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From the early 2000s there has been a general shift in South Africa in harvesting and extraction systems from the use of semi- to fully-mechanised systems. Any increase in mechanisation, as is occurring in Zululand, will need to take into consideration damage to stumps and the subsequent ability to regenerate by coppice. In 2002, four types of harvesting and extraction systems, arranged in a randomised complete block design, were used to clearfell a stand ofE. grandis×E. urophylla. A motor-manual harvesting system was used to carry out the manual harvesting system (Man). The fully mechanised system (Mech) consisted of a single-grip harvesting head used with a tracked excavator to carry out all felling and processing operations. Two additional systems (Man_Mech_3W and Man_Mech_Flexi) had increased levels of mechanisation over that of the Man treatment. Both these harvesting systems made use of a Bell debarker, with loading carried out by a Bell three-wheeled loader in the Man_Mech_3W, and by a Flexiloader in the Man_Mech_Flexi treatments.Data collected from these four treatments were used to determine the effects of mechanised harvesting systems on type and severity of stump damage, coppicing potential and coppice growth over the rotation. Irrespective of harvesting system, more damage occurred to the top than bottom half of the stump, with a significant decrease in coppice regrowth with increasing stump damage. Most damage and least coppice regrowth occurred in the extraction rows where the damage recorded could be attributed to vehicle movement, tear-outs and/or log stripping. There was no significant difference between the harvesting systems in terms of stump mortality, final stem stocking and rotation-end volume. Thus, individual components within each harvesting system can have a larger impact than the overall harvesting system used. Future research should focus on these components, and where associated damage occurs for a specific component, this should be lessened through management intervention, training or technological improvements. [ABSTRACT FROM PUBLISHER]

Since the fate of nanoparticles after their release in the environment and their possible transfer in plants and subsequent impacts is still largely unknown, this paper evaluates the potential phytotoxic effects of up to 20% w/w TiO2nanoparticles (nTiO2) on barley cultivated in hydroponics and agar media. The X-ray diffraction analysis confirmed thatnTiO2powder corresponds to anatase phase. On agar medium only high concentrations ofnTiO2(10% and 20% w/w) induced significant inhibition of shoot growth. However, hydroponics treatment withnTiO2up to 1000 mg L−1did not show any adverse effect on the shoot growth. In both experiments, (i) root growth inhibition effects became visible with increasing concentration ofnTiO2, (ii) plants treated withnTiO2showed no change in chlorophyllaandbcontent, even though the plants absorbednTiO2, (iii) weight of biomass treated withnTiO2was not significantly different compared to control. Therefore, we assume that transport ofnTiO2into the aerial parts is limited due to the presence of effective mechanical or physiological barriers in roots. Overall, it appears that early root growth is a relevant indicator of potential effects ofnTiO2exposure. Our results also indicate that synthesizednTiO2are not significantly toxic to the barley when applied at the concentrations used in this work, even though plants absorb titanium. [ABSTRACT FROM AUTHOR]

Senecio inaequidensis a neophyte originating from South Africa that has managed to spread to Europe and colonize large areas. This plant has toxic pyrrolizidine alkaloids (PAs) that represent a health risk to humans and animals. The aim of this work was to measure the content of PAs of these plants in continuous intervals over the entire growing season. The plants were separated into their organs, such as sprouts, stems, leaves and inflorescences. PAs were extracted from the dried plants using an acidic methanol solution, purified and measured by GC/MS. The average PA content of plants over the growing season was 0.33% of dry weight. The highest PA levels were about 1% in the dry weight and were found in the young sprouts and flower heads. There were nine PAs present, of which six could be identified. The main alkaloid was retrorsine followed by senecivernine, senecionine, integerrimine, usaramine and seneciphylline. Due to the high PA content of the inflorescences, the long flowering period and the rapid invasion dynamics, this species presents a high health risk for humans and animals. [ABSTRACT FROM PUBLISHER]

Salinity effects on growth and essential oil composition of Tunisian safflower (Carthamus tinctorius) shoots grown in hydroponic medium were investigated. Plants treated with 25 mM NaCl showed remarkable morphological modifications and decrease in shoot dry matter. Under 50 and 75 mM NaCl, plants showed a withering and a drastic reduction in dry matter (50% and 70%, respectively). Under NaCl 25 mM, essential oil yield increased significantly (p<0.05) up to 70% and 27% respectively in plants from Tazarka and Kairouan provenances compared with the control. The major compound in Tazarka essential oil was found to be 1,8-cineole (23.5%) followed by methyl eugenol (18.0%), 1-pentadecene (9.1%) and camphene (9.0%). In plants from Kairouan provenance, the major compounds were 1-pentadecene (22.9%), methyl-eugenol (11.8%), linalool (8.1%) and camphene (7.9%). Whatever the origin, the application of 25 mM resulted in remarkable changes in the content and the percentage of the main oil components with the effect being more pronounced in plants from Tazarka. [ABSTRACT FROM AUTHOR]

