficient (31 mg L-1) conditions in nutrient solution and related it to physiological parameters of uptake and morphological root characteristics. When the plants were 24 days old, they were subjected to a P-uptake kinetics study. The length and surface area of roots and the uptake kinetic parameters (I-max, K-m, and C-min) varied among potato cultivars. Phosphorus-deficient potato plants had an approximately 60% smaller root surface area and an increase of 86% in the I-max and net P influx compared with the plants in P-sufficient conditions. However, these modifications in P uptake kinetics can do not influence P acquisition in the soil environment due to very limited P diffusion. The amount of P accumulated by plants grown under P-deficient conditions was directly related to the root length and surface area; a greater root surface, as demonstrated by the Asterix cultivar, is the most important factor for achieving a greater P-uptake capacity. Under P-sufficient conditions, potato cultivars such as Markies and Mondial showed a balance between morphological root characteristics (medium/large length and surface area) and physiological parameters (medium/high I-max values and net P influx) and had a greater P-uptake capacity. However, under field conditions, the responses to P deficiency may be different due to the very limited diffusion of P in the soil and because plants can use additional mechanisms to improve their P uptake from the soil. (C) 2014 Elsevier B.V. All rights reserved. Sao Paulo State Univ UNESP, Ctr Res Trop Tubers &Starches CERAT, BR-18610307 Sao Paulo, Brazil Sao Paulo State Univ UNESP, Coll Agr Sci, Dept Crop Sci, BR-18610307 Sao Paulo, Brazil Sao Paulo State Univ UNESP, Ctr Res Trop Tubers &Starches CERAT, BR-18610307 Sao Paulo, Brazil Sao Paulo State Univ UNESP, Coll Agr Sci, Dept Crop Sci, BR-18610307 Sao Paulo, Brazil FAPESP: 2010/04987-6 FAPESP: 2010/18600-6

Two Rumex japonicus populations, one from copper (Cu) mine and the other from uncontaminated site, were studied for root morphology and biomass under Cu stress. Main root length and number of tips of the two populations were both significantly inhibited by Cu treatments. However, those of metallicolous population (MP) were higher than non-metallicolous population (NMP) under Cu stress. Cu treatments significantly inhibited root surface area in NMP while MP showed little difference from control. Cu treatments inhibited average root diameter and root/shoot ratio in NMP, but those in MP were significantly higher than control. Cu treatments significantly inhibited shoot biomass and root biomass in NMP. These results suggested that more assimilates allocated to root and the average root diameter increased under Cu stress to form a greater and stronger root might be partly reasons why R. japonicus can colonize the Cu enriched soils.

Green leaves face two fundamental challenges (i.e., carbon fixation and stress tolerance) during their lifespan. However, the relationships between leaf production potential and leaf tolerance potential have not been explicitly tested with a broad range of plant species in the same environment. To do so, we conducted a field investigation based on 107 woody plants grown in a common garden and complementary laboratory measurements. The values, as measured by a chlorophyll meter, were significantly related to the direct measurements of chlorophyll content on a leaf area basis. Area-based chlorophyll content was positively correlated with root surface area, whole-plant biomass, leaf mass per area (LMA) and force to punch. Additionally, LMA had a positive correlation with force to punch. Shrubs had a higher leaf chlorophyll content than trees; however, shrubs and trees exhibited a similar leaf lifespan, force to punch and LMA. These findings suggest that the production potential of leaves and their tolerance to stresses may be convergent in woody species and that the leaf production potential may differ between shrubs and trees. This study highlights the possibility that functional convergence and divergence might be linked to long-term selection pressures and genetic constraints.

