Correlation of growth of the root and shoot systems of white clover after a period of water shortage and/or defoliation

Abstract

Relationships were established between growth in root and shoot systems of white clover under conditions of stress such as soil water deficit and defoliation that typically occur in the field. Vegetative clones of white clover (Trifolium repens cv. Haifa) were grown in pots in a greenhouse for 6 weeks. The growth and development of the shoot and root systems were followed by destructive harvests at the outset and after 2, 3, 4, 5 and 6 weeks. Treatments comprised: A) plants well watered with nutrient solution; B) restricted watering; C) well watered but defoliated after harvest three and allowed to regrow and D) restricted watering and defoliated. At the outset, all plants were of similar size (< 1.0 g DM), but by the end of the experiment, plant size ranged from 23.0 g DM in treatment A to 3.1 g DM in D. For plants in the ideal treatment (A), there were strong linear correlations between the measured root and shoot parameters that were evident at all harvests. For plants growing in the stress treatments (B-D), these correlations were initially disrupted but were almost fully restored by the end of the experiment. In white clover, the growth and morphological development of roots and shoots are highly correlated. If this balance is disturbed, white clover responds to rapidly re-establish the original coordination. If these same relationships exist in field soils, then higher shoot yields will only be possible if the growth of more roots is encouraged.