Abstract Sunlight includes UVA (320–400 nm). Since it is irrelevant for driving photosynthesis, less recognition is given to its usefulness in indoor cultivation. We examined how the cultivation under different UVA levels (0, 10 and 40 μmol m−2 s−1) affects the lettuce postharvest quality by evaluating the temporal dynamics of several underlying aspects, including weight loss, chlorophyll fluorescence, protein content, primary energy reserves (starch, sugars), pigments (chlorophyll, carotenoids), the activity of enzymes related to enzymatic browning [phenylalanine ammonia lyase, polyphenol oxidase (PPO)], the activity of antioxidant machinery enzymes (superoxide dismutase, catalase), the accumulation of non-enzymatic antioxidants (polyphenols, ascorbic acid) and the accumulation of reactive oxygen species (ROS; H2O2, O2−). Evaluations were conducted (5 d intervals) on dark-stored excised leaves for 15 d (16 ℃, 70 % relative air humidity). Control samples gradually underwent a decrease in both primary energy reserves and protein content. They also suffered from color degradation owing to both a decrease in chlorophyll content and an enhanced PPO activity. Increased electrolyte leakage was also observed as a result of enhanced ROS levels. The low UVA level clearly improved all quality parameters, whereas the application of high UVA intensity caused limited effects in comparison to the control. In the former case, ROS accumulation was counteracted by an enhanced stimulation of the non-enzymatic and enzymatic antioxidant machinery. Overall, the results show that the promotive effect of UVA during cultivation on lettuce nutritional quality and shelf-life is strongly intensity-dependent and is mediated by diverse processes.

中文翻译：

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栽培过程中的低 UVA 强度可延长生菜的保质期，这种效果在较高强度下无法持续

摘要 阳光包括 UVA (320–400 nm)。由于它与驱动光合作用无关，因此对其在室内栽培中的有用性的认识较少。我们通过评估体重减轻、叶绿素荧光、蛋白质含量、初级能量等几个基本方面的时间动态，研究了在不同 UVA 水平（0、10 和 40 μmol m−2 s−1）下的栽培如何影响生菜采后质量储备（淀粉、糖类）、色素（叶绿素、类胡萝卜素）、与酶促褐变相关的酶的活性 [苯丙氨酸解氨酶、多酚氧化酶 (PPO)]、抗氧化酶的活性（超氧化物歧化酶、过氧化氢酶）、非酶抗氧化剂（多酚、抗坏血酸）和活性氧（ROS；H2O2、O2−）的积累。在黑暗储存的切下叶子上进行评估（间隔 5 天），持续 15 天（16 ℃，70 % 相对空气湿度）。对照样品的初级能量储备和蛋白质含量逐渐减少。由于叶绿素含量减少和 PPO 活性增强，它们还遭受颜色退化。由于 ROS 水平升高，还观察到电解质泄漏增加。低 UVA 水平明显改善了所有质量参数，而与对照相比，高 UVA 强度的应用造成的影响有限。在前一种情况下，ROS 积累被增强的非酶促和酶促抗氧化机制的刺激所抵消。全面的，