High concentration of salts in the soil impacts the availability of water and nutrients essential for plant growth and physiology. Therefore, management strategies that can mitigate the negative effects of salt stress are necessary, such as the use of plant hormones. Thus, this study aimed to evaluate the effect of salt stress and the application of melatonin on the growth and production aspects of radish plants. The experiment was carried out in a randomized block design, in a 3 × 3 factorial scheme, with four replications, considering one plant per experimental plot. The treatments consisted of three electrical conductivities of irrigation water - ECw (0.5, 2.75, and 5.0 dS m^-1) and three concentrations of melatonin (0, 0.5, and 1.0 mM). Growth variables were evaluated, namely plant height, stem diameter, number of leaves, leaf area, dry mass of leaves, petioles and roots, specific leaf area, leaf area ratio, and leaf weight ratio. In addition, production aspects were analyzed, namely bulb length, bulb diameter, and bulb fresh weight. Exogenous application of melatonin reduces the deleterious effects of salt stress on the growth and production aspects of radish plants. Application of melatonin at a dose of 0.5 mM is the most recommended to mitigate the effects of salt stress up to the level of 2.75 dS m^-1. The use of melatonin opens new perspectives for the development of management strategies aimed at optimizing growth and protecting the radish crop under saline conditions.

Water stress is the main abiotic factor that limits the development and commercial quality of ornamental plants, such as Zinnia elegans. This study aimed to evaluate the ability of exogenous melatonin (MEL) to attenuate the deleterious effects of water deficit by modulating stomatal physiological, biochemical and structural parameters. Z. elegans plants were subjected to four water regimes (80% FC, 20% FC, early stress and late stress) with (1.0 mM) and without MEL application. Severe water stress (20% FC) drastically reduced the rate of CO₂ assimilation (A) by 43.81% and stomatal conductance (gs) by 68.96%. However, the application of MEL significantly mitigated this damage, resulting in an increase in A of 26.99% gs of 43.75%, and relative water content of 28% in plants under severe stress compared with those in untreated stressed plants. The mechanism of action of MEL involves the modulation of stomatal motion and, as suggested, the promotion of osmotic fit and the protection of membrane integrity and photochemical efficiency. Exogenous melatonin acts as an effective bioregulator, improving the tolerance of Z. elegans to water deficit and sustaining its physiological performance and ornamental potential under stress conditions.

Using non-destructive and low-cost methods to determine leaf area has gained important applications. The research objectives were (i) to propose a non-destructive method to estimate the leaf area of castor bean crops and (ii) to build equations that accurately and quickly estimate the leaf area of specie. One thousand healthy and expanded leaves of five castor bean cultivars (New Zealand Purple, Sipeal, Carmencita, Amarelo de Irecê, and IAC-80) were collected, and 200 leaves were collected from each. The maximum length, maximum width, and leaf area were calculated for each leaf. The product between length and width (LW) were calculated. We performed tests with different linear and non-linear regression models between leaf area and linear leaf dimensions of each cultivar. The models used were linear, linear without intercept, and power. The criteria for choosing the best models to estimate the leaf area of castor beans were a higher coefficient of determination, more elevated Pearson’s linear correlation coefficient, lower Akaike information criterion, higher Willmott agreement index, and smallest root mean square error. The equations that presented the best criteria for estimating the leaf area of castor bean cultivars were those that used the product between length and width, compared to equations that used only one leaf dimension. The model ŷ = 0.439 × LW can be used to accurately and quickly estimate the castor bean leaf area through linear measurements of the leaves, using the product between length and width (LW), regardless of the cultivar chosen.

Understanding the leaf area is essential in plant physiology and ecological studies, as it directly influences photosynthesis, transpiration and plant productivity. This study aimed to develop non-destructive allometric models to estimate the leaf area of three species from the Caatinga biome: Cynophalla flexuosa, Libidibia ferrea and Tabebuia aurea. A total of 1293 leaves were collected from these species, scanned, and analysed using ImageJ software to obtain their length, width, and actual leaf area. In addition, the product of length and width was calculated. Linear, power and exponential regression models were used. The best equations were chosen based on the coefficient of determination, Pearson’s linear correlation coefficient, Willmott’s agreement index, mean squared error, root mean squared error, mean absolute error and mean absolute percentage error. The best equations for all species were constructed using linear and power models, which were indicated for accurate prediction of leaf area. These findings confirm the efficiency of allometric equations as a non-destructive method for predicting leaf area, providing an accessible and economical alternative for ecological studies in semi-arid environments.

The use growth regulators from the cytokinins and auxins group has been shown to increase the productivity of certain crops, as they may be involved in the expression of plant sex, although little is known about the action of auxin IBA and cytokinin CPPU on the fruiting of squash, as well as the interaction between both, which makes this field of study promising. Thus, the objective of this study was to induce the fruiting in Atlas squash, by means of different forms of application and proportions of cytokinin and auxin and to evaluate their effects on the physical-chemical characteristics of the fruits. The treatments were composed of six proportions associated with growth regulators and of two forms of application. The experimental design was a randomized block design with four replicates. At 72 days after transplanting, growth and fruit quality analyses were performed. The behavior of the hormones is modulated by their concentration and place of application, and the effect may be beneficial or not. The proportions 50/50% via leaf and 75/25% via ovary were the ones that increased the growth and parameters of fruit quality. The application of CPPU via leaf at higher concentration in proportion decreases quality characteristics such as vitamin C, carotenoids and starch.

Phosphorus (P) is a primordial mineral nutrient for plants, as it is directly linked to physiological and biochemical processes essential for plant maintenance, and can influence the production and final quality of the product. Furthermore, P favors good root development, which can benefit sweet potato crop. Thus, the objective of the work is to assess the influence of increasing doses of P on the production and physical quality of sweet potatoes in two growing seasons in a semi-arid environment. The experiments were carried out from April to August 2021 (season 1) and from December 2021 to April 2022 (season 2) at the Rafael Fernandes Experimental Farm - UFERSA, Mossoró, RN, BR. The design was randomized blocks, with four replications. The treatments consisted of five doses of P (0; 60; 120; 180 and 240 kg ha^-1 of P₂O₅) via fertigation and tested on the sweet potato cultivar Paraná. After harvesting the roots, the number and yield of roots (commercial, non-commercial and total), the average mass and the percentage of commercial roots were evaluated. Commercial roots were evaluated for firmness, elasticity and cooking time. The P doses influenced the production characteristics, mainly at the dose of 60 kg ha^-1 of P₂O₅, which promoted increases in the yield of commercial roots. The doses of P promoted the reduction of firmness for both growing seasons. A dose of 180 kg ha^-1 of P₂O₅ led to the shortest cooking time for the second growing season.