engleski

Photosynthetically active radiation in Istrian Malvasia fruit zone as affected by early leaf removal

The aim of this study was to investigate the impact of early leaf removal on the intensity of photosynthetically active radiation (PAR) in the fruit zone of Istrian Malvasia (Vitis vinifera L.) vines. Leaf removal of eight basal leaves per shoot was performed either pre-bloom (PB) or at berry set (BS) on vertically shoot positioned Istrian Malvasia vines. Control treatment without leaf removal was also included. Fixed radiation sensors were used to intercept PAR in the fruit zone of each treatment and another sensor was allocated above the top of the canopy in order to measure total incident radiation. PAR measurement started when berries were pea size and lasted until harvest. BS treatment had the highest intensity of PAR inside the fruit zone throughout the measured period, while control treatment vines had the lowest intensity due to higher shading of leaves from the primary shoots. PB treatment had higher intensity of PAR than control treatment, although considerably lower than BS treatment. The differences among BS and other two treatments were largest in the first two weeks of PAR measurement. Higher intensity of PAR in BS treatment in comparison to PB treatment is a consequence of later and less intensive lateral regrowth in BS treatment. As PAR affects carbon assimilation of leaves and total dry matter production, the results of this study affirm the positive effects of early leaf removal in the production of Istrian Malvasia grapes and indicate that this practice is suitable to avoid the formation of shaded canopies which are usual for this cultivar.

photosynthetically active radiation; early leaf removal; Istrian Malvasia

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