SEEDLING WHITE CLOVER RESPONSE TO DEFOLIATION

Defoliation during the early stages of seedling development can influe nce growth of white clover (Trifolium repens L.). Our objective was to determine the response of cultivars with diverse leaf sizes to defoli ation across a range of seedling growth stages. 'Regal' (large-leaf), 'Louisiana S-1' (medium-large-leaf), 'Grasslands Huia' (medium-small-l eaf), and 'Aberystwyth S184' (small-leaf) were grown in the greenhouse and were initially clipped to remove all leaf (except cotyledons) and petiole tissue (1.0-cm stubble) when seedlings attained a unifoliolat e leaf or one, two, four, and eight trifoliolate leaves. Seedlings wer e subsequently clipped in the same manner every 7 or 28 d for the next 28 d. Plant response to defoliation was assessed 7, 14, 21, and 28 d after the last clipping. Seedling shoot dry weight of all cultivars in creased linearly in response to initial leaf stage when subsequent cli pping occurred every 7 d after the initial defoliation. When subsequen t clipping was delayed 28 d, defoliation after the four-trifoliolate s tage did not influence shoot weight of any cultivar except Regal. Desp ite fewer numbers of leaves after regrowth, seedling leaf area of Rega l was always greater than that of the other cultivars. Number of stole n branches of Regal and Louisiana S-1 increased in response to leaf st age at initial defoliation (0.15 branches stage(-1)), while that of Gr asslands Huia and Aberystwyth S184 was relatively unchanged after the four- to six-trifoliolate stage, Permitting white clover seedlings to attain advanced leaf stages before initial defoliation and increasing the time interval before subsequent defoliation will enhance seedling growth and potential survival.