Plant physiology

About: Plant physiology is a research topic. Over the lifetime, 1537 publications have been published within this topic receiving 72038 citations.

Calystegia soldanella: dune versus laboratory plants to highlight key adaptive physiological traits

Abstract: Coastal plants live in heterogeneous and potentially stressful environments in which multiple stress factors may coexist. Some of these constraints can induce oxidative stress with consequent damage to cell components and structures. To contrast oxidative damage plants have evolved antioxidant systems, including both enzymatic and non-enzymatic molecules. The aim of this study was to highlight main physiological traits evolved by plants to survive in coastal environment through a comparison of nutritional and physiological parameters between dune (DC) and laboratory-grown (LC) plants of Calystegia soldanella (L.), a typical dune plant. In comparison with laboratory plants, dune plants living on a soil with relatively low nutrient content, were characterised by lower total nitrogen, K+ and phosphate content and by lower K+/Na+, PO4 2−/Cl− and N/Cl− ratios. Pigment content was significantly higher in LC than in DC plants. Despite their higher hydrogen peroxide content and lipid peroxidation, dune plants had a membrane damage, assessed by the electrolytic conductivity method, not significantly different from that of LC plants. Phenol and ascorbate pools, glutathione reductase and catalase activities were significantly higher in dune than in laboratory plants. Although the stress level was high, coastal plants were well protected against oxidative damage and proline, phenols, ascorbate, glutathione reductase and catalase seemed to play a pivotal role in plant adaptation to the constraints of coastal environment.

Antioxidant enzymatic protection during tobacco leaf ageing is affected by cytokinin depletion

Abstract: Plant ageing and senescence are associated with increased levels of reactive oxygen species. Level of cytokinins, the apparent inhibitors of plant senescence, is controlled by their irreversible degradation catalysed by cytokinin oxidase/dehydrogenase (CKX). We investigated the CKX activity, cytokinin concentration, and activities of antioxidative enzymes in tobacco (Nicotiana tabacum L. cv. Samsun NN) overexpressing the Arabidopsis gene for AtCKX2, targeted for extracellular secretion pathway. The control and AtCKX2 plants differed substantially in their phenotypes. When the lowest leaves in controls became yellow all leaves in AtCKX2 tobacco still remained green. Activities of antioxidant enzymes decreased with leaf age in both tobacco plants except for ascorbate peroxidase (APX) in the old leaves and glutathione reductase (GR) in young leaves. Enhancement of GR activity at all leaf stages, an increase of superoxide dismutase and a decline of catalase in young leaves, as well as an increase of APX in the oldest leaves were observed in AtCKX2 plant compared to control. Similar changes were detected after determination of isoenzymes on zymograms. It is evident that AtCKX2 plants had postponed onset of senescence despite the significantly lowered level of cytokinins. Enhanced antioxidant protection, especially in the oldest leaves, could subsidise this phenomenon.

Effect of water stress and foliar micronutrient application on physiological characteristics and nutrient uptake in sunflower (helianthus annus l.)

