Plastic covering film can reduce midday depression photosynthesis of field-grown tropical grapevine in high photosynthetic photon flux
2017
Almeida, L. V. B de | Figueiredo, F. A. M. M. A. | Deus, B. C de | Viana, L. H. | Ferraz, T. M. | Martins, A. O. | Smith, R. E. B. | Campostrini, E.
In tropical regions, farmers have used transparent plastic covering (TPC) above the canopy of grapevines cultivated under field conditions, in order to avoid wetting the leaves and fruits, and reduce the use of fungicides. In these regions, it was found that the TPC reduced the photosynthetic photon flux (PPF) on the canopy, and increased the fraction of diffuse radiation. In addition, the wind speed is reduced below the canopy, and there is a leaf-to-air vapour pressure difference. Still, in these tropical regions, little information related to the effects of TPC on photosynthetic performance and growth is available. The objective of this study was to understand the effects of TPC on gas exchange, photochemical efficiency, and growth in two grapevine genotypes, 'Niagara Rosada' and 'Clara', in the northern of Rio de Janeiro state (21°30'S, 41°42'W). The results showed that the growth of 'Niagara Rosada', assessed by the inter-node diameter and the branch length, was affected in plants grown without the TPC. The TPC resulted in higher leaf diameter and longer length of the branches in 'Clara'. In both cultivars, the effect of TPC on midday photosynthesis, stomatal conductance and transpiration was largest on overcast days. However, on clear days, the TPC reduced the negative effects of excessive light energy on gas exchange in both cultivars, and without the use of TPC, the gas exchange of 'Niagara' was the most affected. In the tropics at high PPF, the use of TPC may contribute to a reduction in midday depression photosynthesis caused by stomatal limitations.
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