Problems with Regard to the Loss of Seed Viability of Shorea robusta Gaertn. F.

Shorea robusta Gaertn. f. (Sal) seeds remain viable only for 10-days from the date of harvest under natural conditions. The non-viability is due to loss of moisture from the seed coat followed by cotyledon and embryo. Hairs present in the viable seed coat are lost in the non-viable ones. It is possible to store the seeds in, viable condition for two months after harvest at a temperature between l0-12°C. The seeds have been classified into four categoris on the basis of morphological characters. Absorption of water during germination is an important marker in identifying the seed viahility. Gibberellic acids (GA₁, GA₃, GA₅,. GA₁₃,) and indole acetic acid (IAA) in both free and conjugated forms which are present in viable seeds disappear in non-viable ones. The carbohydrates, proteins and acid phosphates which are also present in the viable seeds decline in the non-viable ones along with the denaturation of proteins In the non-viable seeds phenolics as well as fatty acids are formed which act as inhibitors of germination. The loss of moisture from the seed coat causes the loss of membrane integrity and this can be overcome by storing the seeds at cool temperature (10-12°C). Kinetin (0.01 mg/1 treatment is also effective.