2019 ASHS Annual Conference

Waterlogging occurs in many regions of the Southern United States because of poor soil drainage and/or excessive rainfall. Waterlogging is a serious abiotic stress affecting plant growth because it results in the decline in the supplement of oxygen to submerged tissues. Although cucumber (Cucumis sativus L.) is sensitive to waterlogging, its ability to generate adventitious roots facilitates gas diffusion and increase plant survival when the oxygen concentrations are decreased. To gain a better understanding of the physiological responses that enable cucumber plants to survive, in the early season, a 10 d waterlogging experiment was conducted. Thus, the objective of this study was to measure the net photosynthesis and stomatal conductance of cucumber plants under waterlogging conditions and no-waterlogging conditions for 10 days. ‘Straight 8’ cucumber plants were seeded in 4” pots filled with a soilless medium and grown in a plant growth chamber at 23°C/20°C day, night temperature at 16 h photoperiod. They were arranged in a randomized complete block design with four replications. Two weeks after emergence, all cucumber plants were placed in 11 L totes. One-half of the totes were filled with enough water to be 10 cm over the top of the pots to simulate waterlogging conditions for 10 d. The other half of the plants were watered as needed. One day after treatment initiation and over the subsequent 9 d, plants were measured for physiological performance with a Li-6800 (Li-Cor Biosciences) photosynthesis system. Plants were harvested at the end of 10 d and plant height (ht), leaf number and area, fresh mass (FM), and dry mass (DM) were taken for statistical analysis (GLIMMIX; SAS v. 9.4). Results indicated that cucumber plants subjected to the 10 d waterlogging stress conditions were stunted, had fewer leaves, decreased leaf area, FM, and DM. Additionally, those cucumber plants also had a higher DM:FM ratio. Previous research indicated that waterlogging in cucumber plants also had significant differences in shoot dry weight, vine length, and root dry weight. There were also differences in net CO₂ assimilation (A_n) and intercellular CO₂ (C_i) concentrations. Furthermore, there were significant differences in the relationship between stomatal conductance (g_s) and transpiration (T) rate (figure 4) and C_i concentrations. Overall, cucumber plants subjected to a 10 d waterlogging stress period demonstrate decreased growth, A_n and higher C_i concentrations compared to the cucumber plants not subjected to waterlogging stress.