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Abiotic stress is the negative impact of non-living factors on the living organisms in a specific environment. The non-living variable must influence the environment beyond its normal range of variation to adversely affect the population performance or individual physiology of the organism in a significant way.
Vascular plants, or collectively the phylum Tracheophyta, form a large group of land plants that have lignified tissues for conducting water and minerals throughout the plant. They also have a specialized non-lignified tissue to conduct products of photosynthesis. Vascular plants include the clubmosses, horsetails, ferns, gymnosperms, and angiosperms. Scientific names for the group include Tracheophyta, Tracheobionta and Equisetopsida sensu lato. Some early land plants had less developed vascular tissue; the term eutracheophyte has been used for all other vascular plants, including all living ones.
In botany, a stoma, also called a stomate, is a pore found in the epidermis of leaves, stems, and other organs, that controls the rate of gas exchange between the internal air spaces of the leaf and the atmosphere. The pore is bordered by a pair of specialized parenchyma cells known as guard cells that regulate the size of the stomatal opening.
C4 carbon fixation or the Hatch–Slack pathway is one of three known photosynthetic processes of carbon fixation in plants. It owes the names to the 1960s discovery by Marshall Davidson Hatch and Charles Roger Slack.
C3 carbon fixation is the most common of three metabolic pathways for carbon fixation in photosynthesis, the other two being C4 and CAM. This process converts carbon dioxide and ribulose bisphosphate (RuBP, a 5-carbon sugar) into two molecules of 3-phosphoglycerate through the following reaction:
Nitrogen assimilation is the formation of organic nitrogen compounds like amino acids from inorganic nitrogen compounds present in the environment. Organisms like plants, fungi and certain bacteria that can fix nitrogen gas (N2) depend on the ability to assimilate nitrate or ammonia for their needs. Other organisms, like animals, depend entirely on organic nitrogen from their food.
Moisture stress is a form of abiotic stress that occurs when the moisture of plant tissues is reduced to suboptimal levels. Water stress occurs in response to atmospheric and soil water availability when the transpiration rate exceeds the rate of water uptake by the roots and cells lose turgor pressure. Moisture stress is described by two main metrics, water potential and water content.
Ecophysiology, environmental physiology or physiological ecology is a biological discipline that studies the response of an organism's physiology to environmental conditions. It is closely related to comparative physiology and evolutionary physiology. Ernst Haeckel's coinage bionomy is sometimes employed as a synonym.
Howard Griffiths is a physiological ecologist. He is Professor of Plant Ecology in the Department of Plant Sciences at the University of Cambridge, and a Fellow of Clare College, Cambridge. He formerly worked for the University of Dundee in the Department of Biological Sciences. He applies molecular biology techniques and physiology to investigate the regulation of photosynthesis and plant water-use efficiency.
In botany, drought tolerance is the ability by which a plant maintains its biomass production during arid or drought conditions. Some plants are naturally adapted to dry conditions, surviving with protection mechanisms such as desiccation tolerance, detoxification, or repair of xylem embolism. Other plants, specifically crops like corn, wheat, and rice, have become increasingly tolerant to drought with new varieties created via genetic engineering. From an evolutionary perspective, the type of mycorrhizal associations formed in the roots of plants can determine how fast plants can adapt to drought.
A xerophyte is a species of plant that has adaptations to survive in an environment with little liquid water. Examples of xerophytes include cacti, pineapple and some gymnosperm plants. The morphology and physiology of xerophytes are adapted to conserve water during dry periods. Some species called resurrection plants can survive long periods of extreme dryness or desiccation of their tissues, during which their metabolic activity may effectively shut down. Plants with such morphological and physiological adaptations are said to be xeromorphic. Xerophytes such as cacti are capable of withstanding extended periods of dry conditions as they have deep-spreading roots and capacity to store water. Their waxy, thorny leaves prevent loss of moisture.
Transpiration is the process of water movement through a plant and its evaporation from aerial parts, such as leaves, stems and flowers. It is a passive process that requires no energy expense by the plant. Transpiration also cools plants, changes osmotic pressure of cells, and enables mass flow of mineral nutrients. When water uptake by the roots is less than the water lost to the atmosphere by evaporation plants close small pores called stomata to decrease water loss, which slows down nutrient uptake and decreases CO2 absorption from the atmosphere limiting metabolic processes, photosynthesis, and growth.
Hydraulic redistribution is a passive mechanism where water is transported from moist to dry soils via subterranean networks. It occurs in vascular plants that commonly have roots in both wet and dry soils, especially plants with both taproots that grow vertically down to the water table, and lateral roots that sit close to the surface. In the late 1980s, there was a movement to understand the full extent of these subterranean networks. Since then it was found that vascular plants are assisted by fungal networks which grow on the root system to promote water redistribution.
Specific leaf area (SLA) is the ratio of leaf area to leaf dry mass. The inverse of SLA is Leaf Mass per Area (LMA).
Deficit irrigation (DI) is a watering strategy that can be applied by different types of irrigation application methods. The correct application of DI requires thorough understanding of the yield response to water and of the economic impact of reductions in harvest. In regions where water resources are restrictive it can be more profitable for a farmer to maximize crop water productivity instead of maximizing the harvest per unit land. The saved water can be used for other purposes or to irrigate extra units of land. DI is sometimes referred to as incomplete supplemental irrigation or regulated DI.
