The Development of Desiccation-tolerance and Maximum Seed Quality During Seed Maturation in Six Grain Legumes

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Abstract
‘Physiological maturity’, i.e. the time when seeds reach their maximum dry weight during development, occurred when maturation drying on the parent plant in the field had reduced seed moisture content to approximately 60 per cent in faba bean (Vicia faba L.), lentil (Lens culinaris Medic.), chickpea (Cicer arietinum L.), white lupin (Lupinus albus L.), soya bean (Glycine max [L.] Merr.) and pea (Pisum sativum L.) The onset of desiccation-tolerance, i.e. the ability of seeds to germinate following harvest and rapid artificial drying, coincided with physiological maturity, except in pea where it occurred a little earlier at about 70 per cent moisture content. Maximum seed quality as determined by maximum viability, minimum seedling abnormalities and maximum seedling size occurred in pea, chickpea and lupin when seeds were harvested for rapid drying at physiological maturity; but for maximum seed quality in the other species maturation drying had to proceed further - to about 45 per cent moisture content in soya bean and to about 30 per cent moisture content in lentil and faba bean seed crops. Much of this variation amongst the six species, however, was due to differences in the variation in maturity within each seed crop. Results for individual pods showed that peak maturity, i.e. maximum seed quality following harvest and rapid artificial drying, was achieved in all six species once maturation drying had reduced the moisture content of the seeds to 45–50 per cent. In pea, faba bean and soya bean there was a substantial decline in viability and an increase in seedling abnormalities when harvest was delayed beyond the optimal moisture content for harvest.