Abstract
Reactive oxygen species (ROS) have been established to participate in stomatal closure induced by live microbes and microbe-associated molecular patterns (MAMPs). Chlorella as a beneficial microorganism can be expected to trigger stomatal closure via ROS production. Here, we reported that Chlorella induced stomatal closure in a dose-and time-dependent manner in epidermal peels of Vicia faba. Using pharmacological methods in this work, we found that the Chlorella-induced stomatal closure was almost completely abolished by a hydrogen peroxide (H2O2) scavenger, catalase (CAT), significantly suppressed by an NADPH oxidase inhibitor, diphenylene iodonium chloride (DPI), and slightly affected by a peroxidase inhibitor, salicylhydroxamic acid (SHAM), suggesting that ROS production involved in Chlorella-induced stomatal closure is mainly mediated by DPI-sensitive NADPH oxidase. Additionally, Exogenous application of optimal concentrations of Chlorella suspension improved instantaneous water use efficiency (WUEi) in Vicia faba via a reduction in leaf transpiration rate (E) without a parallel reduction in net photosynthetic rate (Pn) assessed by gas-exchange measurements. The chlorophyll fluorescence and content analysis further demonstrated that short-term use of Chlorella did not influence plant photosynthetic reactions center. These results preliminarily reveal that Chlorella can trigger stomatal closure via NADPH oxidase-dependent ROS production in epidermal strips and improve WUEi in leave levels.
Highlights
Stomata are natural microscopic pores located in the epidermis of the aerial parts of plants that play a pivotal role in regulating influx of CO2 for photosynthesis and water loss through transpiration [1]
Chlorella-induced stomatal closure in broad bean To determine whether Chlorella has any effect on stomatal movement, the abaxial epidermal peels of broad bean were separately treated with 1.06106, 1.06107, 1.06108, 1.06109 and 1.061010 ind mL21 of Chlorella suspension
We found that Chlorella as an available autotrophic microorganism induced stomatal closure in epidermal strips of broad beans in a dose-and time-dependent manner, arriving at the maximum effect at 1.06109 ind mL21 of Chlorella suspension and 2 h after treatment (Figure 1)
Summary
Stomata are natural microscopic pores located in the epidermis of the aerial parts of plants that play a pivotal role in regulating influx of CO2 for photosynthesis and water loss through transpiration [1]. As the stomatal aperture decreases above the threshold, leaf transpiration rates always diminish prior to the CO2 assimilation rates, favoring a higher instantaneous water use efficiency (WUEi) [3,4,5]. It provides a basis for the suggestions that partial closure of the stomata might conduce to the improvement of WUEi in plants [4,6]. We explore whether Chlorella can be sensed by guard cells to induce partial stomatal closure and improve WUEi of plants when applied as foliar spray
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