Physiology of growth and seed production in Lupinus angustifolius L. I. Effects on pod and seed set of controlled short duration high temperatures at flowering

Abstract

Plants of Lupinus angustifolius cv. Unicrop, with branches excised to eliminate competition between branches and the primary inflorescence, were exposed to three temperature treatments: 33/28, 33/13 and 18/28¦C. Each treatment continued for 1, 3 or 5 days, and was begun as flowers were starting to open, or 5 days before, or 10 days after that time. Control plants remained at 18/13¦C throughout. Stress due to high day temperatures before flowering prevented early flowers from developing pods, but later flowers were able to compensate. Temperature stress as flowering began substantially reduced numbers of seed-containing pods, and little compensation was observed, either in later pod set or in seed number per pod. After flowering, high day temperatures did not affect the most developed pods, but ovule abortion reduced seed production in the less developed pods. These findings are discussed in relation to assimilate availability and hormone effects, and the adaptability of the narrow-leafed lupin plant is discussed in view of environmental restraints. Breeding implications are briefly considered.