HIGHLIGHTS:
Potassium with 98% of the recommendation increased the chlorophyll b in plants under water salinity of 1.3 dS m-1.
The reduction in Fv/Fm indicates that photosynthetic performance was compromised by photoinhibitory damage.
The absolute and relative growth rates in stem diameter of the custard-apple decreased regardless of the potassium dose.
ABSTRACT
The salt stress caused by irrigation water with high concentration of salts stands out as one of the main limiting factors in agricultural production in the semiarid region of Northeastern Brazil. In this context, the objective of this study was to evaluate the photosynthetic pigments, the photochemical efficiency, and the growth of custard-apple irrigated with saline water and potassium doses. The research was carried out under field conditions in a randomized block design in a 2 × 5 factorial scheme, corresponding to two values of electrical conductivity of irrigation water - ECw (1.3 and 4.0 dS m-1) and five potassium doses (50, 75, 100, 125 and 150% of the recommendation). The dose referring to 100% corresponded to the application of 20 g of K2O per plant per year. ECw of 4.0 dS m-1 reduced the synthesis of chlorophyll a, total chlorophyll, and carotenoids in custard-apple, at 245 days after transplanting. Fertilization doses of 50 to 150% of the recommendation inhibited the synthesis of chlorophyll b and the absolute and relative growth rates in stem diameter of custard-apple plants irrigated with water of highest electrical conductivity. Reduction in the quantum efficiency of photosystem II in custard-apple cultivated under ECw of 4.0 dS m-1 is related to photoinhibitory damage to photosystem II. Potassium fertilization did not alleviate the stress caused by water salinity on the growth of custard-apple, during 151-245 days after transplantation.
Key words:
Annona squamosa L.; salinity; mitigation
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EFP - End of formative pruning; DV- Determination of photosynthetic pigment variables, photochemical efficiency and growth
Means followed by different letters indicate a significant difference between treatments by F test (p ≥0.05); Vertical bars represent the standard error of the mean (n = 4)
Means followed by different letters indicate a significant difference between treatments by F test (p ≥ 0.05); Vertical bars represent the standard error of the mean (n = 4)
Means followed by different letters indicate significant difference between water electrical conductivities by F test (p ≥ 0.05); Vertical bars represent the standard error of the mean (n = 4)