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Background: The application of synthetic chemical inputs in current agricultural practices has significantly increased crop production, but their use has caused severe negative consequences on the environment. Humalite is an organic soil amendment that is rich in humic acid and found in large deposits in southern Alberta, Canada. Humic products can enhance nutrient uptake and assimilation in plants by reducing nutrient losses and enhancing bioavailability in the soil. Aim: Here, we evaluated the effects of different humalite rates in the presence of nitrogen, phosphorus, potassium (NPK) at recommended rates on soil nitrogen availability, wheat growth, grain yield, seed nutritional quality, and nitrogen use efficiency (NUE) under controlled environmental conditions. Methods: A series of studies were conducted by applying five different rates of humalite (0, 200, 400, 800, and 1600 kg ha−1) with NPK at recommended rates. Soil nitrogen availability and shoot and root growth parameters were recorded at flowering stage. NUE was calculated based on the grain yield at maturity stage. Results: Plants grown in the presence of humalite augmented root morphological parameters (root length, volume, and surface area), plant biomass (shoot and root), and nutrient uptake (N, P, K, and S) compared to the plants supplied with recommended fertilizer alone. Furthermore, humalite application significantly increased grain yield (14%–19%), seed protein content (23%–30%), and NUE (14%–60%) compared to the fertilizer application alone. Conclusion: These findings suggest that humalite can be used as an organic soil amendment to reduce synthetic fertilizer application and improve plant growth and yield while enhancing fertilizer use efficiency. [ABSTRACT FROM AUTHOR]

When aboveground materials are harvested for fuel production, such as with Sorghum bicolor, the sustainability of annual bioenergy feedstocks is influenced by the ability of root inputs to contribute to the formation and persistence of soil organic matter (SOM), and to soil fertility through nutrient recycling. Using 13C and 15N labeling, we traced sorghum root and leaf litter‐derived C and N for 19 months in the field as they were mineralized or formed SOM. Our in situ litter incubation experiment confirms that sorghum roots and leaves significantly differ in their inherent chemical recalcitrance. This resulted in different contributions to C and N storage and recycling. Overall root residues had higher biochemical recalcitrance which led to more C retention in soil (27%) than leaf residues (19%). However, sorghum root residues resulted in higher particulate organic matter (POM) and lower mineral associated organic matter (MAOM), deemed to be the most persistent fraction in soil, than leaf residues. Additionally, the overall higher root‐derived C retention in soil led to higher N retention, reducing the immediate recycling of fertility from root as compared to leaf decomposition. Our study, conducted in a highly aggregated clay‐loam soil, emphasized the important role of aggregates in new SOM formation, particularly the efficient formation of MAOM in microaggregate structures occluded within macroaggregates. Given the known role of roots in promoting aggregation, efficient formation of MAOM within aggregates can be a major mechanism to increase persistent SOM storage belowground when aboveground residues are removed. We conclude that promoting root inputs in S. bicolor bioenergy production systems through plant breeding efforts may be an effective means to counterbalance the aboveground residue removal. However, management strategies need to consider the quantity of inputs involved and may need to support SOM storage and fertility with additional organic matter additions. [ABSTRACT FROM AUTHOR]

Massive changes in gene expression occur when plants are subjected to phosphorus ( P) limitation, but the breadth of metabolic changes in these conditions and their regulation is barely investigated. Nearly 350 primary and secondary metabolites were profiled in shoots and roots of P-replete and P-deprived A rabidopsis thaliana wild type and mutants of the central P-signalling components PHR1 and PHO2, and micro RNA399 overexpresser. In the wild type, the levels of 87 primary metabolites, including phosphorylated metabolites but not 3-phosphoglycerate, decreased, whereas the concentrations of most organic acids, amino acids, nitrogenous compounds, polyhydroxy acids and sugars increased. Furthermore, the levels of 35 secondary metabolites, including glucosinolates, benzoides, phenylpropanoids and flavonoids, were altered during P limitation. Observed changes indicated P-saving strategies, increased photorespiration and crosstalk between P limitation and sulphur and nitrogen metabolism. The phr1 mutation had a remarkably pronounced effect on the metabolic P-limitation response, providing evidence that PHR1 is a key factor for metabolic reprogramming during P limitation. The effects of pho2 or micro RNA399 overexpression were comparatively minor. In addition, positive correlations between metabolites and gene transcripts encoding pathway enzymes were revealed. This study provides an unprecedented metabolic phenotype during P limitation in A rabidopsis. [ABSTRACT FROM AUTHOR]

