Shoot

About: Shoot is a research topic. Over the lifetime, 32188 publications have been published within this topic receiving 693348 citations.

Effects of nitrogen and phosphorus deficiencies on levels of carbohydrates, respiratory enzymes and metabolites in seedlings of tobacco and their response to exogenous sucrose

Abstract: A simple method of growing plants in agar was exploited to investigate the effect of long-term nitrogen (N) and phosphorus (P) deficiencies on respiratory metabolism and growth in shoots and roots of Nicotiana tabacum seedlings, and their interaction with exogenously supplied sucrose. Levels of hexose phosphates and 3-phosphoglyceric acid (3-PGA) were low in P-deficient shoots and roots and high in N-deficient shoots and roots. The ratio of hexose phosphates to 3-PGA and levels of fructose-2,6-bisphosphate were high in P-deficient plants and low in N-deficient plants. These data reflect differences in the way metabolism was perturbed, yet both deficiencies were associated with increased root growth relative to shoot growth, starch accumulation in the shoots, and soluble carbohydrate accumulation, especially hexoses, in the roots. Enzymes for sucrose degradation (sucrose synthase, acid and alkaline invertase) and glycolysis (phosphofructokinase, pyrophosphate-dependent phospho-fructokinase and pyruvate kinase) remained unaltered or declined in the shoots and roots. The accumulation of hexoses in roots of N- and P-deficient plants may result from maintenance of high invertase activities relative to sucrose synthase and glycolytic enzymes in the roots. The possibility that hexose accumulation may drive preferential root growth osmotically in N and P deficiencies is discussed. The addition of sucrose to roots to further investigate the interaction of carbohydrates with growth and allocation in low N and low P produced clear effects even though endogenous levels of soluble carbohydrate were already high in the nutrient-deficient plants. In complete nutrition, growth was stimulated, protein content particularly of the roots was increased and there was a preferential increase in activity of sucrose synthase in roots. At low P, enzyme activities in roots were increased, including sucrose synthase, and protein content increased, particularly in the roots, but there was no increase in growth. In N-deficient plants, exogenous sucrose led to decreased protein, Rubisco and chlorophyll content in shoots, in contrast to the other conditions, and a higher protein content and a general increase of catabolic enzyme activities and growth in the roots.

Effects of Drought Stress on Growth and Yield of Rice (Oryza sativa L.) Cultivars and Accumulation of Proline and Soluble Sugars in Sheath and Blades of Their Different Ages Leaves

Abstract: One of the main problems of rice cultivation and production is the lack of water resources, especially during periods of low rainfall which affect the vegetative growth rate and the amount of yield. In this study the effect of low water supply on the number of heading per hill, number of grain per hill, dry weight of vegetative tissues and panicle and 1000 grain weight in three new cultivars of rice including 216, 829 and Zayandeh-Rood were measured under submerged and non-submerged conditions in a randomize complete block design with three replicates. Simultaneously, the variation in proline and total sugars in sheaths and blades of leaves at different ages was determined. The data indicated that Zayandeh-Rood cultivar showed the lowest reduction in shoot dry weigh and the number of tillers per hill under non-submerged conditions. Furthermore, the panicle weight and the number of filled grains per spike were higher in Zayandeh-Rood cultivar than the other cultivars. In addition, the result of this study show that Zayandeh-Rood cultivar in which originated from local cultivars, have higher ability in solute accumulation such as proline and total carbohydrates than the other new lines. Due to correlation between drought tolerance of Zayandeh-Rood and solute accumulation, it may be suggested that the solute accumulation is one of the mechanisms for drought tolerance in rice.

Differential activity of autochthonous bacteria in controlling drought stress in native Lavandula and Salvia plants species under drought conditions in natural arid soil.

