Photoprotective Function Of Photorespiration In Grapevine Under Drought Stress

Seven grapevine cultivars originated from different regions, i.e. 'Carbernet Sauvignon'and 'Queen of Vineyard' (two members of the Western Europe Cultivars Group), 'Rizamat'(a member of the East Cultivars Group), 'Red Double Taste' (a hybridized cultivar from Vitisvinifera L. and V. labrusca L.), '1103Paulsen' (a hybridized rootstock), 'Red Globe' and'Autumn Royal' (two new hybridized cultivars between cultivars groups which were warmlyplanted in recent years) were selected. After different drought stress, a combinedmeasurement of gas exchange and chlorophyll fluorescence was conducted to evaluate theeffects of drought stress to photoinhibition, as well as the role of photorespiration andxanthophyll cycle in photoprotective mechanism. After photorespiration and xanthophyllcycle were separately inhibited, the complementary effect of these two photoprotectivepathways was discussed. Detached leaves of different grapevine cultivars, i.e. 'CabernetSauvignon', 'Cabernet Franc', 'Merlot', and a rootstock, '1103Paulsen' were selected asmaterials, and photoinhibition degree, photorespiration activity as well as its photoprotectivefunction under drought stress were studied. The results are as follows: 1.Under the same drought stress treatment, different photoinhibition degrees formed indifferent grapevine cultivars. The photoinhibition degree of certain cultivar closely connectedwith its ecological origin. Because of their long-term acclimation to environments, cultivarsoriginating in arid region held high resistance to photoinhibition under drought stressconditions, and acted as an important character of drought resistant abilities. As to 'CabernetSauvignon' and 'Queen of Vineyard', which belong to the 'West Europe Cultivars Group', noobvious decline of Fv/Fm was found in their potted plants even under severe drought stress.Their photosynthetic abilities also greatly recovered after rewatering, i.e. no seriousphotodamage was formed in these cultivars under drought stress. Between them, the ΦPSII of'Queen of Vineyard' under severe drought stress was much lower than that of 'CabernetSauvignon', which suggested that the light use efficiency of the former was much lower thanthe latter under severe drought stress. The potted plants of 'Autumn Royal' and 'Rizamat' 3干旱胁迫下光呼吸在葡萄光保护中的作用sustained high Fv/Fm and ΦPSII before moderate drought stress, but seriously declined undersevere drought stress, which indicated that these cultivars had a weak resistant ability toextreme drought stress. A hybridized cultivar of Vitis vinifera L. and V. labrusca L., 'RedDouble Taste', its Fv/Fm and ΦPSII expressed mild decline along drought stress grade. ΦPSIIof 'Red Double Taste' was the highest among seven cultivars under severe drought stresscondition, which might closely connected with its high photorespiration activity. Another newcultivar, 'Red Globe', and a rootstock, '1103Paulsen', the Fv/Fm and ΦPSII of their pottedplants declined markedly under slight drought stress, which suggested that they held a weakability to defend against photoinhibition. 2.As the competitive inhibition reaction of carbon assimilation, photorespiration ingrapevine acts an important role in photoprotective mechanism under drought stressconditions. There were obvious distinctions about the photoprotective function ofphotorespiration among different cultivars. Photorespiration of 'Red Double Taste' and'Cabernet Sauvignon' played an important role in photoprotection under severe drought stresscondition, than of 'Rizamat', 'Queen of Vineyard' and 'Autumn Royal' only worked beforemoderate drought stress, and also was an important factor to sustain a relatively high ΦPSII.Photorespiration of 'Red Globe' and '1103Paulsen' decreased obviously under slight droughtstress condition, and its function in protecting photosynthetic apparatus from photodamagew...