Treatment with Calcium Chloride Enhances Water Deficit Stress Tolerance in Viola (Viola cornuta)

Abstract

<jats:p>Water deficit stress can reduce the postproduction shelf life and marketability of floriculture crops. To alleviate the damage by water deficiency, plants need to limit transpirational water loss by inducing stomatal closure. Osmotic stress induces stomatal closure like the response to water deficit stress. It could be used as a convenient tool to enhance water deficit stress tolerance by reducing water loss. The objective of this research was to investigate whether osmotic treatment with a high concentration of chemical solutions could trigger a response to osmotic stress so that stomatal closure can be induced, resulting in enhanced water deficit stress tolerance in viola (<jats:italic>Viola cornuta</jats:italic> ‘Sorbet XP Yellow’). Osmotic treatments with CaCl<jats:sub>2</jats:sub>, Ca(NO<jats:sub>3</jats:sub>)<jats:sub>2</jats:sub>, NaCl, NaNO<jats:sub>3</jats:sub>, BaCl<jats:sub>2</jats:sub>, Ba(NO<jats:sub>3</jats:sub>)<jats:sub>2</jats:sub>, and mannitol were applied at the osmotic potentials (ψ<jats:sub>S</jats:sub>) of −1.3 and −2.0 MPa. Chemical treatments [except Ca(NO<jats:sub>3</jats:sub>)<jats:sub>2</jats:sub>, NaCl, and mannitol] helped to delay wilting and gave a longer shelf life, up to 5.2 days over that of the control, 2.5 days. However, leaf necrosis was observed on the violas treated with NaCl, NaNO<jats:sub>3</jats:sub>, BaCl<jats:sub>2</jats:sub>, Ba(NO<jats:sub>3</jats:sub>)<jats:sub>2</jats:sub>, and mannitol. CaCl<jats:sub>2</jats:sub> was the most effective agent in delaying wilting under water deficit stress in viola without leaf necrosis. Compared with the control, violas treated with CaCl<jats:sub>2</jats:sub> at 200 and 300 m<jats:sc>m</jats:sc> showed an increase in shelf life by 2.6 and 1.2 days, respectively. Stomatal conductance (<jats:italic>g</jats:italic><jats:sub>S</jats:sub>) was reduced within 4 hours after treatment with CaCl<jats:sub>2</jats:sub> compared with that of control violas. Leaf relative water content (RWC) of control violas was dramatically reduced 3 days after treatment and fell below 50% on day 4, while CaCl<jats:sub>2</jats:sub>-treated violas maintained higher leaf RWC (70% to 81%) during the water deficit period. These results indicated that osmotic treatment with the high concentration of CaCl<jats:sub>2</jats:sub> caused stomatal closure, resulting in a reduction of water loss and an extension of shelf life under water deficit stress in viola.</jats:p>

Evaluation of Calcium Application Methods on Delaying Plant Wilting under Water Deficit in Bedding Plants

“…Pre-drench also causes osmotic stress to plants, but the following irrigation might alleviate its impact. Inhibited leaf gas exchange parameters, such as photosynthesis, transpiration, and stomatal conductance, by salt/osmotic stresses, recovered after the normal irrigation in Spinacia oleracea [25], V. cornuta [20], and Abelmoschus esculentus [26]. Especially in CaCl 2treated V. cornuta, the subsequent irrigation increased stomatal conductance gradually and fully restored it within four days after osmotic treatment [20].…”

“…Differences in response to the application methods might be associated with the mode of action of treatment methods. Drench application with a high concentration of chemical solutions reduces the soil water potential and induces osmotic stress to plants [20]. Osmotic stress activates similar mechanisms and physiological changes of water deficit stress [22][23][24].…”

“…Osmotic stress activates similar mechanisms and physiological changes of water deficit stress [22][23][24]. CaCl 2 -induced osmotic stress has been shown to rapidly trigger stomatal closure within 4 hrs after treatment [20]. The early osmotic stress event could help plants reduce transpirational water loss and delay wilting during the subsequent water deficit stress.…”

“…In the aspect of stomatal movements, an increased level of cytosolic calcium induces ion efflux from guard cells and reduces the guard cell volume, closing stomata when plants are exposed to water deficit [19]. Park et al [20] suggested that exogenous treatment of CaCl 2 enhanced water deficit tolerance by promoting stomatal closure and maintaining high relative water content in Viola cornuta without any side effects.…”

Comparative effects of ascobin and glutathione on copper homeostasis and oxidative stress metabolism in mitigation of copper toxicity in rice

“…However, ASC and GSH pretreatments reduced the toxic effect of Cu stress on ASC + Cu and GSH + Cu plants by maintaining appropriate water status (Table 2), which might be related to enhanced Ca 2+ accumulation (Figs. 1D, 3), as Ca 2+ is known to regulate water balance through the stimulation of stomatal closure (Park et al 2020). In addition, a severe accumulation of ROS (O 2 •− and H 2 O 2 ) and MDA in rice plants due to the excess Cu 2+ was observed (Fig.…”