Grapevine photosynthesis: effects linked to light radiation and leaf age.

This paper highlights the basic knowledge and the latest achievements in regard to the relationship between net photosynthesis (Pn), radiation, and leaf age in the grapevine. Variation of photosynthesis versus the above factors is discussed at both the single leaf and the whole canopy levels and practical guidelines for improved canopy management are inferred as well. The effects of radiation on leaf net photosynthesis are examined in terms of light saturation curves, type of light regime (continuous versus intermittent lighting) and light exposure during and after leaf development. Scaling up of Pn/radiation relationship to the whole canopy level is also tackled and methods to assess performance of trellises varying in form and type of pruning with respect to light use and distribution are discussed. Variation of Pn as related to leaf age is treated as both seasonal trends and modifications depending upon leaf position along the stem. Factors involved in the grapevine leaf senescence pattern are presented and sensitivity of the leaf aging process as related to environmental conditions (i.e. radiation) and cultural factors (i.e. winter or summer pruning techniques) is analyzed. Seasonal modification of whole canopy photosynthesis is also reported to suggest that maximum Pn is reached around veraison. Basic information reported on the Pn/leaf-canopy age patterns is also highlighted to be of valuable use as a guide for operations which typically alter the leaf demography in a canopy (i.e. shoot removal and trimming, defoliation).