Tomato and cucumber seedlings were grown in a growth chamber to evaluate the effects of different cycles of light–dark exposure conditions (T₀ (control treatment) (1 cycle of 24 h distributed in 18 h of light exposure and six hours of dark), T₁ (two cycles of 12 h distributed in nine hours of light exposure and three hours of dark) and T₂ (three cycles of eight hours distributed in six hours of light exposure and two hours of dark) on growth, nutrient status, pigment concentration and physiological changes. Total dry weight showed different behaviors in both species, since in tomato the total dry weight remained unchanged under varying light–dark cycles, whereas in cucumber seedlings there was a clear decrease compared to the control treatment. In both species, plants grown under T₂ showed the best water content. Nitrogen, P and K content—as well as partitioning in the different organs of the plants—displayed different patterns under varying cycles of light–dark conditions in both species. Chlorophyll (b and a + b) concentration decreased significantly in both species in T₁ and T₂ compared to the control treatment (T₀). At physiological level, the concentration of total soluble sugars and proline in leaf showed the highest value in the control treatment with 18 h of light and six hours of dark.

中文翻译：

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番茄和黄瓜幼苗在不同光暗循环下的生理响应

在生长室中种植番茄和黄瓜幼苗，以评估不同周期的明暗暴露条件（T ₀（对照处理）（1个周期的24小时分布于18小时的光照和6小时的黑暗中）的影响， T ₁（两个周期为12小时，分布在9小时的曝光和3小时的黑暗中）和T ₂（三个小时的八个周期分布在六个小时的光照和两个小时的黑暗中）有关生长，营养状况，色素浓度和生理变化的信息。两种物种的总干重表现出不同的行为，因为在不同的明暗循环下，番茄的总干重保持不变，而与对照相比，黄瓜幼苗的干重明显减少。在两个物种中，在T ₂下生长的植物均显示出最佳的水分含量。氮，磷和钾的含量，以及在植物不同器官中的分配，在两个物种的明暗条件下，在不同的周期下显示出不同的模式。在T ₁和T _2中，两种物种的叶绿素（b和a + b）浓度均显着降低与对照治疗（T ₀）相比。在生理水平上，在光照18 h和黑暗6 h的对照处理中，叶片中总可溶性糖和脯氨酸的浓度显示出最高值。