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Heat acclimation of grapevine leaf photosynthesis: mezo- and macroclimatic aspects

Zsófi, Zsolt, Váradi, Gyula, Bálo, Borbála, Marschall, Marianna, Nagy, Zoltán, Dulai, Sándor
Functional plant biology 2009 v.36 no.4 pp. 310-322
thermal stability, grapes, acclimation, drought, light intensity, fluorescence, heat stress, water stress, zeaxanthin, Vitis vinifera, photosynthesis, leaves, air temperature, antheraxanthin, leaf water potential, climatic factors, plant available water, biochemical pathways, violaxanthin
Heat sensitivity of grapevine (Vitis vinifera L. cv. Kékfrankos) photosynthesis was studied in two vineyards (Eger-Kőlyuktető, flat; and Eger-Nagyeged hill, steep slope) with different mesoclimates and water supply conditions in two climatically different years. 2007 was drier and warmer, with higher vapour pressure deficit (VPD) than 2005. Pre-dawn water potential measurements indicated mild water deficit at the steep-sloped vineyard. In July 2005 mild water deficit enhanced the thermostability of grapevine photosynthesis, as reflected in the temperature dependence of optimal quantum yield (Fv/Fm) and in the critical temperature of initial fluorescence (F₀Tc). Decreased Fv/Fm and actual quantum yield (ΔF/Fm') was recorded at most temperatures in September at the water-stressed (steep slope) site. This time, F₀Tcs were also lower due to early leaf senescence. In September 2007, heat sensitivity of Fv/Fm was similar to 2005, and ΔF/Fm' indicated higher thermostability at both sites, but keeping the consistent difference between the two vineyards. The critical points of steady-state fluorescence (FsTc) were higher by 3-6°C at both vineyards in 2007 than in 2005. Although, in September thermolabile F₀ signals were measured at the water-stressed vineyard, the heat sensitivity was not decreased in light adapted state, assumingly as a result of enhanced xanthophyll cycle pigment pool size. The higher xanthophyll pigments pool size (V+A+Z) in 2007 (compared to 2005) at the unstressed (flat) vineyard suggests that high temperature and VPD play a role in changing (V+A+Z)/(chl a+b), and, thus, results in higher thermostability under high light conditions.