Drought-induced tree susceptibility is a major risk associated with climate change. Here we report how an 11-week drought affected tracheid structure, gene expression, and above- and belowground growth in 5-year-old Norway spruce trees (Picea abies) under controlled conditions. The canopy of trees subjected to severe drought had significantly less current-year needle biomass, and fewer tracheids and tracheid rows in current-year shoots compared to fully watered control trees. Belowground tissues were more strongly affected by drought than aboveground tissues. In fine roots (

To relate the characteristics of root architecture and the kinetic parameters of nitrate (NO3) uptake, two typical lettuce cultivars (Lactuca sativa L.), ‘Sx1’ and ‘Nrnct’, were exposed to different nutrient solutions: 100% NO3-N (T1), 10% ammonium (NH4)-N + 90% NO3-N (T2), 10% NH4-N + 100% NO3-N (T3). The results obtained indicate that total root surface area, root volume, total root length and root number increased with the increased of NH4-N; the NH4-N in the nutrient solution had significant effects on the rates of NO− 3 uptake, Vmax of NO− 3 uptake kinetics in T1 was significantly higher than with T2 and T3, Km of NO− 3 uptake kinetics in T1 was lower than that of T2 and T3, but the difference was not significant, NH4-N inhibited NO− 3 uptake mainly due to the higher Vmax. Based on the NO− 3 uptake rate, NO− 3 content, Vmax and Km, the different cultivars differed in their nitrate uptake characteristics.

Uptake of potassium (K) in crops depends mainly on the root system. Field, pot and hydroponic experiments were carried out to characterise root morphological traits and examine their roles in K uptake and utilisation of vegetable soybean (edamame) (Glycine max (L.) Merr.). Of 40 genotypes, two high K-efficiency (HKE) and two low K-efficiency (LKE) genotypes were identified and compared at two levels of K application: nil or 120 kg K2SO4 ha–1. HKE genotypes had shorter total root length and smaller root surface area and root volume than LKE genotypes, but responded earlier to low-K conditions by adjusting root architecture. In plants receiving nil K, total root length was increased by 10.4–21.8% for HKE genotypes but decreased by 5.5–9.5% for LKE genotypes at the V4 stage relative to plants receiving applied K. HKE genotypes were more efficient in redistributing K from source to sink tissue, especially from leaf. Of the total K in vegetative tissues, 35.0–46.4% was redistributed to seed in HKE genotypes, whereas only 19.7–28.2% was redistributed in LKE genotypes. HKE genotypes also had a higher specific K uptake rate (K uptake per unit root length), 1.6–1.7 times higher than LKE genotypes at the R5 stage. This indirectly indicated a stronger root K acquisition in HKE genotypes. This study suggests that future vegetable soybean improvement with greater K efficiency should be focused on the selection of higher K-redistribution rate and specific K-uptake rate.

Low availability of phosphorus (P) is a major constraint to production of cotton (Gossypium hirsutum L.). The extent to which genotypic variation in root traits exists or contributes to P-acquisition efficiency (PAE) in cotton is unknown. To assess genetic variation in PAE, the biomass and P-acquisition characteristics of 32 cotton genotypes were evaluated in a hydroponic experiment. Significant genotypic variation in biomass and P content was detected among the cotton genotypes in two seasons. We then conducted a 2-year pot experiment to compare P-efficiency traits between three P-efficient and two P-inefficient genotypes under P-deficient and P-sufficient conditions (0 and 75 mg P2O5 kg–1 soil, respectively). We detected significant differences in biomass accumulation and allocation, P accumulation and allocation, root traits and PAE among the five cotton genotypes under P-sufficient and P-deficient conditions. Compared with P-inefficient genotypes, P-efficient genotypes had longer surface fine roots, and greater total root surface area, total root length, surface root length, and P concentration (partitioning index) in bolls. Root morphology, especially surface fine root length and middle root length, played an important role in P uptake under P-deficient conditions.

