Selected defoliation studies on butternut Cucurbita moschata, Duchesne cv. Waltham : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science in Plant Physiology at Massey University
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Date
1986
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Massey University
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A field experiment was carried out in the summer 1985/84 at Massey University Campus, Palmerston, New Zealand, to study the effect of selective defoliation on both growth and partitioning of dry matter during reproductive growth in Butternut (Cucurbita moschata, Dunchesne). The plants were trained to grow toward one direction, with one main vine through regular pruning of side branching. Defoliations was carried out at early flowering growth stage, leaving the treated plants with one, two or three block of leaves, at different positions, with different combinations on the stem. Each block has equall number on node, determined at the time of treatment. Newly developed leaves within the defoliated plant section were regularly removed. Results showed that removal of basal leaves block significantly increased the total dry weight and yield by 25% and 30% respectively. This was attributed to the high unit leaf rate and leaf area duration in the later period. Removal of one or more block of leaves from other part of the stem, all reduced plant growth and yield The Butternut plants exhibited a very stable pattern of dry matter partitioning between their organs. The sign of "recovery" which resulted in the proportion of dry matter found in each organs similar to that of CON plants, was observed at the first harvest (7 days) after defoliation. Partitioning of dry matter to fruits was observed to become stronger toward the end of growing period irrespective of pattern of defoliations. The pattern of fruit distributions on the plant was strongly influenced by the position of leaves. At final harvest higher total fruit dry weight and fruit number was found on the stem section with leaves presence. High number of fruit abortions reduced the yield in the stem section without leaves. The overall plant growth was strongly influenced by the age and the total area of leaf present on the plant after defoliation. Plants with more proportion of younger leaves grew better than plants with older leaves.