Muhammad Yasin Ashraf

Inoculating wheat seedlings with exopolysaccharide-producing bacteria restricts sodium uptake and stimulates plant growth under salt stress

A pot experiment was conducted to elucidate the effects of inoculating five exopolysaccharide- (EPS-) producing bacterial strains on the dry matter yield and the uptake of K+, Na+, and Ca2+ by wheat seedlings grown in a moderately saline soil. The bacteria were isolated from the rhizosphere soil (RS) of wheat grown in a salt-affected soil and included Aeromonas hydrophila/caviae (strain MAS-765), Bacillus insolitus (strain MAS17), and Bacillus sp. (strains MAS617, MAS620 and MAS820). The inoculation substantially increased the dry matter yield of roots (149–527% increase) and shoots (85–281% increase), and the mass of RS (176–790% increase). All the strains, except MAS617, also increased the RS mass/root mass ratio as well as the population density of EPS bacteria on the rhizoplane, and both these parameters were significantly correlated with the content of water-insoluble saccharides in the RS. Inoculation restricted Na+ uptake by roots, which was not attributable to the binding of Na+ by the RS, or to the ameliorative effects of Ca2+ under salinity. The decreased Na+ uptake by roots of inoculated than uninoculated plants was probably caused by a reduced passive (apoplasmic) flow of Na+ into the stele due to the higher proportion of the root zones covered with soil sheaths in inoculated treatments. Among the strains tested, MAS820 was the most efficient in all respects, whereas MAS617 was the least effective. Results suggested that inoculating selected EPS-producing bacteria could serve as a useful tool for alleviating salinity stress in salt-sensitive plants.

Salt-Induced Changes in Two Canola Cultivars Differing in Salt Tolerance

Responses of 20 d-old plants of two Brassica napus L. cultivars Dunkeld and Cyclon to NaCl salinized soil [electrical conductivity 2.4 (control), 4.0, 8.0 or 12.0 dS m−1] were examined. The salt tolerant line Dunkeld had significantly higher fresh and dry masses of shoots, and seed yield than salt sensitive line Cyclon in all salinities. The effect of salt stress on reduction in total leaf soluble sugars was markedly greater in Dunkeld as compared to that in Cyclon. No effect of salt stress was observed on leaf soluble proteins but there was a slight increase in total free amino acids of both cultivars. Leaf proline content increased markedly in both cultivars and Dunkeld had greater proline content than Cyclon at all salinities. Salt stress had no significant effect on seed oil content and erucic acid content of seed oil, however, content of glucosinolates in the seed meal increased and Cyclon had greater content of glucosinolates than Dunkeld.

Salinity induced changes in α-amylase activity during germination and early cotton seedling growth

Salinity induced changes in α-amylase activity in three cotton cultivars (NIAB-Karishma, NIAB-86 and K-115) was studied during germination and early seedling growth under controlled conditions. The increase in NaCl concentration resulted in the decrease in α-amylase activity and break down of starch into reducing and non-reducing sugars in all cultivars, however, it was more pronounced in NIAB-86. K-115 showed highest germination followed by NIAB-Karishma and NIAB-86.

Effect of selenium foliar spray on physiological and biochemical processes and chemical constituents of wheat under drought stress

Selenium (Se) is considered an essential micronutrient for humans, animals and plants due to its physiological and antioxidative properties. The positive role of Se in attenuation of drastic effects of various environmental stresses in plants is, however, still unclear and need to be explored. The present study aimed at investigating the physiological and biochemical changes induced by Se foliar spray to improve the drought tolerance potential of wheat. Additionally, we also examined the effect of supplemental Se on uptake of nutrients using detection by ICP-OES. Foliar Se application significantly lowered osmotic potential (13%) that markedly improved turgor by 63%, enhanced transpiration rate (60%), improved accumulation of total soluble sugars (33%) and free amino acids (118%) and activity of antioxidant system which ultimately increased the grain yield by 24%. Supplemental Se also significantly increased Se contents (5.77µgg(-1)DW) and improved Fe (91%) and Na (16%) uptake, whereas it reduced Zn accumulation by 54% and did not affect Ca contents. The results supported our hypothesis that supplemental Se influences nutrients uptake and wheat yield through maintenance of turgor and gas exchange characteristics and enhancement in antioxidant system activity.