Yield loss in potato damaged by hail is mainly caused by reduced leaf area and plant stand. A 2-year field experiment was conducted to investigate the effect of simulated hail damage on potato yield. The treatments were six levels of defoliation (control, 20, 40, 60, 80 and 100%) and five defoliation times (2, 5, 8, 11 and 14 weeks after emergence). The experiment was set up in a randomized block design with four replications, and the treatments were arranged as a factorial. From the perspective of yield loss, the most important time of defoliation, for mild and intense defoliation, respectively, were 8–11 and 5–11 weeks after emergence. The period between 5 and 8 weeks includes the stages of tuber initiation and tuber growth; the stages most sensitive to removal of aerial parts. Regardless of defoliation intensity, the production of small potatoes mostly occurred when defoliation occurred at 2 and 5 weeks. Plants were able to recover from any level of defoliation if it occurred at an early stage. In summary, yield reduction was little influenced by intensity of defoliation, but the timing of defoliation was evidently the most important factor. [ABSTRACT FROM AUTHOR]

Effects of salt [sodium chloride (NaCl): sodium sulfate (Na2SO4)] and alkali [sodium bicarbonate (NaHCO3): sodium carbonate (Na2CO3)] stresses on biomass and the contents of organic acids (OAs) components in wheat shoots and roots were compared. Both stresses inhibited the growth of wheat seedlings, the effect on roots biomass was higher than that on shoots, and more severe for alkali than for salt stress. Compared to salt stress, OAs are the special physiological responses of wheat seedlings to alkali stress. The total OAs contents in shoots increased significantly with increasing alkalinity, but only increased as alkali stress supply increased from 0 to 80 mM in roots, then decreased. Roots were more sensitive than shoots responding to alkali stress. High alkalinity destroyed cell membrane of root leading to organic acids efflux from roots. Among the OAs components, citrate and malate were the key components in wheat shoots and roots when responding to alkali stress. [ABSTRACT FROM AUTHOR]

Mercury (Hg) contaminated soils from Oak Ridge, Tennessee were investigated for phytoavailability of mercury as measured by degree of Hg translocation in aboveground biomass of Impatiens walleriana plants grown in the soils. After 90 days of incubation, results revealed a higher concentration of total Hg in the leaves than in the flowers or the stems. Plants that were grown in the soils with higher Hg concentrations showed significantly higher Hg uptake and translocation in the aboveground plant-biomass, and the correlation with the initial soil-Hg was significant for the leaves and the stems in the plants that were tested. On an average, only 4.06 μg of Hg could be found in the above ground plant biomass of all the plants, compared to an average 3673.50 μg of initial total Hg concentrations in these soils. Statistical analysis revealed a greater affinity of Hg for the soil carbon, which supported the finding of this study on low soil Hg bioavailability. [ABSTRACT FROM AUTHOR]

The effects of sugar type, activated charcoal, and naphthalene acetic acid on the propagation of pistachio (Pistacia vera) in vitro were investigated. Length of roots increased up to 30% when sucrose was used instead of maltose and up to four times when 2 g/L of activated charcoal was added to the medium. The number of adventitious shoots was enhanced (up to 3.2 shoots) when a Rugini and Verma medium supplemented with 0.75 mg/L naphthalene acetic acid, 0.75 mg/L indole acetic acid, and 2 mg/L 6-benzyl amino purine was used. To enhance rooting of shoots in vitro, we developed a technique to increase the amount of hormones available to the growing shoots. The hormones were delivered using a sterilized fine needle to the base of the growing shoots. This technique enhanced rooting up to 3 times (73%) especially when the hormone indole butyric acid was used as a growth regulator. [ABSTRACT FROM AUTHOR]

The effect of temperature on the growth rate of shoots and roots for seven grass species was investigated in a growth chamber experiment. The following species were tested: Alopecurus pratensis L, Deschampsia caespitosa L (PB), Festuca pratensis Huds, Festuca rubra L, Lolium perenne L, Poa pratensis L and Phleum pratense L. Plants were grown in pots in a greenhouse, then placed in three growth chambers (9/5, 13/9 and 17/13 day/night °C) when the seedlings were two weeks old (5-8 cm high) or five weeks old (14-37 cm high). The young seedlings responded immediately to different temperatures and grew more slowly in the colder growth chambers. Shoot growth of the older plants was similar at all temperatures. Percentage of root was significantly affected by temperature at both growth stages. The results of this experiment indicate that growth of temperate grasses in early growth stages is more dependent on temperature than at later stages. [ABSTRACT FROM AUTHOR]