To determine an appropriate indicator and a suitable stage for evaluating tolerance of soybeans to aluminum (Al) toxin is one of the keys to effective breeding for the trait. Seventeen accessions selected as tolerant from a previous test program by using average membership index (FAi) as indicator, plus one tolerant (PI.416937) and one sensitive (NN1138-2) check, were assayed in sand culture pot experiments, totaling four experiments, each for evaluation at V3, V5, V7 and V9 stage, respectively, each in a randomized complete block design with three replications, and each genotype exposed to two Al levels (0 and 480 μM). The relative values of shoot dry weight (RSDW), root dry weight (RRDW), total plant dry weight (RTDW), total root length (RTRL) and total root surface area (RRSA) as the tolerance indicators as well as FAi were compared. All the indicators showed significant variation in Al tolerance among genotypes over and across the leaf stages, but Genotype × Stage interactions were significant only for RTRL and RRSA, indicating that they were less stable among stages than RTDW, RSDW and RRDW. Among the latter three, RTDW was chosen as the major indicator of Al tolerance due to its relatively better stability, higher correlation with other indicators and easier measuring procedure than the others. The seedling age applicable for screening was not definitive, but V5 appeared to compromise between time spent resulting from screening the relatively older seedlings at later stages and low variation among genotypes at a younger stage. The differences of Al tolerance among the tested accessions were further detected by using RTDW, and superior Al tolerant accessions identified were PI.509080 (South Korea), N23533 and N24282 (Northeast China) and PI.159322 (USA), comparable to the putative tolerant check PI.416937 (Japan) at all vegetative stages.

In the field, plants show better root growth in drying soil than in wet soil. However, the root growth enhancement has not been demonstrated clearly in the laboratory. In this study, the root growth response of wheat seedlings to moderate soil water deficits was characterized quantitatively in an environment-controlled chamber. Germinated seeds of wheat were grown for 15 days in the soil with a water potential ranging from field capacity (FC) to approximately –0.08 MPa. Theleaf area decreased with reduction in soil water potential. By contrast, the root surface area increased upon reduction ofthe soil water potential to –0.04 MPa while it decreased significantly in soil with a water potential of –0.08 MPa. The increase in surface area was obvious in the roots with a diameter of 0.2 to 0.4 mm and larger than 0.7 mm. Root weight increased with the reduction of soil water potential to –0.04 MPa. While specific root length decreased significantly with the reduction of water potential to –0.06 MPa, the specific root surface area did not. Assimilatestransported from shoot might be used in roots to increae the surface area mainly by increasing the diameter rather than the length in response to a moderate soil water deficit in wheat seedlings. This might result from the drought tolerance mechanism of osmotic adjustment in roots.

We examined the permeability of roots of Dutch ‘Dundee’ and Japanese ‘Reiyo’ varieties of tomato seedlings to nutrient solutions and potassium ions. Seedlings were grown under 5 different conditions: (1) Seedlings were grown in Otsuka-A nutrient solution adjusted to an electric conductivity (EC) of 2.4 dS·m−1, and on the experiment day their roots were permeated with EC 2.4; (2) before the experiment day the EC was changed to 7.2 dS·m−1, and then roots were permeated with EC 7.2 in the experiment; (3) roots were permeated with potassium chloride (KCl) solution whose water potential was equivalent to EC 2.4 in the experiment; (4) before the experiment day the EC was changed to EC 7.2, and then roots were permeated with KCl solution whose water potential was equivalent to EC 7.2 in the experiment; and (5) roots were permeated with that KCl solution whose water potential was equivalent to EC 7.2 in the experiment. We measured the root permeability of seedlings grown in each solution, and the water potentials of exudates by using a pressure chamber and an isopiestic psychrometer. The nutrient solution or potassium solution in the chamber was forced into the plants under pressure. We then measured the quantity of extraction from the cutting surface of the root and root surface area to calculate root permeability. As a result, we found that, except in the KCl permeability experiment with a water potential equivalent to EC 2.4, the Japanese variety had greater permeability of nutrient solution and potassium. On this basis we conjectured that the Japanese variety ‘Reiyo’, whose root permeability was high, is able to assimilate more water and nutrients than the Dutch variety ‘Dundee’. On this basis we found that differences in root permeability can be considered one reason why ‘Reiyo’ grows larger than ‘Dundee’ in the initial part of its growth period.

To understand the physiological mechanism that confers Cd sensitivity, root morphology and Cd uptake kinetics of the Cd-sensitive mutant and wild type rice were investigated. The root length, root surface area, and root number of mutant rice decreased more significantly with increasing Cd concentration in growth media compared with the wild type rice. The uptake kinetics for 109Cd2+ in roots of both the mutant and wild type rice were characterized by a rapid linear phase during the first 6 h and a slower linear phase during the subsequent period. Concentration-dependent Cd2+ influx in both species could be characterized by the Michaelis-Menten equation, with similar apparent Km values for mutant and wild type rice (2.54 and 2.37 µM, respectively). However, the Vmax for Cd2+ influx in mutant root cells was nearly 2-fold higher than that for wild type rice, indicating that enhanced absorption into the root is one of the mechanisms involved in Cd sensitivity in mutant rice.

