National Wine and Grape Industry Centre, School of Agricultural and Wine Sciences , Charles Sturt University , Locked Bag 588, Wagga Wagga, NSW 2678 , Australia.
AoB Plants. 2011;2011:plr023. doi: 10.1093/aobpla/plr023. Epub 2011 Aug 12.
Covering whole vines with shade cloth is used to protect the vines from heat stress, but may have costs on vine productivity through reduced light availability. Our aim was to assess the carbon balance of vines growing with and without shade to quantify the impact of the covering.
Whole vines were covered with 70 % shade cloth, and shoot leaf area and leaf, stem and bunch growth were followed over two growing seasons. Photosynthesis was measured in situ in all leaves along selected shoots over the growing season. A carbon balance was constructed from the difference in acquisition of carbon and the sequestration of carbon as biomass across the growing seasons.
Shade covering had no initial impact on shoot growth but later reduced leaf growth and later still bunch growth. Stem growth was unaffected. Photosynthetic properties were characteristic of shade leaves, with lower rates and lower light saturation compared with well-exposed leaves. Overall, net photosynthesis was reduced by 40 % by the shade covering and was attributed to the reduced photon flux densities. From the carbon balance, vines were reliant on carbon reserves over 6 weeks after budbreak until current photosynthate increased sufficiently to supply the growth. Shade covering impacted most on biomass accumulation to leaves and bunches at the stage when the vines became autotrophic, consistent with the reduction in carbon acquisition. The markedly high carbon demand by bunches caused a mid-season negative carbon balance, implying that shoots had to draw further on reserves to supply the carbon.
Shade covering over whole grapevines exacerbated the imbalance between the supply of and demand for carbon and greatly reduced vine biomass, especially reproductive allocation. Covering vines with shade cloth to protect the vines from heat events, therefore, had major costs in the carbon economy.
用遮阳网覆盖整个藤蔓，以保护藤蔓免受热应激，但可能会通过减少光照而降低藤蔓的生产力。我们的目的是评估有和没有遮阳网的藤蔓的碳平衡，以量化覆盖的影响。
整株藤蔓都用 70%的遮阳网覆盖，并在两个生长季节中跟踪新梢叶片面积和叶片、茎和果穗的生长情况。在整个生长季节中，在选定的新梢上的所有叶片上进行了原位光合作用测量。通过在生长季节中获取的碳与作为生物量的碳的封存之间的差异来构建碳平衡。
遮阳网覆盖物最初对新梢生长没有影响，但后来减少了叶片生长，再后来则减少了果穗生长。茎的生长不受影响。光合特性是遮荫叶的特征，与充分暴露的叶片相比，其速率和光饱和更低。总的来说，遮阳网覆盖物减少了 40%的净光合作用，这归因于光量子通量密度的降低。从碳平衡来看，在萌芽后 6 周内，葡萄藤依赖于碳储备，直到当前的光合作用产物增加到足以供应生长为止。遮阳网覆盖物对叶片和果穗的生物量积累影响最大，因为葡萄藤在成为自养生物的阶段，对碳的获取减少。果穗对碳的高需求导致了中期的负碳平衡，这意味着新梢必须进一步消耗储备来供应碳。
用遮阳网覆盖整个葡萄藤加剧了碳的供应和需求之间的不平衡，并大大减少了葡萄藤的生物量，特别是生殖分配。因此，用遮阳网保护葡萄藤免受热应激的影响，在碳经济方面代价高昂。
