EFFECT OF SEED MATURITY AND STORABILITY ON VIABILITY AND VIGOUR IN PEA ( Pisum sativum L . ) SEEDS

Storability of seeds is affected by several factors viz., internal (seed moisture contents, stage of seed maturity, composition of seed, physical state of seeds), external factors (temperature, relative humidity and micro flora) and genetic factors. Stage of seed maturity determines the storage potential of seeds if all the factors are kept constant. Although this appears simple principle for individual seeds but a complicated job in plants with indeterminate flowering pattern like pea and is often mismanaged by the growers who use their own saved seeds; a common practice in Pakistan. In such crops, single harvest results in seeds having different degrees of maturity and storage potential. Therefore, an experiment was designed to evaluate the production performance of pea seeds harvested at different stages. Seeds were harvested at two different stages namely mature green stage (fully developed seeds but green in colour) and physiological maturity and stored under room conditions to compare with farmer’s storage environment. Performance was evaluated by conducting emergence test and vigour test at monthly interval to observe the effect of seed maturity on viability and vigour. Time to 50% emergence, mean emergence time, final emergence percentage, vigour index and root and shoot fresh weight was higher for physiologically mature seeds. But dry weight for root and shoot were statistically nonsignificant over the period of study. Results indicate that physiologically mature seed performed better than immature seeds. So spot picking of physiologically mature seed should be done instead of single harvest in peas. INTRODUCTION Pea (Pisum sativum L.), from the family Leguminaseae, is native to Europe and Northern Asia (Warren et al., 1956). It is a self pollinated annual herb, bushy or climbing with weak stem (Duke, 1981). It ranks 4 in the world on production basis (441.53 thousand tonnes) among grain legumes after soya-bean, groundnut and french beans and is grown on an area of 528.71 thousand hectares (FAO, 2005). Although seeds of most species are capable of germination long before physiological maturity (Giri, 1967) but the stage of seed maturity determines the storage potential of seed if all other factors are kept constant (Fontes and Ohlrogge, 1972). Maturity and storability of seed are important but the exact relationship between these variables is not elucidated. Viability