Trinexapac-ethyl (TE) [4-(cyclopropyl-α-hydroxy-methylene)-3,5-dioxocyclohexanecarboxylic acid ethyl ester] and paclobutrazol (PAC) [(2RS,3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1H-1,2,4-tri-azol-1-yl)pentan-3-ol] are routinely used to suppress clipping production. Single-leaf turfgrass C exchange rates (CERs) in response to plant growth regulator (PGR) treatment have not been characterized. Individual Kentucky bluegrass (KBG, Poa pratensis L.) plants received label rates of TE or PAC and were placed in growth chambers at 23/18 or 30/25°C. Photosynthetic efficiency and CER measurements were recorded every 4 d for 44 d. Total root length (TRL), root surface area (SA), and average root diameter were measured at the end of the study. Reductions in CERs of TE- or PAC-treated plants were short lived with CERs suppressed 17 to 29% of control (POC) at 4 and 12 days after treatment (DAT), respectively. Plants treated at 23/18°C with PGRs typically had short-lived increases in CERs following CER suppression. A similar pattern of CER response to PGR treatment was observed at the 30/25°C temperature regime. Quantum efficiency was unaffected, but plants treated with PGRs had reduced root growth. PAC caused the greatest reduction in TRL and SA while increasing root diameter. A decline in TRL and SA in conjunction with increased tillering indicates that PGR reduced TRL and SA on a tiller basis. Changes in single-leaf CERs do not fully explain PGR-induced changes in plant growth.

Application of phosphorus (P) fertilizer is an important factor for improving the tolerance to water deficit in many plants. A pot experiment was conducted to identify the effects of P application on soybean adaptability to water deficit at the R1 (initial flowering) and R4 (full pod) stages through the investigation of root morphological traits, plant P uptake and resultant yield in two soybean (Glycine max L. Merrill) cultivars (Dongnong 46 and Heisheng 101). The four levels of P application were 0, 7.3, 14.6 and 29.2 mg kg−2, respectively. The three water treatments were (1) 65–75% of field water capacity (FWC) as a well-watered control, (2) 30–40% of FWC at the R1 stage, and (3) 30–40% of FWC at the R4 stage. Root traits, plant uptake of P and yield were significantly reduced by water deficiency at different growth stages, especially at the R4 stage. Application of P enabled to alleviate the adverse effects of water deficit, to increase the root dry weight, root length and root surface area, and to sl...

Elsholtzia argyi and Elsholtzia splendens, which are Chinese endemic Pb/Zn mined and Cu mined ecotype respectively, were investigated in the aspect of their response to Pb toxicity in the presence or absence of EDTA addition. After 8 d's Pb treatment, root length, root surface area and root volume of E. splendens decreased much more than those of E. argyi, and reduced considerably with increase of Pb, while no marked change was noted for root average diameter. Compared to E. argyi, length of root with diameter (D)0.2 mm was significantly reduced for E. splendens as Pb increasing. Root with cross-sectional area of D0.1 mm for E. splendens was at Pbor =10 mg/L, while for E. argyi, it was at Pbor =25 mg/L. DW of E. splendens decreased much more than that of E. argyi with increase of Pb. E. argyi exhibited much more tolerance to Pb toxicity than E. splendens. Treatment with 100 mg/L Pb plus 50 mmol/L EDTA significantly decreased the length and surface area of Dor =0.2 mm root, increased the length and surface area of 0.2or =Dor =0.8 mm root for the case of E. argyi, while for E. splendens, length and surface area of D0.6 mm root reduced, as compared to 100 mg/L Pb treatment, alone. At 100 mg/L Pb, shoot Pb accumulation in E. splendens and E. argyi were 27.9 and 89.0 microg/plant DW respectively, and much more Pb was uptaken by the root and translocated to the stem of E. argyi as compared to E. splendens. Treatment of the plant with 100 mg/L Pb plus 50 mmol/L EDTA increase leaf Pb accumulation from 16.8 to 84.9 g/plant for E.splendens and from 18.8 to 52.5 g/plant for E. argyi, while both root and stem Pb pronouncedly reduced for both Elsholtzia species. The increased translocation of Pb to the leaf of E. splendens than that of E. argyi at the treatment of 100 mg/L Pb plus 50 mmol/L EDTA should be further investigated.

