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  • 1
    Publication Date: 2016-06-02
    Description: Selection and breeding of genotypes with improved drought/heat tolerance become key issues in the course of global change with predicted increased frequency of droughts or heat waves. Several morphological and physiological plant traits must be considered. Rooting depth, root branching, nutrient acquisition, mycorrhization, nodulation in legumes and the release of nutrients, assimilates or phytohormones to the shoot are relevant in root systems. Xylem embolism and its repair after a drought, development of axillary buds and solute channeling via xylem (acropetal) and phloem (basipetal and acropetal) are key processes in the stem. The photosynthetically active biomass depends on leaf expansion and senescence. Cuticle thickness and properties, epicuticular waxes, stomatal regulation including responses to phytohormones, stomatal plugs and mesophyll resistance are involved in optimizing leaf water relations. Aquaporins, dehydrins, enzymes involved in the metabolism of compatible solutes (e.g., proline) and Rubisco activase are examples for proteins involved in heat or drought susceptibility. Assimilate redistribution from leaves to maturing fruits via the phloem influences yield quantity and quality. Proteomic analyses allow a deeper insight into the network of stress responses and may serve as a basis to identify suitable genotypes, although improved stress tolerance will have its price (often lowered productivity under optimal conditions).
    Electronic ISSN: 2077-0472
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by MDPI
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  • 2
    Publication Date: 2018-07-02
    Description: Agriculture, Vol. 8, Pages 97: Plant Nutrient Dynamics in Stressful Environments: Needs Interfere with Burdens Agriculture doi: 10.3390/agriculture8070097 Authors: Urs Feller Stanislav Kopriva Valya Vassileva n/a
    Electronic ISSN: 2077-0472
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by MDPI
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  • 3
    Publication Date: 2015-09-10
    Description: Copper, zinc, manganese, iron, nickel and molybdenum are essential micronutrients for plants. However, when present in excess they may damage the plant or decrease the quality of harvested plant products. Some other heavy metals such as cadmium, lead or mercury are not needed by plants and represent pollutants. The uptake into the roots, the loading into the xylem, the acropetal transport to the shoot with the transpiration stream and the further redistribution in the phloem are crucial for the distribution in aerial plant parts. This review is focused on long-distance transport of heavy metals via xylem and phloem and on interactions between the two transport systems. Phloem transport is the basis for the redistribution within the shoot and for the accumulation in fruits and seeds. Solutes may be transferred from the xylem to the phloem (e.g., in the small bundles in stems of cereals, in minor leaf veins). Nickel is highly phloem-mobile and directed to expanding plant parts. Zinc and to a lesser degree also cadmium are also mobile in the phloem and accumulate in meristems (root tips, shoot apex, axillary buds). Iron and manganese are characterized by poor phloem mobility and are retained in older leaves.
    Electronic ISSN: 2073-4395
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
    Published by MDPI
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  • 4
    Publication Date: 2018
    Description: n/a
    Electronic ISSN: 2077-0472
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by MDPI
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  • 5
    Publication Date: 2023-12-20
    Description: Understanding plant responses to abiotic stresses is central to our ability to predict the impact of global change and environmental pollution on the production of food, feed and forestry. Besides increasing carbon dioxide concentration and rising global temperature, increasingly frequent and severe climatic events (e.g. extended droughts, heat waves, flooding) are expected in the coming decades. Additionally, pollution (e.g. heavy metals, gaseous pollutants such as ozone or sulfur dioxide) is an important factor in many regions, decreasing plant productivity and product quality. This Research topic focuses on stress responses at the level of whole plants, addressing biomass-related processes (development of the root system, root respiration/fermentation, leaf expansion, stomatal regulation, photosynthetic capacity, leaf senescence, yield) and interactions between organs (transport via xylem and phloem, long-distance signaling and secondary metabolites). Comparisons between species and between varieties of the same species are helpful to evaluate the potential for species selection and genetic improvement. This research topic is focused on the following abiotic stresses and interactions between them: - Increased carbon dioxide concentration in ambient air is an important parameter influenced by global change and affects photosynthesis, stomatal regulation, plant growth and finally yield. - Elevated temperature: both the steady rise in average temperature and extreme events of shorter duration (heat waves) must be considered in the context of alterations in carbon balance through increased photorespiration, decreased Rubisco activation and carboxylation efficiency, damage to photosynthetic apparatus, as well as loss of water via transpiration and stomatal sensitivity. - Low temperatures (late frosts, prolonged cold phases, freezing temperature) can decrease overwintering survival rates, productivity of crop plants and species composition in meadows. - Water availability: More frequent, severe and extended drought periods have been predicted by climate change models. The timing and duration of a drought period is crucial to determining plant responses, particularly if the drought event coincides with an increase in temperature. Drought causes stomatal closure, decreasing the cooling potential of transpiration and potentially leading to thermal stress as leaf temperature rises. Waterlogging may become also more relevant during the next decades and is especially important for seedlings and young plants. It is not the presence of water itself that causes the stress, but the exclusion of oxygen from the soil which causes a decrease in respiration and an increase in fermentation rates followed by a period of potential oxidative stress as water recedes. - Salinity: high salt concentration in soil influences soil water potential, the water status of the plant and hence affects productivity. Salt tolerance will become an important trait driven by increased competition for land and the need to exploit marginal lands.
