Physiology in Talisia esculenta seedlings under irrigation with saline water on substrate with hydrogel

Salinity interferes in the physiology of seedlings from germination and seedling emergence, so it is necessary to adopt measures to mitigate its effects. The objectives of this research were to evaluate irrigation frequency, saline water, polymer, and container volume in the emergence and physiology of Talisia esculenta (A. St.-Hil.) Radlk. The treatments were obtained from the combination of polymer doses (0.0; 0.2; 0.6; 1.0; and 1.2 g dm-3), electrical conductivities of the irrigation water (0.3; 1, 1; 2.7; 4.3; and 5.0 dS m-1), and irrigation frequencies (daily and alternate), plus two additional treatments to assess the volume of the container. A randomized block design was used. Emergence and leaf indices of chlorophyll, fluorescence, and gas exchange were analyzed 100 days after sowing. The increase in electrical conductivity reduced and delayed seedling emergence. Decreasing irrigation frequency reduced the chlorophyll b index, stomatal conductance, transpiration, net CO2 assimilation, and carboxylation efficiency. The magnitude of the effects of electrical conductivity of water and polymer were associated with the frequency of irrigation. However, both salinity and polymer reduced practically all physiological variables. The reduction in container volume also affected the physiology of the seedlings, with more effects when irrigated on alternate days. The T. esculenta seedlings are considered sensitive to salinity, should be irrigated daily with water with less electrical conductivity than 1.0 dS m-1, as well as higher capacity containers used (0.75 vs 1.30 dm3).

Multivariate classification of cotton cultivars tolerant to salt stress

ABSTRACT Two multivariate methods were adopted to classify salt-tolerant cotton genotypes based on their growth and physiological traits. The genotypes were cultivated in a greenhouse and subjected to 45 days of irrigation with saline water from the V4 phase onwards. Irrigation was performed with saline water with electrical conductivity (ECw) of 6.0 dS m-1. A factorial-randomized block design was adopted with nine cultivars, two treatments of ECw (0.6 as the control, and 6.0 dS m-1), and four replicates. Plants were evaluated for growth, gas exchange, and photosynthesis. The data were statistically analyzed using univariate and multivariate methods. For the latter, non-hierarchical (principal component, PC) and hierarchical (UPGMA) models were used for the classification of cultivars. Significant differences were found between cultivars based on univariate analyses, and the traits that differed statistically were used for multivariate analyses. Four groups were identified with the same composition in both the PC and UPGMA methods. Among them, one contained the cultivars BRS Seridó, BRS 286, FMT 705, and BRS Rubi, which were tolerant to salt stress imposed on the plants. Photosynthesis, transpiration, and stomatal conductance data were the main contributors to the classification of cultivars using the principal component method.

Saline water irrigation strategies and potassium fertilization on physiology and fruit production of yellow passion fruit

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.