Alleviation of waterlogging stress in upland cotton (Gossypium hirsutum L.) by exogenous application of potassium in soil and as a foliar spray

The effectiveness of exogenous application of K in ameliorating the adverse effects of waterlogging on cotton plants was assessed under greenhouse conditions. Forty-day-old plants were subjected to continuous flooding for 1 week and then K (60 kg ha–1) was applied either as soil application, foliar spray, or in combination. The waterlogging treatment significantly reduced plant height and fresh and dry biomass, photosynthetic pigments, gas exchange parameters and nutrient accumulation (N, K+, Ca2+) in stem, root and leaves of cotton plants, Although Mg2+ content in roots increased significantly due to waterlogging, it was not affected in stem or leaves. In contrast, Mn2+ and Fe2+ contents generally increased under waterlogged conditions. All water relation parameters were also significantly influenced by waterlogging stress. Waterlogged plants supplemented with K showed a significant improvement in growth, photosynthetic pigments and photosynthetic capacity. Potassium supplementation also improved nutrient uptake of waterlogged plants and resulted in significantly higher accumulation of K+, Ca2+, N, Mn2+ and Fe2+ than those plants not supplied with K. Although all modes of K application were effective in mitigating the inhibitory effects of waterlogging, the combined application through soil + foliar spray yielded the best results and the foliar application (alone) being the least effective.

Supplemental selenium improves wheat grain yield and quality through alterations in biochemical processes under normal and water deficit conditions

The paper mainly reported the effects of exogenous selenium (Se) supply (Se seed priming, Se fertigation and Se foliar spray) on physiological and antioxidant system of wheat aiming to clarify its effect on yield and nutritional quality of wheat under both normal and water deficit conditions. Water stress markedly decreased the grain Se, iron (Fe), phosphorous (P), zinc (Zn) and magnesium (Mg) contents. Supplemental Se (Na2SeO4) improved the yield and quality of water stressed plants due to enhancement in the production of osmoprotectants and increased activity of antioxidant enzymes. The foliar spray of Se was more effective than Se fertigation and Se seed treatment. To the best of our knowledge, this is the first elaborate study that involved various Se application methods to evaluate the efficiency of Se supply to plants that would be crucial to develop better understanding of Se translocation and accumulation within crop plants under drought stress.

Availability of soil and fertilizer nitrogen to wetland rice following wheat straw amendment

SummaryA pot experiment was conducted to study the availability of soil and fertilizer N to wetland rice as influenced by wheat straw amendment (organic amendment) and to establish the relative significance of the two sources in affecting crop yield. Straw was incorporated in soil at 0.1, 0.2, and 0.3% before transplanting rice. Inorganic N as 15N-ammonium sulphate was applied at 30, 60, and 90 μg g-1 soil either alone or together with wheat straw in different combinations. After harvesting the rice, the plant and soil samples were analyzed for total N and 15N. Straw incorporation significantly decreased the dry matter and N yield of rice, the decrease being greater with higher rates of straw. The reduction in crop yield following the straw incorporation was attributed mainly to a decrease in the uptake of soil N rather than fertilizer N. The harmful effects of organic matter amendment were mitigated by higher levels of mineral N addition. The uptake of applied N increased and its losses decreased due to the straw incorporation. Mineral N applied alone or together with organic amendment substantially increased the uptake of unlabelled soil N. The increase was attributed to a real added N interaction.