Biostimulants are used to reduce the stress associated with non-dormant (summer dug) harvest of field-grown nursery stock; however, the effectiveness of biostimulant treatment is uncertain. This study tested the effects of three application methods of Bioplex™ (a commonly used biostimulant) to container-grown red oak seedlings on whole plant transpirational water use and growth before and after root pruning. Root pruning was used to simulate field harvest; it removed 59% of the seedling's total root surface area. Bioplex™ application by foliar spray, soil drench or a combination of foliar spray and soil drench, significantly reduced whole plant transpirational water use by 15% for three days after application, relative to untreated control seedlings. Root pruning significantly reduced whole plant transpiration, compared to non-root-pruned seedlings, and had a greater effect on transpiration than any Bioplex™ treatment. The previous season's Bioplex treatment had no effect on the spring growth flush following fall root pruning. Root pruning in fall significantly reduced root and total plant dry weights the following spring. Although Bioplex™ applications significantly reduced transpiration for three days after application, there does not seem to be any long-term beneficial effect when used to mediate summer digging transplant stress.

The function and activity of a root system is closely linked to its normal environment, the soil. The soil volume exploited by the two species was calculated and a comparison showed that Calamus rotang exploited more soil volume than C. thwaitesii. The effective soil volume was also found to show an increase in C. rotang when compared to C. thwaitesii. Knowing the effective soil volume, the size of the polybag to be used in the nursery can be adjusted. The root spread of the two species shows that a 30 × 30 × 30 cm pit size will be sufficient for seedlings up to 2 years old. Rooting density is found to be more in the upper 30 cm layer of soil in both species. Root density, total root intensity and fine root intensity are higher in C. thwaitesii when compared to C. rotang. Root surface area also is more in C. thwaitesii. Hence, this species will be more efficient in water and nutrient uptake in the seedling stage. Both species are good soil binders.

A pond experiment was conducted to examine the influence of convective flow on root morphology of Typha domingensis plants grown in either sand, clay or a 50:50 mixture of the two sediments. The sediment types had different mean redox potentials; +14.6, −253 and −160 mV, respectively. To prevent convective flow in treatment plants, the leaves were pierced above the water surface twice weekly throughout the experimental period. Plants responded to both leaf piercing and sediment type but in different ways. The mean root length of intact plants was 11.5–30.5% greater than in pierced plants whilst the mean root surface area of intact plants was 39.8–54.8% greater than in pierced plants. In both cases, the greatest percentage difference was found in plants growing in sand. Other characteristics, including biomass and its allocation, responded to sediment type but not leaf piercing with plants growing more vigorously in clay. The morphology of the plants varied between the sediments. Based on the lacunal cross-sectional area, plants growing in clay had the greatest capacity for oxygen transport.

Two Triticum aestivum (Excalibur and Gatcher) and one Triticum turgidum conv. durum (Durati) genotypes (differing in the ability to grow and yield well in environments with low Zn availability) were grown in chelate-buffered, complete nutrient solutions providing either deficient or sufficient Zn supply and supplemented with sulphonylurea herbicide chlorsulfuron [2-chloro-N-(((4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino)-carbonyl)-benzenesulphonamide] at 0 or 4 mg m -3 . Compared to Zn-sufficient roots, plants grown under Zn deficiency had thicker roots on average, with a shorter length of the fine roots (diameters

