In horticultural practice accelerated plant development and particularly earlier flowering, has been reported with microalgae applications. Therefore, the objective of this work was to study the effects of foliar spraying with Scenedesmus sp. and Arthrospira platensis hydrolysates on Petunia x hybrida plant development and leaf nutrient status. Three treatments were tested: T1 (foliar application with water, the control), T2 (foliar application with Arthrospira), and T3 (foliar application with Scenedesmus). Foliar spraying was applied five times (0, 14, 28, 35, and 42 days after transplanting). The concentration of both microalgae was 10 g L⁻¹. At the end of the trial biometric parameters and nutrient concentration in photosynthetic organs (the leaves) were measured. The results of this assay show that foliar application of Scenedesmus accelerated plant development in terms of higher rates of root growth, leaf and shoot development, and earliness of flowering. Arthrospira enhanced the root dry matter, the number of flowers per plant, and the water content. Nevertheless, a reduction was found in the conductive tissue (stem + petiole) dry weight with Arthrospira compared with Scenedesmus and the control. The results also show that microalgae hydrolysate supply can improve the plant nutrient status. Based on these results, it is advisable to use Scenedesmus hydrolysates in foliar applications to increase the blooming of Petunia x hybrida.

Crop plants are usually nonhalophytes that tolerate only moderate saline concentrations; under salinity, they accumulate salt in their aboveground organs and, to a smaller extent, in roots. Enhanced synthesis of determined secondary metabolites (such as proline, phenolics, or malondyaldehide) under stressful conditions is believed to protect the cellular structures from oxidative damage, in addition to the osmotic advantage for the plants. The aim of this work is to study the influence of the fertigation water salinity on osmoprotectant content in Cordyline fruticosa var. ‘Red Edge.’ Four nutrient solutions with different electrical conductivity levels were applied: EC_1.5 (1.5 dS m⁻¹), EC_2.5 (2.5 dS m⁻¹), EC_3.5 (3.5 dS m⁻¹), and EC_4.5 (4.5 dS m⁻¹), obtained by the addition of different quantities of sodium chloride (NaCl) to a basic nutrient solution (EC 1.5 dS m⁻¹), followed by stirring to dissolve the salt and make the solution homogeneous. The results show that malondialdehyde (MDA) content is not a good indicator of plant stress, as levels in EC_1.5 and EC_4.5 are similar, but flavonoids, phenols and sugars contents are more useful indicators, because the highest values in leaves are found with the more saline treatment. Proline plays an osmoregulatory role, increasing in roots when NaCl concentration in the nutrient solution is too high but also when it is too low.

ISHS International Symposium on Greenhouse Cooling THE RADIATION SPECTRUM THROUGH ORNAMENTAL NET HOUSES AND ITS IMPACT ON THE CLIMATE GENERATED

The Mediterranean area has been experiencing an extensive development of intensive horticulture, with a majority of that located in arid and semi-arid regions with limited water resources and poor water quality. One of the most important greenhouse vegetable crops is melon. This article studies the effects of different nitrogen–potassium (N–K) fertilizers applications and two types of irrigation water on yield and nutritional behavior of melon crop Cucumis melo L. (var. cantalupensis Naud. Alpes). The trial was conducted during two cycles under Mediterranean greenhouse conditions, on sandy mulching soil. The experimental design was bifactorial: NK fertigation and water quality, with three nutrition levels and two water qualities [MS with electrical conductivity (EC) = 0.6 dS m⁻¹ and HS with EC = 2.3 dS m⁻¹]. During the first cycle, the fertigation levels were F₁ (50% NK), F₂ (100% NK), and F₃ (125% NK). In the second cycle, the fertigation levels were F₂, F₄ (125% N and 150% K) and F₅ (180% N and 220% K). Treatment F₂ was the recommended total doses (220 kg N ha⁻¹ and 355 kg K ha⁻¹). The increase in the NK concentration of the nutritive solution produced a rise in commercial production. The salinity of irrigation water did not affect marketable yield but had an effect on the fruit size, which was compensated for by an increase in the amount of fruit produced. Dry-matter production, N, and K uptake by plant (g m⁻²) were evaluated in the first and second trials. Salinity and NK nutrition levels significantly affected (P < 0.05) dry matter and N and K uptake by melon plant. Nitrogen and K uptake present interesting correlations with production and with each other, as established by mean regression analysis.