Photosynthesis systems are electronic scientific instruments designed for non-destructive measurement of photosynthetic rates in the field. Photosynthesis systems are commonly used in agronomic and environmental research, as well as studies of the global carbon cycle.
Breeding for drought resistance is the process of breeding plants with the goal of reducing the impact of dehydration on plant growth.
Biomass partitioning is the process by which plants divide their energy among their leaves, stems, roots, and reproductive parts. These four main components of the plant have important morphological roles: leaves take in CO2 and energy from the sun to create carbon compounds, stems grow above competitors to reach sunlight, roots absorb water and mineral nutrients from the soil while anchoring the plant, and reproductive parts facilitate the continuation of species. Plants partition biomass in response to limits or excesses in resources like sunlight, carbon dioxide, mineral nutrients, and water and growth is regulated by a constant balance between the partitioning of biomass between plant parts. An equilibrium between root and shoot growth occurs because roots need carbon compounds from photosynthesis in the shoot and shoots need nitrogen absorbed from the soil by roots. Allocation of biomass is put towards the limit to growth; a limit below ground will focus biomass to the roots and a limit above ground will favor more growth in the shoot.
Plant growth analysis refers to a set of concepts and equations by which changes in size of plants over time can be summarised and dissected in component variables. It is often applied in the analysis of growth of individual plants, but can also be used in a situation where crop growth is followed over time.
Barley is known to be more environmentally-tolerant than other cereal crops, in terms of soil pH, mineral nutrient availability, and water availability. Because of this, much research is being done on barley plants in order to determine whether or not there is a genetic basis for this environmental hardiness.
References
- ↑ Farquhar, G.D.; Rashke, K. (1978). "On the resistance to transpiration of the sites of evaporation within the leaf". Plant Physiology. 61: 1000–1005. doi:10.1104/pp.61.6.1000.
- ↑ Meinzer, F. C., Ingamells, J. L., Crisosto, C. (1991). "Carbon Isotope Discrimination correlates with bean yield of diverse coffee seedling populations". HortScience. 26 (11): 1413–1414.
- 1 2 Maximov, N. A. (1929). The plant in relation to water. George Allen & Unwin LTD London.
- ↑ Tallec, T.; Béziat, P.; Jarosz, N.; Rivalland, V.; Ceschia, E. (2013). "Crops' water use efficiencies in temperate climate: Comparison of stand, ecosystem and agronomical approaches". Agricultural and Forest Meteorology. 168: 69–81. doi:10.1016/j.agrformet.2012.07.008.
- ↑ Vadez, V.; Kholova, J.; Medina, S.; Kakkera, A.; Anderberg, H. (2014). "Transpiration efficiency: new insights into an old story". Journal of Experimental Botany. 65 (21): 6141–6153. doi:10.1093/jxb/eru040.
- ↑ Ehleringer, J. R. (1993). "Variation in Leaf Carbon-Isotope Discrimination in Encelia farinosa : Implications for Growth Competition and Drought Survival". Oecologia. 95: 340–346. doi:10.1007/BF00320986. ISSN 0029-8549.
- ↑ Kenney, A. M., McKay, J. K., Richards, J. H., Juenger, T. E. (2014). "Direct and indirect selection on flowering time, water-use efficiency (WUE, δ13C), and WUE plasticity to drought in Arabidopsis thaliana". Ecology and Evolution. 4 (23): 4505–4521. doi:10.1002/ece3.1270. ISSN 2045-7758.
- ↑ Campitelli, B. E., Des Marais, D. L., Juenger, T. E. (February 2016). "Ecological interactions and the fitness effect of water-use efficiency: Competition and drought alter the impact of natural MPK12 alleles in Arabidopsis". Ecology Letters. 19 (4): 424–434. doi:10.1111/ele.12575. ISSN 1461-023X.
- ↑ Condon, A. G., Richards, R. A., Rebetzke, G. J., Farquhar, G. D. (2004). "Breeding for high water-use efficiency". Journal of Experimental Botany. 55: 2447–2460. doi:10.1093/jxb/erh277. ISSN 0022-0957.
- ↑ Bacon, M. Water Use Efficiency in Plant Biology. Oxford: Blackwell Publishing Ltd., 2004. ISBN 1-4051-1434-7. Print.
- ↑ Blum, A. (2009). "Effective use of water (EUW) and not water-use efficiency (WUE) is the target of crop yield improvement under drought stress". Field Crops Research. 112: 119–123. doi:10.1016/j.fcr.2009.03.009.
- ↑ Iljin, V. (1916). "Relation of transpiration to assimilation in steppe plants". Journal of Ecology. 4: 65–82. doi:10.2307/2255326.
- ↑ Bates, C.G. (1923). "Physiological requirements of Rocky Mountain trees". Journal of Agricultural Research. 24: 97–164.
- ↑ Linares, J. C.; Camarero, J.J. (2012). "From pattern to process: linking intrinsic water-use efficiency to drought-induced forest decline". Global Change Biology. 18: 1000–1015. doi:10.1111/j.1365-2486.2011.02566.x.
