Agricultural and Physiological Responses of Tomato Plants Grown in Different Soilless Culture Systems with Saline Water under Greenhouse Conditions.

Tomato is the most important horticultural crop in the world. The yields for this crop are highest in Southeastern Spain. In this work we studied a commercial variety of tomato, with different soilless culture systems (deep flow technique, nutrient film technique, and the perlite substrate) and three levels of salinity (2.2, 6.3, and 10.2 dS·m-1) typical of Southeastern Spain. The irrigation management was carried out for optimizing the water use efficiency. Alterations in the water status of the plants, Cl- and Na+ toxicity, and nutritional imbalances altered the vegetative growth and physiology of the plants. The marketable yield was affected by both soilless culture system and salinity. Regarding the soilles culture system, yield decreased in the order: deep flow technique > perlite > nutrient film technique. The salinity treatments improved the fruits quality by increasing the total soluble solids and titratable acidity. Plants cultivated with the nutrient film technique had the highest concentrations of Cl- and Na+ and the highest Na+/K+ ratio. The concentrations of Cl- and Na+ in the plants were not related directly to the yield loss. Therefore, the influence of the toxicity, osmotic effect, and nutritional imbalance seems to have been responsible for the yield loss.

Foliar potassium nitrate application improves the tolerance of Citrus macrophylla L. seedlings to drought conditions.

Scarcity of water is a severe limitation in citrus tree productivity. There are few studies that consider how to manage nitrogen (N) nutrition in crops suffering water deficit. A pot experiment under controlled-environment chambers was conducted to explore if additional N supply via foliar application could improve the drought tolerance of Citrus macrophylla L. seedlings under dry conditions. Two-month-old seedlings were subjected to a completely random design with two water treatments (drought stress and 100% water/field capacity). Plants under drought stress (DS) received three different N supplies via foliar application (DS: 0, DS + NH4NO3: 2% NH4NO3, DS + KNO3: 2% KNO3). KNO3-spraying increased leaf and stem DW as compared with DS + NH4NO3 and DS treatments. Leaf water potential (Ψw) was decreased by drought stress in all the treatments. However, in plants from DS + NH4NO and DS + KNO3, this was due to a decrease in the leaf osmotic potential, whereas the decrease in those from the DS treatment was due to a decrease in the leaf turgor potential. These responses were correlated with the leaf proline and K concentrations. DS + KNO3-treated plants had a higher leaf proline and K concentration than DS-treated plants. In terms of leaf gas exchange parameters, it was observed that net assimilation of CO2 [Formula: see text] was decreased by drought stress, but this reduction was much lower in DS + KNO3-treated plants. Thus, when all results are taken into account, it can be concluded that a 2% foliar-KNO3 application can enhance the tolerance of citrus plants to water stress by increasing the osmotic adjustment process.