Leaf development in swards of white clover ( <i>Trifolium repens</i> L.)

Abstract

Summary An experiment is described in which the influence of development and senescence of leaves that were initiated at different stages of re‐growth, on the Leaf Area Index (L.A.I.) of white clover swards, was determined. The total L.A.I, of the swards reached a ceiling value of 5.5 twenty days from defoliation, and thereafter until the end of the experiment only small changes occurred. Of this leaf, 3–3.5 units were fully opened, actively photo‐synthesising leaves, and 0.5 units were bud leaves. The remainder were either axillary leaf (0.5 units), or leaf in various stages of senescence (1—1.5 units). The pattern of sward development was markedly influenced by petiole and lamina development of individual leaves initiated at different stages of growth. The laminae of leaves initiated after the ceiling L.A.I, was attained were twice the size of the first‐formed leaves, and petiole dimensions were 2.5 and 4 times the length and weight respectively. The dimensions of leaves marked on intermediate dates increased progressively to these maximum values. This pattern of leaf and sward growth is discussed in relation to the light requirements of developing leaves. The significance of leaf death on the turnover of symbiotically fixed nitrogen is also discussed.