    Keywords: GE1-350 ; QK1-989 ; Q1-390 ; heat ; salt ; Climate Change ; Whole plant physiology ; yield ; Carbon Dioxide ; Low temperature ; water availability ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCN Environmental economics
    Language: English
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  • 6
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    MDPI - Multidisciplinary Digital Publishing Institute
    Publication Date: 2022-01-31
    Description: The papers included in this special issue cover a broad range of aspects ranging from genetics and breeding to crop production in the field. Climate change, intensified agriculture, modifications of land use, or pollution are often accompanied by larger fluctuations including extreme events. The growing world’s population and nutrient deficiencies in agricultural products for human or animal nutrition, or pollutants in harvested products in some regions (quality of yield), are important points to be integrated in a comprehensive analysis aimed at supporting agriculture on the way into a challenging future. It is therefore necessary to develop suitable models to identify potentials and risks. Instabilities (e.g., caused by climatic factors or pests) should be detected as early as possible to initiate corrections in the nutrient supply or in other growth conditions. Sensitive detection systems for nutrient disorders in the field can facilitate this task, and are therefore, highly desirable
    Keywords: GE1-350 ; S1-972 ; Senescence ; Pollution ; Abiotic stress ; Transport via xylem and phloem ; Biotic stress ; Nutrient availability in soil ; Nutrient assimilation ; Nutrient uptake ; Nutrient redistribution ; Nutrient contents in harvested plant products
    Language: English
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 28 (2005), S. 0 
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The impact of heat stress on the functioning of the photosynthetic apparatus was examined in pea (Pisum sativum L.) plants grown at control (25 °C; 25 °C-plants) or moderately elevated temperature (35 °C; 35 °C-plants). In both types of plants net photosynthesis (Pn) decreased with increasing leaf temperature (LT) and was more than 80% reduced at 45 °C as compared to 25 °C. In the 25 °C-plants, LTs higher than 40 °C could result in a complete suppression of Pn. Short-term acclimation to heat stress did not alter the temperature response of Pn. Chlorophyll a fluorescence measurements revealed that photosynthetic electron transport (PET) started to decrease when LT increased above 35 °C and that growth at 35 °C improved the thermal stability of the thylakoid membranes. In the 25 °C-plants, but not in the 35 °C-plants, the maximum quantum yield of the photosystem II primary photochemistry, as judged by measuring the Fv/Fm ratio, decreased significantly at LTs higher than 38 °C. A post-illumination heat-induced reduction of the plastoquinone pool was observed in the 25 °C-plants, but not in the 35 °C-plants. Inhibition of Pn by heat stress correlated with a reduction of the activation state of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). Western-blot analysis of Rubisco activase showed that heat stress resulted in a redistribution of activase polypeptides from the soluble to the insoluble fraction of extracts. Heat-dependent inhibition of Pn and PET could be reduced by increasing the intercellular CO2 concentration, but much more effectively so in the 35 °C-plants than in the 25 °C-plants. The 35 °C-plants recovered more efficiently from heat-dependent inhibition of Pn than the 25 °C-plants. The results show that growth at moderately high temperature hardly diminished inhibition of Pn by heat stress that originated from a reversible heat-dependent reduction of the Rubisco activation state. However, by improving the thermal stability of the thylakoid membranes it allowed the photosynthetic apparatus to preserve its functional potential at high LTs, thus minimizing the after-effects of heat stress.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 102 (1998), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Senescence-associated coordination in amounts of enzymes localized in different cellular compartments were determined in attached leaves of young wheat (Triticum aestivum L. cv. Arina) plants. Senescence was initiated at the time of full leaf elongation based on declines in total RNA and soluble protein. Removal of N from the growth medium just at the time of full leaf elongation enhanced the rate of senescence. Sustained declines in the amount of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco, EC 4.1.1.39), and a marked decrease in the rbcS transcripts, just after full leaf elongation indicated that Rubisco synthesis/degradation was very sensitive to the onset of senescence. Rubisco activase amount also declined during senescence but the proportion of rca transcript relative to the total poly A RNA pool increased 3-fold during senescence. Thus, continued synthesis of activase may be required to maintain functional Rubisco throughout senescence. N stress led to declines in the amount of proteins located in the chloroplast, the peroxisome and the cytosol. Transcripts of the Clp protease subunits also declined in response to N stress, indicating that Clp is not a senescence-specific protease. In contrast to the other proteins, mitochondrial NADH-glutamate dehydrogenase (EC 1.4.1.2) was relatively stable during senescence and was not affected by N stress. During natural senescence with adequate plant nitrate supply the amount of nitrite reductase (EC 1.7.7.1) increased, and those of glutamine synthetase (EC 1.4.7.1) and glutamate synthase (EC 6.3.1.2) were stable. These results indicated that N assimilatory capacity can continue or even increase during senescence if the substrate supply is maintained. Differential stabilities of proteins, even within the same cellular compartment, indicate that proteolytic activity during senescence must be highly regulated.
