Effect of water deficit on survival, growth, gas exchange and water relations of Cupressus arizonica and C. sempervirens var. fastigiata seedlings

Nowadays, the development of green space with ornamental species of cypress is a common in different dry areas of Iran. Regarding the limitation of water resources in dry areas, study on the response of cypresses to drought is essential. This study was carried out to recognize the responses of survival, growth, gas exchange and water relations in seedlings of two cypress species (Cupressus arizonica and C. sempervirens var. fastigiata) under water deficit condition in greenhouse. The experiment was conducted as complete randomized block design with different watering levels (3, 6 and 9 days) in three replicates. Results showed that water deficit had a significant effect on most of the traits measured in seedlings. Survival of C. sempervirens at 9-day irrigation was decreased about 50.2% but in C. arizonica seedling no mortality was detected in each watering level. During drought application, shoot growth and diameter growth in both species prominently decreased, while at 6- and 9-day irrigation, shoot growth in C. arizonica was 43-47% greater than that in C. sempervirens. With increasing drought, photosynthesis activity, stomotal conductance and water potential decreased but intracellular CO2 concentration (Ci) and leaf temperature did not change. Transpiration rate and relative water content (RWC) of leaf were significantly decreased in both species, but in C. arizonica the decrease of transpiration rate at 6- and 9-day irrigation was 12-32/3% less than that in C. sempervirens. Generally, it can be stated that C. arizonica seedling is more tolerant than C. sempervirens seedling under drought stress.