Influence of Water Stress on Flowering and Seed Production of Macroptilium atropurpureum cv. Siratro

Macroptilium atropurpureum cv. Siratro was grown in large soilbeds with a constant water table below, developing a dawn leafwatêr potential of --0.25 MPa. Water stresses equivalentto -0.7 or -1.0 MPa were developed over 14 d, causing reducedstem and bud elongation, leaf expansion, and bud differentiationand survival. Apex size, the proportion of buds which were floralor vegetative, the early phases of floral initiation, and seedformation on advanced inflorescences were little affected duringthe water deficit period. Upon rewatering previously stressed plants showed increasesrelative to control plants in the rates of shoot appearance,leaf expansion and new node appearance. The ratio of buds becomingfloral was independent of watering treatment, and the enhancedrate of floral bud production in the previously-stressed treatmentswas due to higher rates of total bud differentiation which persistedfor up to six weeks after rewatering. Survival of floral budswas reduced by previous stress, but number of flowers per inflorescence,pod setting, seed number per pod and 100-seed weight were independentof treatment. Seed production was controlled by inflorescencedensity. Rate of seed production was independent of treatmentduring water deficit and four weeks subsequently, and was thenenhanced by 46 and 54 per cent relative to the control in the–0.7 and –1.0 MPa treatments respectively. Macroptilium atropurpureum, Siratro, floral initiation, flowering, seed production, water stress, bud development