歐洲種及雜交種葡萄對乾旱逆境之光合作用生理反應

Abstract

葡萄(Vitis spp.)為世界重要的園藝作物，主要的栽培種包括歐洲種(V. vinifera)，及其與美洲種(V. labrusca)的雜交種，後者因較適應亞熱帶地區潮濕的氣候，在臺灣廣泛栽培。歐美雜交種葡萄遺傳V. labrusca的特徵，如‘金香’以及‘黑后’葉片背面具有絨毛。絨毛影響葉片的氣體交換，並且被視為忍受乾旱逆境的特徵之一。本文探討‘麗絲玲’(V. vinifera ‘Riesling’) 與雜交種葡萄‘黑后’(‘Black Queen’)和‘金香’(‘Golden Muscat’)氣體交換差異，進一步比較不同程度乾旱逆境下之光合作用特徵，並將數據利用FvCB模型(Farquhar, von Caemmerer, and Berry biochemical model)進行擬合以得到葉肉細胞導度(mesophyll conductance, gm)以及光合生化反應參數。在無水分逆境的環境下，‘麗絲玲’於二氧化碳濃度400 μmol∙mol-1之光合作用淨同化速率(net assimilation rate, A)以及氣孔導度 (stomata conductance, gs)最高。水分利用效率(intrinsic water use efficiency, WUEi)與gm /gs呈現正相關，‘金香’之WUEi與 gm /gs 為三個品種中最高。利用數值積分方法(numerical integrated method)發現飽和光度最大電子傳遞能力(maximum electron transport capacity under saturating light, Jmax)為‘黑后’及‘金香’之A較‘麗絲玲’低的主要因子。為進一步了解gm和WUEi的關係，在不同程度的缺水進行第二個氣體交換測量分析試驗。利用氣孔導度區分不同的缺水程度，結果顯示三葡萄品種之A, Jmax以及初始電子傳遞效率斜率(the initial slope of electron transport rate versus light, φ)皆隨著乾旱程度上升而下降，而WUEi以及gm /gs在乾旱逆境中仍呈現正相關。‘金香’的A受乾旱之影響最小，且在極度乾旱時仍較‘麗絲玲’高。透過數值積分方法分析，擴散性因子(diffusional factors, gs及gm)為兩個雜交種葡萄在乾旱逆境下光合作用效率下降的主要原因，但在‘麗絲玲’中則非主因。但極度乾旱時，gm則是雜交種葡萄維持較‘麗絲玲’高的光合同化效率之主因。觀察葉背絨毛以及氣孔密度，結果顯示‘金香’具有最高的絨毛密度，和WUEi以及耐旱程度一致。本試驗顯示‘黑后’及‘金香’雜交種葡萄不僅具較高絨毛密度，且在缺水逆境下能夠透過維持gm以及WUEi，故較‘麗絲玲’良好的抗乾旱能力。

Grapes (Vitis spp.) are one of the most important horticultural crops worldwide. Commercial cultivars are mainly derived from the European grape, V. vinifera and its hybrids with American grape, V. labrusca. The hybrid grapes are widely cultivated in Taiwan and other subtropical regions, due to their better tolerance to humid climates. The hybrid cultivars ‘Golden Muscat’ and ‘Black Queen’ inherited the leaf abaxial trichomes from V. labrusca. The leaf trichome may affect leaf gas exchange and has been identified as an indicator of drought tolerance. This thesis aimed to reveal the gas exchange differences between ‘Golden Muscat’, ‘Black Queen’ and V. vinifera ‘Riesling’ and their responses to drought. In this study, light response and CO2 response (A-Ci) curves of gas exchange behaviors of potted vinifera ‘Riesling’ and two hybrid cultivars, ‘Black Queen’ and ‘Golden Muscat’ vines were measured at air temperature 25℃. Data were fitted to a modified Farquhar, von Caemmerer, and Berry biochemical model (FvCB) to estimate mesophyll conductance (gm) and biochemical parameters. In the first experiment, gas exchange at ambient CO2 concentration (Ca, 400 μmol∙mol-1) was measured under well-watered condition. The results showed that ‘Riesling’ exhibited the highest net assimilation rate (A) and stomata conductance (gs). Water use efficiency (WUEi) was positive related to gm /gs, which ‘Golden Muscat’ had the highest intrinsic water use efficiency (WUEi) and gm /gs. The data were further analyzed with a numerical integration approach and the result showed that the biochemical factor maximum electron transport capacity under saturating light (Jmax) was the major contributor to the lower A of the hybrid cultivars. In the second experiment, the effect of gm on WUEi, was investigated on vines subject to various drought indicated by gs. The results showed that at ambient CO2 concentration (Ca, 400 μmol∙mol-1), A, Jmax, and the initial slope of electron transport rate versus light (φ) decreased in all three cultivars in vines suffering moderate drought stress. The positive relationship between gm /gs and WUEi was maintained under water deficiency. A of ‘Golden Muscat’ was less influenced by drought stress and superior then that of ‘Riesling’ at extreme water deficiency. the data were further analyzed using a numerically integrated method and the results showed that as the drought stress increased, diffusional factors (gs and gm) were the major contributors to the decrease in A in the two hybrid vines but had little influence in ‘Riesling’ vines. However, in the extreme drought stress, gm was the main positive contributor maintaining a rather stable A of the two hybrids over ‘Riesling’. The trichome densities were positive correlated to WUEi, which ‘Golden Muscat’ was the highest of all. This thesis suggests hybrid cultivars have a better photosynthetic response to extreme water deficiency by maintaining gm and WUEi.