Plant cells contain a wide range of interesting secondary metabolites, which are used as natural pigments and flavoring agents in foods and cosmetics as well as phyto-pharmaceutical products. However, conventional industrial extraction from whole plants or parts of them is limited due to environmental and geographical issues. The production of secondary metabolites from in vitro cultures can be considered as alternative to classical technologies and allows a year-round cultivation in the bioreactor under optimal conditions with constant high-level quality and quantity. Compared to plant cell suspensions, differentiated plant in vitro systems offer the advantage that they are genetically stable. Moreover, the separation of the biomass from culture medium after fermentation is much easier. Nevertheless, several investigations in the literature described that differentiated plant in vitro systems are instable concerning the yield of the target metabolites, especially in submerged cultivations. Other major problems are associated with the challenges of cultivation conditions and bioreactor design as well as upscaling of the process. This article reviews bioreactor designs for cultivation of differentiated plant in vitro systems, secondary metabolite production in different bioreactor systems as well as aspects of process control, management, and modeling and gives perspectives for future cultivation methods. [ABSTRACT FROM AUTHOR]

Summary • The aims were to determine the quantities of tissue cadmium (Cd) bound in maize (Zea mays ) roots through phytochelatin-based complexes with changes in time of exposure, the concentration of Cd, the part of the primary root system, and the status of the complexes in shoots. • Six buffer extractions solubilized most tissue Cd and a rapid small-scale gel filtration resolved the buffer soluble Cd into high and low molecular weight Cd-binding complexes. • Six buffer extractions, rather than one, effectively represented high and low molecular weight phytochelatin-based Cd-binding complexes. The low molecular weight complex predominated in root apices and after 1 d of 3 µm Cd; the high molecular weight complex predominated in mature root parts and after 2 d of exposure. More tissue Cd was bound by both complexes with increasing time of exposure and concentration of Cd. Buffer extracted less Cd from shoots than roots and phytochelatin-based complexes bound less shoot Cd (29% vs 88%). • The phytochelatin-based complexes are in a dynamic state dependent on the treatment and they function to bind variable amounts of tissue Cd. [ABSTRACT FROM AUTHOR]

One alkaline invertase and two acid invertase activities were detected in the shoots of etiolated rice (Oryza sativa) seedlings. The alkaline invertase (AlT) was purified to homogeneity through steps of ammonium sulphate fractionation, concanavalin A-Sepharose affinity chromatography (non-retained), DEAE-Sephacel chromatography and preparative electrophoresis. The pH optimum of AIT was 7.0 and the molecular mass, determined by gel filtration, was 240 kDa. It is apparently a homotetrameric enzyme (subunit molecular mass 60 kDa). The isoelectric point was 4.4 by isoelectric focusing. The best substrate of the enzyme was sucrose, with a Km of 2.53 mM. The enzyme also hydrolysed raffinose, but not maltose or lactose, so it is a β-D-fructofuranosidase. It gave negative glycoprotein staining, Of the hydrolysis products. fructose was a competitive inhibitor and glucose was a non-competitive inhibitor. Treatment with an alkaline phosphatase could activate AIT, whereas other proteins such as BSA, concanavalin A and urease had no effect on the enzyme activity. The enzyme activity was inhibited by Tris, thiol reagents and heavy metal ions. [ABSTRACT FROM AUTHOR]

