Effect of High Greenhouse Irradiance on Growth and Yield Components of Lettuce (Lactuca sativa L.)

In the coming decades, the global average temperature of ۱.۵ ºC is expected, consequently affecting lettuce production and global food security. Thus, the current experiment was carried out to investigate the response of lettuce genotypes grown under varying high daytime temperatures and optimal conditions. Three-week-old seedlings of eight lettuce genotypes were transferred into the two hydroponic systems using a random complete block design. One of the hydroponic systems was retained in the growth chamber (۲۲ ºC) as control while the second system was transferred to the greenhouse, where the heat screening occurred the genotypes placed in the greenhouse were subjected to varying air temperatures (mean ۳۴.۳/۲۹.۲ ºC afternoon/evening) throughout the experiment. Fluctuation in the daytime temperature was determined using the thermo-hygrometer. Growth and yield components were evaluated. Under elevated temperatures, the yield and plant weight of all genotypes screened decreased compared to optimal conditions except SAL۰۹۸, which increased by ۰.۱% and ۴%, respectively. Furthermore, SAL۰۹۸ grown under high temperatures recorded an increase in the number of leaves, root length, biomass, and plant height by ۱۵.۲%, ۰.۹%, ۲۸.۱% and ۲۷%. Under heat stress conditions, all traits were positively correlated with the yield except leaf width, indicating that productive characteristics are essential to enhance productivity at high temperatures. Though a high temperature is a major limiting factor undermining lettuce production in the urban region, SAL۰۹۸ has demonstrated effective adaptive mechanisms and ca n be considered a potential heat-tolerant cultivar for further breeding programs to develop high-yielding heat-tolerant varieties.

کلیدواژه ها:

genotypes ، Lettuce ، High temperature ، yield