Com o processo de degradação dos solos, extensas áreas da fronteira sudoeste do Rio Grande do Sul estão em processo de arenização. O uso de espécies florestais nativas pode ser uma alternativa para revegetação dessas áreas. O objetivo do trabalho foi avaliar o crescimento de mudas de Ipê amarelo e Leucena submetidas a doses de vermicomposto em solo sob processo de arenização da fronteira sudoeste do Rio Grande do Sul. O delineamento experimental foi inteiramente casualizado, utilizando-se duas espécies florestais, o Ipê amarelo (Tabebuia chrysotricha) e a Leucena (Leucaena leucocephala), três níveis de substrato, composto pela mistura de vermicomposto e solo arenoso (v:v) (0% vermicomposto: 100% solo; 25% vermicomposto: 75% solo; e 50% vermicomposto: 50% solo) com 9 repetições. A resposta à adição de vermicomposto foi diferente entre as duas espécies. A adição de 25% de vermicomposto ao solo arenoso proporcionou maior crescimento nas mudas de Ipê amarelo e Leucena. Contudo, plantas de Leucena apresentaram maior altura, comprimento e área superficial específica radicular que o Ipê amarelo em doses mais elevadas de vermicomposto adicionadas a solo arenoso.Palavra-chave: vermicompostagem, substrato orgânico, degradação do solo.VERMICOMPOST EFFECTON SEDLINGS OF Tabebuia chrysotricha AND Leucaena leucocephala IN SANDY SOIL ABSTRACTWith the soil degradation process, extensive areas of Rio Grande do Sul southwestern border are in sandification process. The native forest species use may be an alternative for revegetation of these areas. The aim of this study was to evaluate the growth of Tabebuia chrysotricha and Leucaena leucocephala seedlings under different vermicompost doses in soil under sandification process in Rio Grande do Sul southwestern border. The experimental design was completely randomized in a factorial (2 x 3); two forest species (Tabebuia chrysotricha and Leucaena leucocephala), three levels of composed substrate with sandy soil and vermicompost (v:v) (0% of vermicompost: 100% of soil; 50% vermicompost: 50% of soil; and 25% of vermicompost: 75% of soil), and with 9 replications. The response to the vermicompostaddition was different between both species. The addition of 25% of vermicompost to sandy soil provides greater growth in seedlings of both Tabebuia chrysotricha and Leucaena leucocephala; however, the Leucaena leucocephala plants had greater height, length and specific root surface area than the Tabebuia chrysotricha in the higher doses of vermicompost added to sandy soil.Keywords: vermicompost, organic substrate, soil degradation. DOI: http://dx.doi.org/10.14583/2318-7670.v01n01a06

A sand culture experiment was conducted at the University of Agriculture, Makurdi, Nigeria, in 2001 and 2002, with the objective of determining the appropriate levels of aluminium activity to screen tropically adapted genotypes of soybean for aluminium stress tolerance. Fifteen genotypes of soybean constituted the main plot, while eight levels of aluminium activity (0, 50, 100, 200, 300, 400, 450 and 500 μMAl3+) constituted the subplots in a split-plot design. The experiment was replicated three times. Plants watered with the 500 μMAl3+ treatment got burnt after 3 to 5 days and were removed from the treatment. Data were taken on the root dry weight, shoot dry weight and relative root surface area at 25DAP. Aluminium, genotype and genotype × aluminium interaction effects were all highly significant. Aluminium activity at 300 μMAl3+ level along with the control (0 μMAl3+) were considered as appropriate for root dry weight, while the 450 μMAl3+ level along with the control (0 μMAl3+) were considered as appropriate for shoot dry weight and relative root surface area and recommended for the rapid screening of tropically adapted genotypes of soybean in sand culture in the tropics. The relative root surface area was the most sensitive in discriminating between levels of aluminium activity and should have preference in any selection programme. Key words: Aluminium activity, sand culture screening, tropically adapted genotypes of soybean.

