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Water use and carbon budget associated with adaptation and competition of C3 and C4 grasses during drought stress

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Understanding how plants adapt to drought

Scientists in Israel studied the mechanisms that determine drought tolerance in C3 and C4 grasses. Results point towards interesting phenomena which could be exploited in agricultural management.

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Perennial grasses can be classified as either C3 or C4 depending on the pathway they use to capture carbon dioxide (CO2) during photosynthesis. This difference is also associated with different water, light and moisture requirements as well as growth periods. Understanding the mechanisms that allow certain grasses to tolerate low water availability and survive drought conditions was the subject of the EU-funded C3, C4 AND Drought project. Scientists studied the effects of water stress on the photochemical activity of different ecotypes of the same species. To achieve that, they took wild barley from the Negev desert and from a Mediterranean environment. Plants were grown under different irrigation conditions and their photosynthesis rate alongside root and shoot compositions were measured. Desert ecotypes of wild barley decreased their photochemical activity in the leaves under severe drought stress compared to the Mediterranean ecotype, revealing a new adaptation role for photorespiration in desert plant environments. Furthermore, Schismus arabicus was used as a model grass for studying the effect of desiccation on germination and seedling formation. S. arabicus exhibits unique adaptation and survival strategies, which enable it to germinate, develop and produce seeds even in years with extremely low rainfall. Scientists observed that S. arabicus seedling survival depended on the month of germination, proposing the phenomenon of annual periodicity as a survival mechanism. Study findings provided invaluable insight into the mechanisms that allow plant adaptation to long-term drought stress and have important consequences for sustainable agriculture, desertification and C3/C4 competition.

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