NaCl affects photosynthetic and stomatal dynamics by osmotic effects and reduces photosynthetic capacity by ionic effects in tomato

Abstract

NaCl stress affects stomatal behavior and photosynthesis, by a combination of osmotic and ionic components, but it is unknown how these components affect stomatal and photosynthetic dynamics. Tomato (Solanum lycopersicum) plants were grown using a reference nutrient solution (Control, EC: 2.3 dS m -1), a solution containing additional macronutrients (osmotic effect; EC: 12.6 dS m -1), or a solution with additional 100 mM NaCl (osmotic and ionic effects; EC: 12.8 dS m -1). Steady-state and dynamic photosynthesis along with leaf biochemistry were characterized throughout leaf development. The osmotic effect decreased steady-state stomatal conductance, while speeding up stomatal responses to light intensity shifts. After 19 days of treatment, photosynthetic induction was reduced by the osmotic effect, which was attributable to lower initial stomatal conductance due to faster stomatal closing rate under low light. Ionic effects of NaCl were barely observed in dynamic stomatal and photosynthetic behavior, but led to a reduction in leaf photosynthetic capacity, CO2 carboxylation rate and stomatal conductance in old leaves after 26 days of treatment. With increasing leaf age, rates of light-triggered stomatal movement and photosynthetic induction decreased across treatments. We conclude that NaCl impacts dynamic stomatal and photosynthetic kinetics by osmotic effects and reduces photosynthetic capacity by ionic effects.

Salt-Induced Early Changes in Photosynthesis Activity Caused by Root-to-Shoot Signaling in Potato

“…The results of this work demonstrate the suppressive effect of salinity on the activity of photosynthesis and transpiration in the leaves of potato plants. This fact is consistent with the previously described negative effects of salt of a similar concentration range on other plants [20,42,45,46]. Both salt concentrations (100 and 200 mM) used in the experiments caused unidirectional changes, but the amplitude of the changes was greater when the higher concentration was used.…”

“…Secondly, salinity leads to a change in the ratio of potassium/sodium ions, which affects the course of many metabolic potassium-dependent processes in the cell: the Calvin-Benson cycle, the phenylpropanoid pathway, glycolysis, and the synthesis of starch [9,[16][17][18][19]. In studies on the effect of salinity on photosynthesis, a wide range of concentrations are used-from 20 mM to 400 mM NaCl-and all of them negatively affect photosynthesis [20][21][22][23][24][25][26][27][28][29].…”

Vermicompost Improves Tomato Yield and Quality by Promoting Carbohydrate Transport to Fruit under Salt Stress

“…In general, sodium chloride (NaCl) is the primary salt in salinized soils that is most detrimental to plants. By causing osmotic stress and ion toxicity in tissues, salt stress inhibits plant growth and development [22]. Osmotic stress causes water shortage in plant tissues and induces stomatal closure in leaves, thereby reducing photosynthetic efficiency [23,24].…”

Plants’ Response to Abiotic Stress: Mechanisms and Strategies

“…The osmotic stress signal generated early in salt stress causes plants to be more tolerant of high salt and drought through reducing stomatal opening to reduce water loss [ 25 ]. Moreover, this signal accelerates the rate of stomatal movement under dynamic light, and osmotic stress accelerates stomatal closure when switching between strong and weak light intensities [ 26 ]. Plants are able to efficiently use Na + and Cl − in vesicles and organic solutes in vivo for osmoregulation to avoid ion toxicity.…”