University of Bonn, Institute of Crop Science and Resource Conservation, Horticultural Science Department, Auf dem Huegel 6, D-53121, Bonn, Germany.
University of Bonn, Institute of Crop Science and Resource Conservation, Plant Nutrition Department, Karlrobert-Kreiten-Strasse 13, D-53115, Bonn, Germany.
Plant Physiol Biochem. 2018 Nov;132:229-237. doi: 10.1016/j.plaphy.2018.08.042. Epub 2018 Sep 3.
Adjuvants such as surfactants are commonly incorporated into agrochemical formulations to enhance the biological efficiency of foliar sprays by improving the wetting behavior of the spray and/or the penetration of the active ingredients into the leaf tissues. Penetration accelerating adjuvants are known to increase the cuticular permeability and may alter the cuticular barrier to water loss. However, none or very little emphasis has been given to the impacts of adjuvants on crop water balance or drought tolerance, a very important factor affecting crop performance under water scarcity. Two model crops with strongly varying leaf traits, kohlrabi (Brassica oleracea) and apple (Malus domestica) seedlings were grown in controlled environments. Three adjuvants with varying solubility in the cuticle, i.e. octanol-water partition coefficients (logKow) were selected: rapeseed methyl ester (RME) and the surfactants alkyl polyglycoside (APG) and polyoxyethylated tallow amine (POEA). The higher the logKow of the adjuvant, the stronger was the increase of minimum epidermal conductance (g, an essential parameter describing plant drought tolerance). However, such effects depended on the physio-chemical properties of the leaf surface. In comparison to kohlrabi, the adjuvant effects on g of apple leaves were relatively weak. The increase of g was associated with a decrease in contact angle and with an alteration of the wax microstructure. Furthermore, POEA affected photochemical efficiency of kohlrabi leaves. Some adjuvants could have a temporal influence on transpirational water loss and g At repeated applications, they might alter the effective water use and possibly reduce drought tolerance of some horticultural crops.
增效剂（如表面活性剂）通常被加入到农用化学品制剂中，以通过改善喷雾的润湿性能和/或活性成分向叶片组织中的渗透来提高叶面喷雾的生物效率。众所周知，渗透促进增效剂可以增加角质层的通透性，并可能改变角质层对水分流失的屏障。然而，增效剂对作物水分平衡或耐旱性的影响却很少或根本没有得到重视，而水分亏缺条件下影响作物性能的一个非常重要的因素。选用了两种具有不同叶片特性的模式作物，即球茎甘蓝（Brassica oleracea）和苹果（Malus domestica）幼苗，在受控环境中进行种植。选择了三种在角质层中溶解度不同的增效剂，即菜籽油甲酯（RME）、烷基糖苷（APG）和聚氧乙基化牛油胺（POEA），它们的辛醇-水分配系数（logKow）不同。增效剂的 logKow 值越高，最小表皮电导率（g，描述植物耐旱性的一个重要参数）的增加就越强烈。然而，这些影响取决于叶片表面的物理化学性质。与球茎甘蓝相比，苹果叶片的增效剂对 g 的影响相对较弱。g 的增加与接触角的降低和蜡质微观结构的改变有关。此外，POEA 还影响了球茎甘蓝叶片的光化学效率。一些增效剂可能会对蒸腾失水和 g 产生暂时的影响。在重复使用时，它们可能会改变某些园艺作物的有效用水，并可能降低其耐旱性。
