PHENOLOGICAL RESPONSE OF PEA TO WATER-STRESS DURING REPRODUCTIVE DEVELOPMENT

Drought stress affects yield of indeterminate species, but the effects on yield components, seed number, and individual seed weight at harve st are, in some cases, contradictory. The diversity of effects can res ult from the complex sequential development of these plants with respe ct to timing of drought. Two experiments were carried out in a glassho use to study the effect of short-term drought (about 6 d) during diffe rent periods of reproductive development on the phenology of pea (Pisu m sativum L.) cv Solara, and on seed abortion and seed growth rate at each nodal location on the stem. An additional experiment was carried out in the field. Short-term stresses did not change development excep t for the progression of flowering along the stem which was stopped pr ematurely. The duration of the lag-phase between flowering and initiat ion of seed filling, and the duration of seed filling, were not affect ed at any nodal position. Analysis of the distribution of seeds along the stem suggested that the final stage at which seed abortion occurre d corresponded approximately to the initiation of linear seed filling. Seeds that reached this stage before the stress was imposed never abo rted and their growth was maintained. Seed abortion in lag-phase was d ependent on the intensity of drought. If the stress was imposed when a ll the seeds were filling, no abortion occurred and seed growth rates were maintained by mobilization of plant reserves. The results suggest that the plant responded to drought by reducing seed number when poss ible or mobilizing its reserves to maintain a constant seed growth rat e.