Abstract: The effectiveness of autochthonous plant growth-promoting rhizobacteria was studied in Lavandula dentata and Salvia officinalis growing in a natural arid Mediterranean soil under drought conditions. These bacteria identified as Bacillus megaterium (Bm), Enterobacter sp. (E), Bacillus thuringiensis (Bt), and Bacillus sp. (Bsp). Each bacteria has different potential to meliorate water limitation and alleviating drought stress in these two plant species. B. thuringiensis promoted growth and drought avoidance in Lavandula by increasing K content, by depressing stomatal conductance, and it controlled shoot proline accumulation. This bacterial effect on increasing drought tolerance was related to the decrease of glutathione reductase (GR) and ascorbate peroxidase (APX) that resulted sensitive indexes of lower cellular oxidative damage involved in the adaptative drought response in B. thuringiensis-inoculated Lavandula plants. In contrast, in Salvia, having intrinsic lower shoot/root ratio, higher stomatal conductance and lower APX and GR activities than Lavandula, the bacterial effects on nutritional, physiological and antioxidant enzymatic systems were lower. The benefit of bacteria depended on intrinsic stress tolerance of plant involved. Lavadula demonstrated a greater benefit than Salvia to control drought stress when inoculated with B. thuringiensis. The bacterial drought tolerance assessed as survival, proline, and indolacetic acid production showed the potential of this bacteria to help plants to grow under drought conditions. B. thuringiensis may be used for Lavandula plant establishment in arid environments. Particular characteristic of the plant species as low shoot/root ratio and high stomatal conductance are important factors controlling the bacterial effectiveness improving nutritional, physiological, and metabolic plant activities.

Effect of Salts on Germination of Seeds and Growth of Young Plants of Hordeum vulgare, Triticum aestivum, Cicer arietinum and Brassica juncea

Abstract: A greenhouse experiment was conducted on four crop plants in the western region of Gujarat State, India to assess their responses to increasing levels of soil salinity. Of the four crop plants tested (Hordeum vulgare, barley; Triticum aestivum, wheat; Cicer arietinum, gram and Brassica juncea, mustard), barley appeared to be the most tolerant to salinity with regard to seed germination and early growth of the plants. Wheat, gram and mustard were tolerant only to low soil salinity. However, high salt concentrations in the soil reduced the absorption of nitrogen and phosphorus by the young plants. The imbalance of mineral nutrients resulted in a reduction or an inhibition of plant growth. High salinity also caused burning symptoms on the leaves and shoot apices of barley.

Regulation of Plant Growth, Photosynthesis, Antioxidation and Osmosis by an Arbuscular Mycorrhizal Fungus in Watermelon Seedlings under Well-Watered and Drought Conditions

Abstract: Drought stress has become an increasingly serious environmental issue that influences the growth and production of watermelon. Previous studies found that arbuscular mycorrhizal (AM) colonization improved the fruit yield and water use efficiency (WUE) of watermelon grown under water stress; however, the exact mechanisms remain unknown. In this study, the effects of Glomus versiforme symbiosis on the growth, physio-biochemical attributes, and stress-responsive gene expressions of watermelon seedlings grown under well-watered and drought conditions were investigated. The results showed that AM colonization did not significantly influence the shoot growth of watermelon seedlings under well-watered conditions but did promote root development irrespective of water treatment. Drought stress decreased the leaf relative water content and chlorophyll concentration, but to a lesser extent in the AM plants. Compared with the non-mycorrhizal seedlings, mycorrhizal plants had higher non-photochemical quenching values, which reduced the chloroplast ultrastructural damage in the mesophyll cells and thus maintained higher photosynthetic efficiency. Moreover, AM inoculation led to significant enhancements in the enzyme activities and gene expressions of superoxide dismutase, catalase, ascorbate peroxidase, glutathione reductase, and monodehydroascorbate reductase in watermelon leaves upon drought imposition. Consequently, AM plants exhibited lower accumulation of MDA, H2O2 and [Formula: see text] compared with non-mycorrhizal plants. Under drought stress, the soluble sugar and proline contents were significantly increased, and further enhancements were observed by pre-treating the drought-stressed plants with AM. Taken together, our findings indicate that mycorrhizal colonization enhances watermelon drought tolerance through a stronger root system, greater protection of photosynthetic apparatus, a more efficient antioxidant system and improved osmoregulation. This study contributes to advances in the knowledge of AM-induced drought tolerance.