Drought resistance in rubber tree. II. Growth and assimilation partitioning of six clones subjected to water deficit

Abstract

Plants from IAN 717, IAN 873, IAN 2903, IAN 3087, IAN 6323 and Fx 3899 rubber tree (Hevea spp.) clones grown in a greenhouse were subjected to cycles of water deficit with the objective of evaluating the effects on growth and assimilation partitioning. After 185 days and five cycles of stress, a reduction in the number of leaves, in the number of flushes, and in the length and diameter of the shoots occurred in the majority of the clones. The IAN 2903 progeny showed an increase in the number of leaves (4.7%) and in the number of flushes (10%). Shoots of the IAN 717 and IAN 3087 progenies were the least affected in their growth. The assimilation partitioning showed a modification in relation to the sinks occurring with the deficit; the prefered sinks were the root in the Fx 3899 and 873 progenies the stem in the IAN 3087 and IAN 6323 progenies and the leaf in the IAN 717 and IAN 2903 progenies. The ratio of the aerial part to the root system was greater in the IAN 2903 progeny and smaller in the Fx 3899 progeny. Under water stress no significant changes occurred in the specific leaf area production values for leaf area and in the leaf area ratio, but the net assimilation value and the accumulation and production of dry matter decreased differentially when submitted to water deficit. The clone least affected by the stress was IAN 3087. The greatest reductions on studied parameters occurred in Fx 3899. The results observed in each clone were discussed in relation to each parameter studied.