HIGHLIGHTS:
The yellow passion fruit ‘BRS GA1’ is sensitive to salt stress in the successive vegetati-ve/flowering and flowering stages.
In the vegetative/flowering and vegetative/fruiting stages, salt stress reduces leaf water poten-tial drastically.
The current K fertilizer recommendation for ‘BRS GA1’ yellow passion fruit is considered excessi-ve.
ABSTRACT
The objective of this study was to evaluate the effects of saline water irrigation management strategies and potassium doses on the concentration of photosynthetic pigments, gas exchange, and fruit production of ‘BRS GA1’ yellow passion fruit. The experiment was carried out under field conditions using a randomized block design, with treatments based on a 6 × 2 factorial scheme, related to six management strategies for irrigation with saline water (irrigation with low-salinity water throughout the crop cycle-WS; irrigation with high-salinity water in the vegetative stage-VE; flowering stage-FL; fruiting stage-FR; and successively in vegetative/flowering stages-VE/FL and vegetative/fruiting stages-VE/FR) and two doses of potassium (60 and 100% of the recommendation), with four replicates. The dose of 100% recommendation corresponded to 345 g of K2O plant-1 year-1. High electrical conductivity irrigation water (4.0 dS m-1) was used in different phenological stages according to treatment, alternating with water of low electrical conductivity (1.3 dS m-1). The synthesis of chlorophyll a and b, stomatal conductance, instantaneous carboxylation efficiency and water use efficiency of ‘BRS GA1’ yellow passion fruit were reduced under irrigation with water of 4.0 dS m-1 in all strategies adopted. Fertilization with 60% of the K recommendation promoted greater number of fruits and yellow passion fruit yield. Irrigation with 4.0 dS m-1 water in the vegetative/flowering and flowering stages reduced the yield of yellow passion fruit.
Key words:
Passiflora edulis Sims; salt stress; osmoregulation
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In Figure A, means with the same letters indicate no significant differences between saline water irrigation management strategies (Scott-Knott test, p ≤ 0.05). In Figure B, means with the same uppercase letters indicate no significant differences between potassium doses in the same irrigation management strategy by F test at p ≤ 0.05, and same lowercase letter in the same potassium dose indicate no significant difference between saline irrigation management strategies (Scott-Knott test, p ≤ 0.05). Vertical bars represent the standard error (n = 4). WS - irrigation with low-salinity water throughout the cultivation cycle (1-253 days after transplanting - DAT); salt stress in VE = vegetative stage (50-113 DAT); FL = flowering stage (114-198 DAT); FR = fruiting stage (199-253 DAT); VE and FL = vegetative and flowering stages (50-198 DAT); VE/FR = vegetative and fruiting stages (50-113/199-253 DAS).
In Figures A and B, means with the same uppercase letters indicate no significant differences between potassium doses in the same irrigation management strategy by F test at p ≤ 0.05, and same lowercase letter in the same potassium dose indicate no significant difference between saline irrigation management strategies (Scott-Knott test, p ≤ 0.05). In Figure C, means with the same letters indicate no significant differences between saline water irrigation management strategies (Scott-Knott test, p ≤ 0.05). Vertical bars represent the standard error (n = 4). WS - irrigation with low-salinity water throughout the cultivation cycle (1-253 days after transplanting - DAT); salt stress in VE = vegetative stage (50-113 DAT); FL = flowering stage (114-198 DAT); FR = fruiting stage (199-253 DAT); VE and FL = vegetative and flowering stages (50-198 DAT); VE/FR = vegetative and fruiting stages (50-113/199-253 DAS).
Means with the same letters indicate no significant differences between saline water irrigation management strategies (Scott-Knott test, p ≤ 0.05). Vertical bars represent the standard error of the mean (n = 4). WS - irrigation with low-salinity water throughout the cultivation cycle (1-253 days after transplanting - DAT); salt stress in VE = vegetative stage (50-113 DAT); FL = flowering stage (114-198 DAT); FR = fruiting stage (199-253 DAT); VE and FL = vegetative and flowering stages (50-198 DAT); VE/FR = vegetative and fruiting stages (50-113/199-253 DAS).
Means with the same uppercase letters indicate no significant differences between potassium doses in the same irrigation management strategy, by F test at p ≤ 0.05, and same lowercase letter in the same potassium dose indicate no significant difference between saline water irrigation management strategies (Scott-Knott test, p ≤ 0.05). Vertical bars represent the standard error of the mean (n = 4). WS - irrigation with low-salinity water throughout the cultivation cycle (1-253 days after transplanting - DAT); salt stress in VE = vegetative stage (50-113 DAT); FL = flowering stage (114-198 DAT); FR = fruiting stage (199-253 DAT); VE and FL = vegetative and flowering stages (50-198 DAT); VE/FR = vegetative and fruiting stages (50-113/199-253 DAS).
In Figure A, means with the same letters indicate no significant differences between saline water irrigation management strategies (Scott-Knott test, p ≤ 0.05). In Figure B, means with the same uppercase letters indicate no significant differences between potassium doses by F test at p ≤ 0.05. Vertical bars represent the standard error of the mean (n = 4). WS - irrigation with low-salinity water throughout the cultivation cycle (1-253 days after transplanting - DAT); salt stress in VE = vegetative stage (50-113 DAT); FL = flowering stage (114-198 DAT); FR = fruiting stage (199-253 DAT); VE and FL = vegetative and flowering stages (50-198 DAT); VE/FR = vegetative and fruiting stages (50-113/199-253 DAS).