The University of Adelaide, School of Agriculture, Food and Wine, Private Mail Bag 1, Glen Osmond, SA 5064, Australia.
J Sci Food Agric. 2011 Jul;91(9):1712-21. doi: 10.1002/jsfa.4376. Epub 2011 Mar 29.
The accumulation of L-ascorbate (Asc) in fruits is influenced by environmental factors including light quantity. Fruit exposure to ambient light is often reduced by the surrounding leaf canopy, and can be altered by cultivation practices. The influence of reduced sunlight exposure on the accumulation of Asc and its catabolites was investigated in field-grown berries of the cultivated grapevine Vitis vinifera L. cv. Shiraz.
Growth under sunlight-eliminated conditions resulted in reduced berry fresh weight, chlorosis and a reduced total L-ascorbate pool size. The concentration of the Asc catabolite L-tartaric acid (TA) was reduced in berries grown without light. Conversely, concentrations of oxalic acid (OA), an alternative catabolite of Asc, and malic acid (MA), were unaffected by shading the berries during development. Brief and significant reductions in transcription of the Asc metabolic genes were observed in shade-grown berries after 4 weeks of dark acclimatisation whilst a key TA biosynthetic gene was not regulated by light.
The results demonstrate that light-regulation of Asc and TA occurs only at brief stages of development and that OA and MA accumulation is light independent. Additionally, the comparable ratios of TA product to Asc precursor under both light regimes suggest that the diversion of Asc to TA is driven by factors that are not responsive to light. These findings suggest that an altered light regime is not the key to manipulating TA or MA levels in the harvested berry.
环境因素，包括光照量，会影响水果中 L-抗坏血酸（Asc）的积累。果实暴露在环境光下通常会被周围的树叶树冠遮挡，而种植方式也会改变光照。本研究调查了在田间生长的酿酒葡萄（Vitis vinifera L. cv. Shiraz）浆果中，减少阳光照射对 Asc 和其代谢物积累的影响。
在消除阳光条件下生长导致浆果鲜重降低、黄化和总 L-抗坏血酸池大小减小。在没有光照的情况下，Asc 的代谢物 L-酒石酸（TA）的浓度降低。相反，在发育过程中给浆果遮荫并没有影响 Asc 的替代代谢物草酸（OA）和苹果酸（MA）的浓度。在黑暗适应 4 周后，遮荫浆果中 Asc 代谢基因的转录显著短暂降低，而关键的 TA 生物合成基因不受光照调控。
结果表明，光照仅在发育的短暂阶段调节 Asc 和 TA，而 OA 和 MA 的积累与光照无关。此外，在两种光照条件下，TA 产物与 Asc 前体的可比比例表明，Asc 向 TA 的分流是由对光照不敏感的因素驱动的。这些发现表明，改变光照制度并不是控制收获浆果中 TA 或 MA 水平的关键。