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  • 9
    ISSN: 1432-2048
    Keywords: Clp (protease) ; Gene expression ; Leaf sen ; escence ; Phaseolus (senescence) ; Stromal enzymes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Our objective was to determine the coordination of transcript and/or protein abundances of stromal enzymes during leaf senescence. First trifolioliate leaves of Phaseolus vulgaris L. plants were sampled beginning at the time of full leaf expansion; at this same time, half of the plants were switched to a nutrient solution lacking N. Total RNA and soluble protein abundances decreased after full leaf expansion whereas chlorophyll abundance remained constant; N stress enhanced the decline in these traits. Abundances of ribulose-1,5-bisposphate carboxylase/oxygenase (Rubisco; EC 4.1.1.39), Rubisco activase and phosphoribulokinase (Ru5P kinase; EC 2.7.1.19) decreased after full leaf expansion in a coordinated manner for both treatments. In contrast, adenosine diphosphate glucose (ADPGlc) pyrophosphorylase (EC 2.7.7.27) abundance was relatively constant during natural senescence but did decline similar to the other enzymes under N stress. Northern analyses indicated that transcript abundances for all enzymes declined markedly on a fresh-weight basis just after full leaf expansion. This rapid decline was particularly strong for the Rubisco small subunit (rbcS) transcript. The decline was enhanced by N stress for rbcS and Rubisco activase (rca), but not for Ru5P kinase (prk) and ADPGlc pyrophosphorylase (agp). Transcripts of the Clp protease subunits clpC and clpP declined in abundance just after full leaf expansion, similar to the other mRNA species. When Northern blots were analyzed using equal RNA loads, rbcS transcripts still declined markedly just after full leaf expansion whereas rca and clpC transcripts increased over time. The results indicated that senescence was initiated near the time of full leaf expansion, was accelerated by N stress, and was characterized by large decline in transcripts of stromal enzymes. The decreased mRNA abundances were in general associated with steadily declining stromal protein abundances, with ADPGlc pyrophosphorylase being the notable exception. Transcript analyses for the Clp subunits supported a recent report (Shanklin et al., 1995, Plant Cell 7: 1713–1722) indicating that the Clp protease subunits were constitutive throughout development and suggested that ClpC and ClpP do not function as a senescence-specific proteolytic system in Phaseolus.
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  • 10
    ISSN: 1432-2048
    Keywords: Key words: Chloroplast ; Nitrogen remobilization ; Pisum ; Proteolysis ; Senescence ; Stromal enzymes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Intact chloroplasts were isolated from mature pea (Pisum sativum L.) leaves in order to study the degradation of several stromal proteins in organello. Changes in the abundances of ribulose-1,5-bisphosphate carboxylase/oxygenase (EC 4.1.1.39), phosphoribulokinase (EC 2.7.1.19), glutamine synthetase (EC 6.3.1.2) and ferredoxin-dependent glutamine:α-ketoglutarate aminotransferase (glutamate synthase; EC 1.4.7.1) were detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by Coomassie-staining of the gels or immunoblotting using specific antibodies for the different enzymes. Degradation of several stromal proteins was strongly stimulated when intact chloroplasts were incubated in the light in the presence of dithiothreitol. Since free radicals may artificially accumulate in the chloroplast under such conditions and interfere with the stability of stromal proteins, the general relevance of these processes remains questionable. In the absence of light, proteolysis proceeded slowly in isolated chloroplasts and was not stimulated by dithiothreitol. Inhibition by ethylenediaminetetraacetic acid (EDTA), 1,10-phenanthroline or excess zinc ions as well as the requirement for divalent cations suggested that a zinc-containing metalloprotease participated in this process. Furthermore, light-independent degradation of ribulose-1,5-bisphosphate carboxylase/oxygenase and phosphoribulokinase was enhanced in chloroplasts isolated from leaves in which senescence was accelerated by nitrogen starvation. Our results indicate that light-independent stromal protein degradation in intact chloroplasts may be analogous to proteolysis that occurs in intact leaves during senescence.
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