Agronomical, physiological and biochemical effects of zinc applications on cucumber plant growed under high temperature stress

Cucumber (Cucumis sativus L.) is one of the most widely cultivated and consumed vegetables worldwide, characterized by its high water content and rich nutritional value, making it an important food source for human health. This study investigated the effects of different doses of zinc (Zn) and salicylic acid (SA) on the agronomic, physiological, and biochemical characteristics of cucumber plants. The experiment was conducted in a producer-owned greenhouse located in Gürbaraz Hamlet, Özbek Village, İdil District, Şırnak Province, using the Champion F1 cucumber variety. The study was designed with two main treatments: control conditions and drought stress conditions, the latter imposed by reducing irrigation levels to 50% and 75%. A total of 21 treatment combinations were evaluated: Control, Stress (75%), Control+Zn1, Control+Zn2, Control+Zn3, Control+SA1, Control+SA2, Control+SA3, Stress75+Zn1, Stress75+Zn2, Stress75+Zn3, Stress50+Zn1, Stress50+Zn2, Stress50+Zn3, Stress75+SA1, Stress75+SA2, Stress75+SA3, Stress50+SA1, Stress50+SA2, and Stress50+SA3. Zn and SA were applied foliarly four times at 15-day intervals. The experiment was arranged in a randomized complete block design with two replications. Following the treatments, plant vegetative parameters, including leaf fresh and dry weight, chlorophyll content (SPAD), leaf temperature, and relative leaf water content, were measured. Fruit samples were analyzed for fruit length, diameter, firmness, weight, electrical conductivity (EC), color, fresh and dry weight, pH, soluble solids content (SSC), and total yield. Additionally, macro- and microelement contents in fruits, enzyme activities in leaves, and phenolic compounds in fruits were determined. The results indicated that drought stress treatments negatively affected overall yield compared to normal conditions. However, under drought stress, some fruit quality traits and mineral contents were enhanced by salicylic acid applications.