Effects of exogenous calcium on growth and photosynthetic characteristics of Tagetes erecta under salt-alkali stress
[Objective]This study aims to explore the effects of exogenous CaCl2 on the growth and photo-synthetic characteristics of marigold(Tagetes erecta L.)under saline-alkali stress,and to provide theoret-ical support for the application of CaCl2 to improve the cultivation efficiency and product quality of mari-gold on saline-alkali land.[Methods]Taking marigold seedlings as test materials,pot experiment was car-ried out to observe the growth phenotype,photosynthetic pigment content,photosynthetic gas exchange parameters,and chlorophyll fluorescence parameters of marigold seedlings by watering(CK1),root irriga-tion with 80 mmol/L mixed saline-alkali solution(CK2),and root irrigation with saline-alkali followed by foliar spraying with four concentrations of CaCl2 solution(5,10,15,20 mmol/L].[Results]With the prolongation of saline-alkali stress,the plant height,stem diameter,root configuration,and root-shoot ra-tio of marigold plants showed a gradual upward trend,and the net photosynthetic rate(Pn),transpiration coefficient(Tr),stomatal conductance(Gs),total chlorophyll content(Chl t),and maximum photo-chemical efficiency(Fv/Fm)of leaves showed a downward trend,while intercellular CO2 concentration(Ci)showed an upward trend.After spraying different concentrations of CaCl2 on the leaves,the change of each index was decreased.There was a concentration effect,and the effect of 10 mmol/L CaCl2 treat-ment was the best.On the 20 th day of stress,the Chl t,Pn,Tr,Gs,and Fv/Fm of leaves treated with 10 mmol/L CaCl2 were higher than those of CK2 by 46.78％,45.53％,49.51％,49.57％,and 32.83％,while the root-shoot ratio and Ci were reduced by 22.60％and 30.91％,respectively.[Conclusion]Spra-ying 10 mmol/L CaCl2 on the leaves reduces the decrease of chlorophyll contents in marigold leaves under saline-alkali stress,increases the electron transport rate of PS Ⅱ,enhances the photosynthetic capacity of leaves,and effectively improves the growth of plants.
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