Correlative effects of leaf age on reproductive growth in red clover (Trifolium pratense L.)

The contribution of individual leaves towards the flowering response in red clover (Trifolium pratense L.) seedlings at the three-leaf stage is described. Removal of the first (oldest) or first and second leaves resulted in large increases (up to 300%) in both the rate of stem extension and the degree of apical differentiation.Removal of the youngest leaves depressed both processes. Application of cycloheximide to specific leaves produced effects similar to defoliation, but chloramphenicol was generally inhibitory and kinetin substantially ineffective. Translocation patterns between leaves and the shoot apex were studied using [(14)C] sucrose and [(3)H] gibberellin A1. There was appreciable movement between leaves, but exposure to long-days depressed the transport of labelled assimilate. Label arriving at the apex was increasingly derived from the younger leaves as floral induction proceeded.