Leaf wetting mitigates midday depression of photosynthesis in tomato plants

Abstract

We studied the effects of leaf wetting on midday depression of photosynthesis regarding plant water balance and leaf morphological traits. The plants without leaf wetting showed a significant reduction in midday photosynthesis with a concomitant decrease with leaf conductance, because of lower leaf water potential (-1.3 MPa) due to excessive transpiration water loss. However, midday depression was not observed in the plants with leaf wetting. Lower contact angle between leaf surface and water droplet showed that tomato leaves have lower water repellency. However, water on the leaf surface completely dried within 20 min indicating that effect of water coverage on stomata for CO2 uptake was small. In addition, leaf wetting significantly decreased evaporative demands, which contributed to maintaining appropriate water balance and avoided midday stomatal closure, and it contributed to mitigation of midday depression of photosynthesis.Additional key words: plant water relations; photosynthetic rate; stomatal conductance; transpiration rate; whole-plant chamber. temperature; VPD -vapor pressure deficit; VPDair-to-leaf -vapor pressure deficit between air and leaf; Ψw -leaf water potential.

Foliar water and solute absorption: an update

“…The importance of leaf wetting has also been considered in few ecophysiological studies that assessed how foliar deposition of fog (Hanba et al, 2004;Yokoyama et al, 2019) or sprinkler irrigation (Urrego-Pereira et al, 2013) affected the rate of photosynthesis and transpiration, as recently discussed by Binks et al (2020). The process of stomatal uptake is, however, complex and heterogeneous , as described below.…”

Jasmonic acid and salicylic acid play minor roles in stomatal regulation by CO2, abscisic acid, darkness, vapor pressure deficit and ozone

“…At the same time, MeJA and SA in concentrations up to 200 and 1000 µM, respectively, did not induce a prominent reduction of stomatal conductance, which would be comparable with that in plants treated with 5 µM ABA (Figures 6b,c and Figure S9). However, MeJA suppressed the stomatal opening induced by brief leaf wetting/high humidity in the chambers (Panchal et al., 2016; Yokoyama et al., 2019), and further induced detectable slight stomatal closure. In 80 min after spraying, stomatal conductance in MeJA‐treated plants was significantly reduced by 5–10% of the initial values (Figure S9).…”

Diurnal kinetics related to physiological parameters in Pistacia vera L. versus Pistacia atlantica Desf. under water stress conditions

“…photosynthesis (Hirasawa and Hsiao 1999;Maai et al 2020). The depression of photosynthesis at midday has been recorded in many C 3 species (Pettigrew et al 1990;Quick et al 1992;Yokoyama et al 2019).…”

“…According to Xu and Shen (2005) report, environmental condition (temperature, light and water stress) is the major determinant factor of midday depression. The increase of leaf temperature induces a reduction of stomatal conductance (gs) in most plant species (Dai et al 1992;Franks and Farquhar 1999;Yokoyama et al 2019). Stomatal closure decreases net photosynthesis through a decrease of CO 2 availability, limiting the activity of ribulose 1.5-bisphosphate carboxylase/oxygenase (Rubisco) and intensifying photoinhibition (Crafts-Brandner and Salvucci 2000;Salvucci and Crafts-Brandner 2004a;Yokoyama et al 2019).…”

“…The increase of leaf temperature induces a reduction of stomatal conductance (gs) in most plant species (Dai et al 1992;Franks and Farquhar 1999;Yokoyama et al 2019). Stomatal closure decreases net photosynthesis through a decrease of CO 2 availability, limiting the activity of ribulose 1.5-bisphosphate carboxylase/oxygenase (Rubisco) and intensifying photoinhibition (Crafts-Brandner and Salvucci 2000;Salvucci and Crafts-Brandner 2004a;Yokoyama et al 2019). High leaf temperature induces oxidative stress, leading to the inactivation of many chloroplast enzymes and thus photosynthesis reduction (Dekov and Tsonev 2000;Hu et al 2020).…”