ISHS Acta Horticulturae 206: Symposium on Grapevine Canopy and Vigor Management, XXII IHC
INFLUENCE OF LIGHT ON COMPOSITION AND QUALITY OF GRAPES |
| Author: | R. E. Smart |
| Abstract:
Sunlight can affect fruit composition through photosynthetic, thermal or phytochrome effects, all involving different wavebands of radiation. Grapevines are able to differentiate between overcast and plant shade through the 660 nm/730 nm (Red:Far Red or R:FR) ratio, which has ambient values of about 1.1 and falls to 0.1 or less inside canopies. Canopy and shoot spacing effects on the R:FR ratio of leaves are shown, leading to principles of canopy design to maintain high levels of the ratio. The effect of low light levels on fruit composition are reviewed, and the difficulties of experimentation in this area highlighted. Changes in fruit composition due to shade can be associated with known effects of phytochrome on enzyme activity, and further research in the regulatory role of phytochrome is urged. | |
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