Photosynthesis and transpiration in relation to ion accumulation inVitex trifoliaunder varied light intensity

Abstract

Land plants are constantly growing in environments not optimal for their growth and development, drought and saline stresses are often encountered by plants. These stresses will significantly affect the transpiration, ion absorption and photosynthesis of the plants. Because the photosynthesis of land plants is always accompanied by transpirational water loss, and because the xylem sap being transported to leaves during the transpiration process is not pure water, this in turn will result in the accumulation of ions in plant leaves. This is because the when the water in the xylem sap is transpired into the air, ions will be left in leaves. For this reason, the ratio between the amount of carbon assimilation and ion accumulation in plants may vary significantly under different environmental conditions even within the same plant. This is an important part of plant metabolism in terms of ionic nutrition and salt resistance. However, the relation between the simultaneous change and accumulation of ions and photosynthetic yield is rarely addressed and little is known about the relationship between the accumulation of ions and photosynthetic assimilatant in Vitex trifolia L, a salt and drought resistant plant, the effect of environmental factors on that relationship is even more scarce. In this paper, the photosynthesis and transpiration in relation to ion accumulation in V. trifolia under varied light intensity (on cloudy / overcast and sunny days, respectively). The diurnal accumulation of photosynthetic assimilatant was calculated through the integration according to the instantaneous photosynthetic rate of leaves against time, and the ion accumulation in leaves was yielded by integrating the instantaneous ion concentration of xylem sap against time. In this way, the ion concentrations, in relation to the transpiration rate and the water potential of V. trifolia, as well as the photosynthetic rate, were analysed on cloudy / overcast and sunny days,

Effects of irrigation methods on transpiration and water use efficiency of tomato

“…When there is a water deficit in plants, leaf stomatal conductance is reduced, thereby reducing transpiration water consumption, and stomatal conductance decreases the number of atmospheric CO2 in plants. Plant photosynthetic assimilation of CO2 is relatively more likely from plant respiration, so the carbon isotope effect will occur and lead to a rise in the δ 13 C value [31] . This study showed that the δ 13 C value and water physiological use efficiency of tomato leaves under high-frequency drip irrigation were significantly higher than those under traditional flood irrigation (Table 3), indicating that during the whole growth period, compared with traditional flood irrigation, tomato plants under highfrequency drip irrigation were in a certain state of water deficit and had higher water use efficiency.…”

“…Plant photosynthetic assimilation of CO2 is relatively more likely from plant respiration, so the carbon isotope effect will occur and lead to a rise in the δ 13 C value [31] . This study showed that the δ 13 C value and water physiological use efficiency of tomato leaves under high-frequency drip irrigation were significantly higher than those under traditional flood irrigation (Table 3), indicating that during the whole growth period, compared with traditional flood irrigation, tomato plants under highfrequency drip irrigation were in a certain state of water deficit and had higher water use efficiency. Osorio et al [32] showed that leaf δ 13 c value was positively correlated with transpiration efficiency, which was consistent with this study.…”

“…Only a small part of the water absorbed by plant roots is used for plant body construction, and the remaining 97%-99.5% is discharged from the body through transpiration [12] . Transpiration not only contributes to the absorption and transport of water and mineral nutrients (such as Ca 2+ and Mg 2+ ) by plants [13][14] , but also contributes to the maintenance of normal body temperature [15] . However, when the water consumption of plant transpiration exceeds the water required for physiological processes such as nutrient transport, photosynthesis, and crop growth, the phenomenon of "luxury transpiration" will occur [16] , resulting in ineffective water loss and reduced water use efficiency.…”