Effect of ethylene pretreatment on tomato plant responses to salt, drought, and waterlogging stress

Abstract

Salinity, drought, and waterlogging are common environmental stresses that negatively impact plant growth, development, and productivity. One of the responses to abiotic stresses is the production of the phytohormone ethylene, which induces different coping mechanisms that help plants resist or tolerate stress. In this study, we investigated if an ethylene pretreatment can aid plants in activating stress-coping responses prior to the onset of salt, drought, and waterlogging stress. Therefore, we measured real-time transpiration and CO₂ assimilation rates and the impact on biomass during and after 3 days of abiotic stress. Our results showed that an ethylene pretreatment of 1 ppm for 4 h did not significantly influence the negative effects of waterlogging stress, while plants were more sensitive to salt stress as reflected by enhanced water losses due to a higher transpiration rate. However, when exposed to drought stress, an ethylene pretreatment resulted in reduced transpiration rates, reducing water loss during drought stress. Overall, our findings indicate that pretreating tomato plants with ethylene can potentially regulate their responses during the forthcoming stress period, but optimization of the ethylene pre-treatment duration, timing, and dose is needed. Furthermore, it remains tested if the effect is related to the stress duration and severity and whether an ethylene pretreatment has a net positive or negative effect on plant vigor during stress recovery. Further investigations are needed to elucidate the mode of action of how ethylene priming impacts subsequent stress responses.

Keywords: abiotic stress; drought; ethylene; hypoxia; priming; salt stress; waterlogging.

FIGURE 1

Effect of salt stress (10 dS/m) in combination with ethylene pretreatment (light blue; 1 ppm for 4 h) or without (green). (a) Average daily CO2 consumption of control (n = 12) and salt‐stressed tomato plants (n = 6) normalized to the CO2 consumption rate of the first day (Day 0). (b) Average daily transpiration of control (n = 12) and salt‐stressed tomato plants (n = 6) normalized to the transpiration of the first day (Day 0). (c) Plant fresh and (d) dry weight, determined at the end of experiment for control (n = 12) and salt‐stressed tomato plants (n = 6). Control is shown in dark blue (n = 12). Error bars represent standard deviation. Significantly different treatments are indicated by different letters, with α = .05 as the threshold for significance.

FIGURE 2

Effect of drought stress in combination with ethylene pretreatment (light blue; 1 ppm for 4 h) or without (green). (a) Average daily CO2 consumption of control (n = 12) and drought‐stressed tomato plants (n = 6) normalized to the CO2 consumption rate of the first day (Day 0). (b) Average daily transpiration of control (n = 12) and drought‐stressed tomato plants (n = 6) normalized to the transpiration of the first day (Day 0). (c) Plant fresh and (d) dry weight, determined at the end of experiment for control (n = 12) and drought‐stressed tomato plants (n = 6). Control is shown in dark blue (n = 12). Error bars represent standard deviation. Significantly different treatments are indicated by different letters, with α = .05 as the threshold for significance.

FIGURE 3

Effect of waterlogging stress in combination with ethylene pretreatment (light blue; 1 ppm for 4 h) or without (green) on the epinastic angles of leaves of different ages for control (n = 12) and waterlogging‐treated tomato plants (n = 6) at three time‐points: (a) prior to the ethylene pretreatment (Day 0); (b) after the ethylene pretreatment (1 ppm for 4 h; day 1); and (c) after 3 days of waterlogging stress. (d) Average daily CO2 consumption of control (n = 12) and waterlogging‐stressed tomato plants (n = 6) normalized to the CO2 consumption rate of the first day (Day 0). (e) Plant fresh and (f) dry weight, determined at the end of experiment for control (n = 12) and waterlogging‐stressed tomato plants (n = 6). Control is shown in dark blue (n = 12). Error bars represent standard deviation. Significantly different treatments are indicated by different letters, with α = .05 as the threshold for significance.

FIGURE 4

Summary of ethylene pretreatment effect on different parameters after 3 days of waterlogging, salt, and drought stress compared to stressed‐only plants. (a) After 3 days of waterlogging stress, plants of both stressed groups showed hypoxia‐induced epinasty, with no difference in epinastic bending in plants subjected to ethylene pretreatment (indicated with gray, horizontal bar). Plants subjected to ethylene pretreatment displayed lower CO₂ assimilation (indicated with red, downward arrow), but no effect on overall fresh and dry weight at the end of the experiment. (b) Ethylene pretreatment did not alleviate the detrimental impact of salt stress on any of the tested parameters. (c) Ethylene pretreatment reduced transpiration rates of drought‐stressed plants and prevented water loss without affecting biomass production.