Abstract/Summary

High temperature and drought, together or alone, reduce rice (Oryza sativa L.) crop yield. Their effect at different periods during seed development and maturation on rice seed quality, and its development, was investigated with pot-grown plants in controlled-environment growth cabs (28/20°C,11h/13h) or glass-houses (28/20℃, 12h/12h). Ending irrigation early in japonica rice cv. Gleva at early- to mid-seed filling (7 or 14 days after anthesis, DAA) resulted in earlier plant senescence, more rapid decline in seed moisture content and initially more rapid seed quality development, but subsequently substantial decline in planta in ability to germinate normally. Subsequent seed storage longevity at 40℃ with c. 15% moisture content was ultimately greatest in the control (no drought); both drought treatments declined in subsequent longevity in planta from 16 or 22 DAA onwards, respectively. A similar investigation but with drought applied later (14 or 28 DAA) also showed poorer seed longevity in drought treatments at harvest maturity (42 DAA). In both investigations, the earlier the drought the greater the damage to subsequent seed quality. Well-irrigated plants exposed to 40/30℃ for 3 days provided poorer subsequent seed quality (shorter longevity) the earlier during development they received high temperature (HT) treatment. The effect was greatest with HT at around anthesis and histodifferentiation, with no effect of HT during the seed maturation phase. Damage to seed quality from combining both stresses (drought, HT) was greater than each alone; indica rice cv. Aeron 1 was affected less by these stresses than japonica cv. Gleva. It is concluded that drought, as well as HT, damages subsequent seed quality in rice, the period around anthesis is the most vulnerable stage of plant development for such damage to seed, and seed quality in japonica rices is more vulnerable than in indica rices to stress in the production environment