Morphological Variation between Seedling Progenies of Viminaria juncea (Schrad. & Wendl.) Hoffmans. (Fabaceae) and its Physiological Significance

Abstract

Seed of Viminaria juncea was collected from single plants in a range of habitats throughout SW. Australia and the resulting seedling progenies grown in sand culture in a glasshouse. Each set of seedlings displayed highly uniform shoot morphology regardless of growth conditions, but differed markedly from other progenies in branching habit and timing of the transition from juvenile spathulate and trifoliolate leaves to adult phyllodineous foliage. Root flooding inhibited growth of progenies of squat phyllodineous habit more than tall leafy types. Seedling growth responded linearly to increased phosphate supply (0.6-16.0 mg P/I). Percentage plant dry weight as nodules increased 2-3-fold with increasing phosphate but proportional mass as cluster (proteoid) roots declined sharply. Statistically significant differences between progenies in nodulation and cluster root production were evident in certain phosphate treatments. Extreme early phyllodineous and prolonged leafy morphotypes were selected from a mixed population of seedlings (parent seed pooled from 70 habitats) and their growth and water use recorded under continuous root flooding, mesic, or drought-simulating conditions. Leafy morphotypes outgrew phyllodineous counterparts in flooded or mesic conditions, but shed their leaflets when droughted and thereafter behaved as phyllodineous morphotypes. Water-use efficiencies were similar between morphotypes and treatments (range 2.58-2.74 g dry matter gain/l water used), except for flooded phyllodineous seedlings for which 2.16 g/l was recorded. The genecological significance of the data is discussed.