Although use of embryonic or seedling tissues for mass clonal micropropagation in vitro in conifer reforestation programmes is questionable, there is a potential application in the regeneration of plants from scarce and costly seed derived from controlled pollination. In addition, in vitro culture shortens considerably the lag phase in numbers during the initial stages of vegetative propagation via rooted cuttings. Successive steps of the present technique are described whereby cotyledonary needles (secondary explants) were subcultured on a hormone-free medium after administration of cytokinin or auxin to 14-day-old seedling (primary) explants of Picea abies. For bud induction, N6-benzyladenine (BA) was applied either as a short duration (3 h), high-concentration (125 μM) pulse or by vacuum infiltration and incubation in a BA-containing (5 μM) infusion medium. Induced adventitious shoots were elongated with the aid of far-red light and rooted in vivo after along-duration (12 h), high-concentration (625 μM) application of indolebutyric acid. Pulse and infusion treatments resulted in the induction of greater numbers of adventitious buds (average of 12 per needle) over a three to four week shorter culture period than was the case with the conventional inclusion of growth regulators. in the agarified medium. No exogenous auxin was required in the bud-induction programme; its inclusion even at nanomolar levels promoted histo- rather than morphogenesis. In cotyledonary needles, to the primary explants of which BA was applied as a pulse or by infusion, the cell divisions which gave rise to the meristemoids from which adventitious buds were produced, appeared to commence mainly in undifferentiated hypodermal layer cells but also in the mesophyll immediately below. By contrast, where BA was incorporated in the agarified medium the first divisions occurred mainly in cells of the epidermal layer. A number of factors affected plantlet regeneration, for instance seed variability, age of seedlings, and mode of application of growth substances. It should also be accepted that the xeromorphic nature of the conifer leaf might impose physiological and morphological constraints on its culture in vitro that could militate against easy morphogenic manipulation. It is deemed essential that the current mean ratio of regenerated plants to cotyledonary needles of 1:1 be increased 10 to 20 fold in order to approach commercial feasibility. [ABSTRACT FROM AUTHOR]

Gibberellins GA1, GA8, GA19, GA29, GA20 and GA56,(2-epi-GA8), were identified by combined gas chromatography-mass spectrometry in root extracts of elongating Salix pentandra L. seedlings. The presence of GA8 was also demonstrated for the first time in S. pentandra shoots. The levels of GA1, GA8, GA19, GA20 in shoot tissue and in roots were estimated by selected ion monitoring. While the amounts of GA8 and GA19 were similar in both plant parts, the levels of the biologically active GA1 and its immediate precursor GA20, were found to be much lower in roots than in shoots. [ABSTRACT FROM AUTHOR]

Twenty day-old winter rape (Brassica napus L. var. oleifera L. cv. Jantar) seedlings, grown in nutrient solution, were exposed to different shoot/root temperature (i. e. 20/20, 20/3, 3/20 and 3/3°C) for 2 or 4 weeks. Chilling treatments modified markedly the pattern of plant growth as indicated by changes in dry matter accumulation in individual plant parts (leaves, hypocotyls, roots) and decreased leaf specific area. Growth of roots was less sensitive to low temperature than that of shoots. This was reflected by a decrease in shoot/root biomass ratio. Chilling treatments increased freezing resistance, decreased water content and water potential and modified reducing sugar, soluble protein and phospholipid contents in the leaves. A biphasic character of tissue responses to chilling temperature was observed, the most remarkable changes being registered during the first 7 or 14 days of the treatment. Effects of root or shoot exposure to chilling temperature on ice nucleation temperature, LT50, water potential, accumulation of sugars and phospholipids in leaves were additive. All the observations point to the important role of the root system in plant acclimation to cold. Its impact on water status of leaves is emphasized and some mechanisms of root involvement in acclimation processes are proposed. [ABSTRACT FROM AUTHOR]

The hormones auxin and cytokinin are essential for plant growth and development. Because of the central importance of root and shoot apical meristems in plant growth, auxin/cytokinin interactions have been predominantly analyzed in relation to apical meristem formation and function. In contrast, the auxin/cytokinin interactions during organ growth have remained largely unexplored. Here, we show that a specific interaction between auxin and cytokinin operates in both the root and the shoot where it serves as an additional determinant of plant development. We found that auxin at low concentrations limits the action of cytokinin. An increase in cytokinin level counteracts this inhibitory effect and leads to an inhibition of auxin signaling. At higher concentrations of both hormones, these antagonistic interactions between cytokinin and auxin are absent. Thus, our results reveal a bidirectional and asymmetrical interaction of auxin and cytokinin beyond the bounds of apical meristems. The relation is bidirectional in that both hormones exert inhibitory effects on each other's signaling mechanisms. However, this relation is also asymmetrical because under controlled growth conditions, auxin present in nontreated plants suppresses cytokinin signaling, whereas the reverse is not the case. [ABSTRACT FROM AUTHOR]