ISHS Acta Horticulturae 504: VI Symposium on Stand Establishment and ISHS Seed Symposium
IMPORTANCE OF SEED CARBOHYDRATES IN RICE SEEDLING ESTABLISHMENT UNDER ANOXIA |
| Authors: | E. S. Ella, T. L. Setter |
| Keywords: | cultivar, endosperm, growth, rice, starch, survival |
| Abstract:
The absence of O2 (anoxia) may reduce energy production for seedling growth during direct seeding in waterlogged soil. Plants under anoxia may produce energy by the alcoholic fermentation pathway (AF). However, this is 18 times less efficient than respiration. A higher carbohydrate substrate supply may help alleviate the adverse effects of reduced energy during anoxia by increasing the rate or duration of AF. The importance of carbohydrates in rice seeds exposed to anoxia was evaluated in two rice cultivars differing in anoxia tolerance. Seed carbohydrate contents were manipulated by (i) grading seeds according to weight and specific gravity, and (ii) removing portions of the endosperm. Anoxia was imposed by germinating seeds in a stagnant deoxygenated agar solution. Starch content was correlated to plant survival in seeds exposed to anoxia with r2=0.73 to 0.88. Glucose feeding during anoxia of half seeds increased survival and plant height and demonstrated that reduced survival was largely the result of low carbohydrate supply and not of seed wounding. The better growth under anoxia in larger seeds, in more dense seeds, and in half seeds supplied with glucose supports the importance of seed carbohydrates in seedling establishment under anoxia. The use of specific gravity as a selection criterion offers a practical method for screening seeds with greater carbohydrate content. Because seed size is usually greater when seeds are grown in areas where there are little or no environmental stresses, the data presented here demonstrate that it is preferable to use heavy and dense seeds grown in a nonstressed environment for planting in environments subject to flooding. | |
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