Influence of seed size on the osmotic adjustment and distributi

INFLUENCE OF SEED SIZE ON THE OSMOTIC ADJUSTMENT AND DISTRIBUTION OF ENERGY IN PARTS OF WINTER WHEAT SEEDLINGS

The aim of this study is drought tolerance of winter wheatseedlings (cv. Regina) under moisture deficit and its dependence on seed reserves altered by abiotic stress. Stress during grain tilling was simulated by defoliation of wheat plants in the field trials. The seeds were sorted according to the seed size. Water stress tolerance of five days old seedlings was measured at moisture deficit. Increase in tolerance to water stress of seedlings was evaluated according to net energy, osmotic potential and dry matter relocation from seeds to etiolated wheat seedlings. The 1000-seed weight does not differ in defoliated and undefoliated plants. There was no difference in net energy of seed at these variants. The difference was only in percentile of individual seed fraction between these variants. The dry weight of 2cm coleptile segments was higher when coteptile had grown from the greater seeds. In contrast, water per dry weight and osmotic potential of this segments was not influenced by seed size. Statistically significant differences in energy was found in the coleptile (15.4 kJ.g dry matter-1) and in the roots (15.5 kJ.g dry matter-1) in contrary to the rest of seed (17.0 kJ.g dry matter-1). Actual osmotic potential of coleptile segments represents osmotic potential at full saturation after normalisation of osmotic potential by van't Hoff law to common water volume. The differences between variants in normalised osmotic potential did not changed and so normalised osmotic potential was taken as a Basic criterion for osmotic adjustment. Seedlings grown from seeds of defoliated plants had lower osmotic adjustment under stress of the tow moister supply. Even when these seedlings grew from the seeds with the same net energy and the same ability to extract dry matter from seeds as control variant. We conclude that the tolerance to water stress in growing seedlings is influenced by the ability of seedlings lower osmotic potential at low moisture availability.

Autor: M. Ottová, F. Hnilička, V. Novák, J. Zámečník

Zdroj: COST 828 Action. Seed Science in the field of genetically controlled stress physiology

(Abstracts), INRA, Toulouse Centre, France, 11 - 14 November, 1998, p. 30, 1998