Department of Sustainable Crop Production, Università Cattolica del Sacro Cuore, Via Emilia Parmense 84, 29122 Piacenza, Italy.
Department of Horticulture, Michigan State University, 1066 Bogue Street, East Lansing, MI 48824, USA.
Int J Mol Sci. 2020 Jul 13;21(14):4950. doi: 10.3390/ijms21144950.
In many viticulture regions, multiple summer stresses are occurring with increased frequency and severity because of warming trends. Kaolin-based particle film technology is a technique that can mitigate the negative effects of intense and/or prolonged drought on grapevine physiology. Although a primary mechanism of action of kaolin is the increase of radiation reflection, some indirect effects are the protection of canopy functionality and faster stress recovery by abscisic acid (ABA) regulation. The physiological mechanism underlying the kaolin regulation of canopy functionality under water deficit is still poorly understood. In a dry-down experiment carried out on grapevines, at the peak of stress and when control vines zeroed whole-canopy net CO exchange rates/leaf area (NCER/LA), kaolin-treated vines maintained positive NCER/LA (~2 µmol m s) and canopy transpiration (E) (0.57 µmol m s). Kaolin-coated leaves had a higher violaxanthin (Vx) + antheraxanthin (Ax) + zeaxanthin (Zx) pool and a significantly lower neoxanthin (Nx) content (VAZ) when water deficit became severe. At the peak of water shortage, leaf ABA suddenly increased by 4-fold in control vines, whereas in kaolin-coated leaves the variation of ABA content was limited. Overall, kaolin prevented the biosynthesis of ABA by avoiding the deviation of the VAZ epoxidation/de-epoxidation cycle into the ABA precursor (i.e., Nx) biosynthetic direction. The preservation of the active VAZ cycle and transpiration led to an improved dissipation of exceeding electrons, explaining the higher resilience of canopy functionality expressed by canopies sprayed by kaolin. These results point out the interaction of kaolin with the regulation of the VAZ cycle and the active mechanism of stomatal conductance regulation.
在许多葡萄种植区，由于气候变暖，多次夏季胁迫的发生频率和严重程度都有所增加。基于高岭土的颗粒膜技术是一种可以减轻强烈和/或长时间干旱对葡萄生理负面影响的技术。虽然高岭土的主要作用机制是增加辐射反射，但一些间接作用是通过脱落酸（ABA）调节来保护冠层功能和更快地恢复胁迫。在水分亏缺下，高岭土调节冠层功能的生理机制仍知之甚少。在对葡萄进行的干燥实验中，在胁迫高峰期，当对照葡萄的整树冠净 CO 交换率/叶面积（NCER/LA）为零时，高岭土处理的葡萄仍保持正 NCER/LA（~2 µmol m s）和冠层蒸腾（E）（0.57 µmol m s）。当水分胁迫变得严重时，涂有高岭土的叶片具有更高的叶黄素（Vx）+玉米黄质（Ax）+玉米黄质（Zx）池和明显更低的新黄质（Nx）含量（VAZ）。在水分短缺高峰期，对照葡萄叶片中的 ABA 突然增加了 4 倍，而在涂有高岭土的叶片中，ABA 含量的变化受到限制。总的来说，高岭土通过避免 VAZ 环氧化/去环氧化循环偏离 ABA 前体（即 Nx）生物合成方向，防止了 ABA 的生物合成。VAZ 循环的活性和蒸腾作用的保持导致过剩电子的有效耗散，这解释了高岭土喷雾处理的冠层功能具有更高的恢复能力。这些结果指出了高岭土与 VAZ 循环调节的相互作用以及气孔导度调节的主动机制。