Influence of water stress and exogenous glycinebetaine on sunflower achene weight and oil percentage

The study was carried out to assess whether exogenously applied glycinebtaine has any role in reducing the adverse effects of water stress on sunflower achene yield and oil contents. Two sunflower lines, Gulshan-98 and Suncross were subjected to water stress at the vegetative and reproductive stages of plant growth. Three levels of glycinebtaine (0, 50 and 100 mM) were applied before sowing (seed treatment) and at the time of initiation of stress at the vegetative and reproductive stages. A marked adverse effect of water stress on 100-achene weight and achene oil contents were observed in both sunflower lines. Exogenous supply of glycinebtaine was not effective in alleviating the adverse effects of water stress on achene oil percentage. Foliar spray of glycinebtaine, however, significantly reduced the negative effects of water stress on achene weight. Seed treatment with either level of glycinebtaine was not effective in increasing the 100-achene weight and achene oil percentage under both normally irrigated and water stress conditions. The sunflower line, Suncross produced higher oil yield than that of Gulshan-98.

Time-course changes in the inorganic and organic components of germinating sunflower achenes under salt (NaCl) stress

Abstract Achenes of sunflower (cv Hi-Corn) were subjected for seven days to salinized solution culture containing 0, 50, 100 or 150 mol NaCl m −3 . Fresh weights of cotyledons and hypocotyl increased at all external salt regimes, although the increase was low at the highest salt level. Na + , Cl − and Ca 2+ concentrations in hypocotyls increased with time in all salt treatments. The external salt concentration or the time of incubation had no significant effect on Na + , K + and Ca 2+ concentration of cotyledons, but in contrast, there was a significant time course increase in Cl − level upon addition of salt to the rooting medium; this was not the case with the hypocotyl Cl − accumulation. A gradual decrease of soluble proteins with time was noted in cotyledons, but addition of salt was without any effect. By contrast, the hypocotyl soluble proteins decreased consistently with increasing salt level. There was no significant effect of NaCl on free amino acids level of cotyledons up to the 5 th day of germination, but thereafter, cotyledonary free amino acids decreased considerably with increased salt level. There was a time-course decrease in soluble sugars of cotyledons and hypocotyl in control and at 50 mol NaCl m −3 , but at higher NaCl concentrations soluble sugars in the hypocotyl increased with time. Total lipids of cotyledons decreased significantly with time. The salt effect on germination of sunflower was found to be associated with a time-course dependend absorption of Na + and Cl − by the hypocotyl. In addition, the deleterious effect of salt on seed germination could be ascribed to impairment in breakdown of seed lipids thereby diminishing the supply of soluble sugars to the growing embryonic tissues.

Nitrate Reduction and Nutrient Accumulation in Wheat Grown in Soil Salinized with Four Different Salts

ABSTRACT The effect of salinization of soil with Na2SO4, CaCl2, MgCl2, and NaCl (70:35:10:23) on the biochemical characteristics of three wheat (Triticum aestivum L.) cultivars (‘LU-26S,’ ‘Sarsabaz’ and ‘Pasban-90’) was investigated under natural environmental conditions. Twenty-day-old seedlings of all three cultivars were subjected to three salinity treatments: 1.3 (control), 5.0, and 10 dSm−1 for the entire life period of plants. After 120 d of seed sowing, plant biomass production decreased by 49% and 65%, respectively, in response to 5 and 10 dSm−1 salinity levels. Addition of salts to growth medium also had a significant adverse effect on plant height. Increasing salinity treatments caused a great reduction in nitrate reductase activity (NRA) of the leaf. The inhibitory effect of salinity on nitrate reduction rate was more pronounced at the reproductive stage than at the vegetative stage of plant growth. Wheat cultivars ‘LU-26S’ and ‘Sarsabaz’ showed less reduction in NRA due to salinity compared with ‘Pasban-90.’ Ascending salinity levels significantly reduced potassium (K+) and calcium (Ca2+) accumulation in shoots, while the concentration of sodium (Na+) was increased. Salts of growth medium increased the shoot nitrogen (N) concentration, whereas phosphorous (P) concentration of shoots was significantly reduced due to salinity. Wheat cultivars ‘LU-26S’ and ‘Sarsabaz’ proved to be the salt-tolerant ones, producing greater biomass, showing less reduction in NRA, maintaining low sodium (Na+), and accumulating more K+ and Ca2+ in response to salinity. These two cultivars also showed less reduction in shoot K+/Na+ and Ca+/Na+ ratios than in ‘Pasban-90,’ particularly at the 10 dSm−1 salinity level.