Effects of Drought Stress on Shaded and Non-Shaded Bermudagrass.

Shade and drought are abiotic stresses that commonly occur simultaneously in managed turfgrass systems. How these two stresses interact to affect turfgrass physiology has not been directly investigated. A greenhouse study was conducted to test the hypothesis that shade would decrease the effects of drought stress on two warm-season turfgrasses: common bermudagrass [Cynodon dactylon (L.) Pers ‘Celebration’] and hybrid bermudagrass (C. dactylon x C. transvaalensis ‘Latitude 36’). Grasses were established from washed sod in 45cm deep by 10cm diameter pots filled with a 1:1 top soil: sand rootzone and clipped weekly to a height of 5 cm. The experiment was arranged as a randomized complete block modified split plot design where light quantity was the whole main plot, while genotype and irrigation factors were randomized within light treatments. Low light and high light treatments were applied using a black shade fabric (nominal 40% shade) or supplemental lighting (high pressure sodium), respectively. Irrigation was applied twice per week by hand with treatments being well-watered (100% ET) or drought-stressed (50% ET). After 9 months under ambient conditions, light treatments were implemented for a 9-week period with irrigation treatments initiated 2 weeks after shade treatment. Normalized difference vegetation index (NDVI) and gross photosynthesis rate were measured weekly while leaf relative water content was measured bi-weekly. Also, electrolyte leakage was measured four times at 0, 4, 6 and 8 weeks. Results from two repeated experiments will be discussed.

Keyword: Gross photosynthesis rate, relative water content, electrolyte leakage, NDVI, shade, Celebration, Latitude 36.