Seed Polymorphism and Germination Responses to Salinity Stress in Atriplex triangularis Willd.

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Abstract
Seeds of A. triangularis exhibited a very pronounced morphological and physiological seed polymorphism. Seed size varied from 1.0 to 2.8 mm and predicted the likelihood of successful establishment through its effect on germinatin of seedling vigor. Large seeds had a mean dry weight of 2.44 .+-. 0.16 mg and a mean length of 2.45 .+-. 0.24 mm; medium seeds, mean dry weight of 1.21 .+-. 0.10 mg and mean length of 1.78 .+-. 0.19 mm; small seeds, mean dry weight of 0.64 .+-. 0.04 mg and mean length of 1.27 .+-. 0.10 mm. The degree of salt tolerance increased progressively with increasing seed size. Seeds from all size classes that were initially treated with 2%-5% NaCl had from 85% to 100% germination after being immersed in distilled water for 6 days, indicating a transitory adverse effect of salt stress on germination. The amount of water absorbed by all seeds is influenced by change in media salinity, but not by hormonal treatments. Small seeds contain more Na+ and Cl- than medium and large seeds. Seedling dry weight was related to initial seed size. Salt stress inhibited seedling growth. Gibberellic acid alleviated some of the dormancy in seeds induced by high salt concentrations.