Masters Degrees (Soil, Crop and Climate Sciences)
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Browsing Masters Degrees (Soil, Crop and Climate Sciences) by Subject "Amaranths -- Growth"
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Item Open Access Growth and physiological response of amaranth seedlings to temperature and drought stress(University of the Free State, 2013-10) Nuugulu, Leonard Megameno; Pretorius, J. C.; Allemann, J.English: Several environmental factors constantly play a role in crop failures. Of these high temperature and limited water supply are major factors that limit plant productivity and threatens food security. Hence, a search for alternative crops with good tolerance characteristics towards abiotic stress is an ongoing process. Amaranth has been established as an annual vegetable and grain crop and is seen as a prospective alternative crop. Seed germination and seedling development are presumed to be the most critical stages in the life cycle of many seed propagated crops. This served as a rationale for the underlying study on two amaranth species in terms of seed germination, as well as the morphological and physiological response of seedlings to different temperature (25, 30, 35, 40˚C) and water potential (0, -250, -500, -750, -1000, -1250 kPa) regimes. For A. cruentus the optimum temperature was between 25 and 30oC and between 30 and 35oC for A. hybridus in terms of seed germination and early seedling growth. A. hybridus showed a greater level of adaptation to the higher temperature regimes as well as when simultaneously exposed to a rather stringent water potential of -1250 kPa by maintaining root growth better than A. cruentus. Moreover, the imposed temperature/drought stress condition had no significant effect on either of the physiological parameters tested in the former species. These included sugar and total water soluble protein levels as well as photosynthesis and respiratory capacity. Together with the ability of stressed seedlings to maintain growth, the latter strongly suggests that the metabolic events were scarcely affected in A. hybridus, supporting the postulate that it showed a higher degree of tolerance towards abiotic stress conditions. Alternatively, more than half of these events were found to be upgraded in A. cruentus seedlings and interpreted as an attempt by this species to counteract the stress effects, but not successfully, as measured by its inability to maintain seedling growth under these stress conditions.