Growth and physiological responses before and after transplanting to a simulated landscape were studied for `East Palatka' holly (Ilex ×attenuata Ashe `East Palatka') grown in plastic containers (PC), in the ground in fabric containers (FC), or in the ground conventionally. At the end of a 15-month production period, trees grown in PC had more shoot dry weight and leaf area than trees grown in FC, and they had thinner trunks than field-grown trees. Root balls on harvested field-grown trees contained 55% and those grown in FC 65% of total-tree root surface area. Trees transplanted from FC had the lowest predawn leaf xylem potential and required more frequent post-transplant irrigation than trees grown in PC or in the ground. Carbon assimilation rate and stomata1 conductance in the first week after transplanting were highest for trees planted from PC. Dry weight of regenerated roots was similar for all production methods 4 months after transplanting from the nursery, but trees grown in PC had SO% more regenerated root length, and the roots extended further into the back-fill soil.

Growth and physiological characteristics were evaluated in autografted and reciprocally grafted plants of Prunus avium L. ×pseudocerasus Lindl. `Colt' and Prunus cerasus L. `Meteor'. Containerized plants were grown for 150 days in a greenhouse under either well-watered or water-stressed conditions. Both the scion and rootstock influenced growth (relative growth rate, R̄), morphological [leaf area : root surface area (LARSA) and specific leaf area (SLA)], and physiological (mean net assimilation rate, Ē) characteristics of grafted plants. Regardless of the watering regime, plants with `Meteor' scions and `Colt' rootstocks maintained higher R̄ than plants with `Colt' scions and `Meteor' rootstocks. This enhanced growth occurred as a result of higher Ē. Measurements on water-stressed plants also showed that the graft combination of `Meteor' on `Colt' had the lowest LARSA, while the reciprocal combination of `Colt' on `Meteor' had the highest. Differences in LARSA among water-stressed plants primarily reflected changes in SLA, as influenced by both rootstock and scion, and not in partitioning of dry weight between these organs.

Com o objetivo de estimar os parâmetros genéticos relativos às qualidades do sistema radicular de candeia, foram utilizadas mudas provenientes de 24 progênies de polinização livre do Parque Estadual Quedas do Rio Bonito em Lavras, MG. Dois meses após a germinação, as imagens das raízes de nove mudas de cada progênie, distribuídas em três classes de tamanho (grande, maiores mudas dentro de cada progênie, médio, mudas médias dentro da progênie e pequeno, mudas em torno de 5 cm), foram obtidas por scanner óptico. Posteriormente, as mesmas raízes foram coradas com corante azul de astra 0,1%, durante 15 min, e novamente analisadas. As leituras indicaram diferenças significativas entre material não-corado e corado, enfatizando o seu uso. Na análise de variância, houve diferenças significativas entre as progênies e entre os tamanhos analisados quanto aos caracteres de raízes: comprimento total, área da superfície, diâmetro médio e número de raízes finas. Os ganhos genéticos esperados com a seleção evidenciaram que esses caracteres devem ser estudados nas mudas grandes, pois apresentam os maiores valores esperados. Seedlings derived from 24 open-pollinated progenies from Quedas do Rio Bonito State Park, Lavras, MG, were used to estimate the genetic parameters concerning the quality of candeia root system. Two months after germination, optical scanning images of new seedling roots were obtained for each progeny, distributed into three size classes (large, medium and small). These roots were stained with 0.1% astra blue for 15 min and then analyzed. The results showed significant differences between stained and non-stained root samples indicating the need for root staining before the analysis. The analysis of variance also showed significant differences among progenies and size classes, which were analyzed considering the following traits: total root length, root surface area, mean diameter and the number of fine roots. The expected genetic gain with selection showed that these traits must be studied in grown seedlings as they showed the largest expected gains.

Summary Removing 4 out of 5 seminal roots from 7-day-old wheat seedlings arrested leaf elongation for 1.5 h. This effect can be explained by an initial decrease in foliar water content resulting from the smaller root surface area available for water uptake. Subsequently, leaf hydration increased with time and came to equal that of intact plants within 2 h. The rehydration was seemingly effected by an increasing conductivity of the one remaining root axis, since transpiration of the partially de-rooted plants did not fall below that of controls. With time, leaf elongation resumed, but at a slower rate than in intact plants. This slower growth may be attributed to a decrease in leaf extensibility since this was found to be reduced when measured by a counterweight technique involving linear displacement transducers. Loss of extensibility was associated with decreased IAA concentration in the leaf elongation zone.