Abstract: Babaeian, M., M. Heidari and A. Ghanbari. 2010. Effect of water stress and foliar micronutrient application on physiological caharctersitics and nutrient uptake in sunflower (Helianthus annus L.). Iranian Journal of Crop Sciences. 12 (4) 377-391. (In Persian) To study the effect of foliar micronutrient application under water stress conditions at two stages of growth on chlorophyll fluorescence, chlorophyll, proline and carbohydrates content, nutrient uptake and relation between them with grain yield of sunflower (cv. Alster), a field experimental in split plot design with three replications was conducted at the University of Zabol, in 2007 growing season.. Wter stress at three levels (control, flowering and grain filling stages) were assigned as main plots and seven micronutrient treatments; Fe, Zn, Mn, Fe+Zn, Fe+Mn, Zn+Mn and Fe+Zn+Mn, were randomized in sub-plots. Results showed that water stress at two stages of growth significantly reduced grain yield. The impact of water stress was more pronounced when applied at grain filling and grain yield decreased by about %24.3. Foliar micronutrient application increased grain yield in water stress and application of Mn had the highest positive effect on grain yield. Chlorophyll fluorescence, free proline and total soluble carbohydrates content increased in water stress condition at both stages of growth. The highest concentration of these components were found in the flowering stage. Foliar application of micronutrients increased accumulation of these components, the highest chlorophyll fluorescence was found in Fe, chlorophyll in Fe+Mn, proline in Zn and carbohydrate in Fe+Zn+Mn treatments. In this study, the highest content of Fe and Mn elements were found in non-water stress (control) and the lowest of these elemnets were observed in water stress at the grain filling stage. It can be concluded that water stress at the grain filling stage had the most effect on reducing grain yield of sunflower. Although the highest chlorophyll fluorescence and concentrations of the osmotic regulators (carbohydrates and proline) were found in water stress at the flowering stage. Since water stress at the grain filling stage reduced the uptake of micronutrients, particularly Mn, therefore its effect on sunflower was more pronounced than water stress at the flowering stage.

Plants used by the Mexican

Abstract: The Mexican Kickapoo Indians, today living in a village eighteen miles northwest of Mtizquiz, Coahuila, Mexico, belong to the Central Algonquian group whose language and culture ally them to the Potowatomie, Miami, Illinois, Shawnee, Menomini, and Sank and Fox 3 who probably inhabited the area of the upper Great Lake regions and south to the Ohio River in the early 1600s. 4 In 1645 the French found the Kickapoos living as refugees among the Menomini and Winnebago in Wisconsin, having been driven west by the Iroquois in their quest for furs to trade with the Dutch and English. After meeting the French the Kickapoos began a vigorous fur trade with them, lasting until the latter part of the 18th Century. Their dependence on trade goods caused increased mobility and a marked change in their material culture.5 Until the end of the 18th Century the Central Algonquian tribes, among them the Kickapoos, were strong enough, with the aid of the French, to confine the American settlement to the south of the Ohio River where the Indians waged a constant warfare with the American fortified posts. With the treaty of Greenville in 1795, the Kickapoos, among other tribes, ceded to the United States land in Ohio, Indiana, Illinois, and Michigan in return for an annuity. This act began the removal to the west of the Mississippi for the Kickapoos. 6 Resisting the move was a dissident and conservative group who, rather than con-

Sucrose and Starch Content Negatively Correlates with PSII Maximum Quantum Efficiency in Tomato (Solanum lycopersicum) Exposed to Abnormal Light/Dark Cycles and Continuous Light.

Abstract: Light is most important to plants as it fuels photosynthesis and provides clues about the environment. If provided in unnatural long photoperiods, however, it can be harmful and even lethal. Tomato (Solanum lycopersicum), for example, develops mottled chlorosis and necrosis when exposed to continuous light. Understanding the mechanism of these injuries is valuable, as important pathways regulating photosynthesis, such as circadian, retrograde and light signaling pathways are probably involved. Here, we use non-targeted metabolomics and transcriptomics analysis as well as hypothesis-driven experiments with continuous light-tolerant and -sensitive tomato lines to explore the long-standing proposed role of carbohydrate accumulation in this disorder. Analysis of metabolomics and transcriptomics data reveals a clear effect of continuous light on sugar metabolism and photosynthesis. A strong negative correlation between sucrose and starch content with the severity of continuous light-induced damage quantified as the maximum quantum efficiency of PSII (Fv/Fm) was found across several abnormal light/dark cycles, supporting the hypothesis that carbohydrates play an important role in the continuous light-induced injury. We postulate that the continuous light-induced injury in tomato is caused by down-regulation of photosynthesis, showing characteristics of both cytokinin-regulated senescence and light-modulated retrograde signaling. Molecular mechanisms linking carbohydrate accumulation with down-regulation of carbon-fixing enzymes are discussed.