SALINITY- INDUCED STRESS IN GREENHOUSE CROPS IN ALLEVIATED BY POTASSIUM NITRATE -ENHANCED NUTRITION

     The use of enhanced potassic plant nutrition is an efficient method of preventing sodium-induced stress in many crops. In addition, the use of enhanced nitrate fertilization is a potent tool in precluding chloride-induced stress in many crops. The application of Multi-K (potassium nitrate) is shown here as a very efficient method of combating the aforementioned stresses and enhancing crop performances under saline conditions. This concept is validated here for three salinity-sensitive vegetables: tomato, lettuce and Chinese cabbage. By integrating Multi-K in their nutrition programs, these crops were better able to cope with salinity conditions despite higher EC levels. Salination (50 mM NaCl) of the nutrient solution of greenhouse tomatoes markedly decreased K content of the leaves, fruit-set rate, number of flowers, dry weights of the plants, fruit sizes and stem heights. Adding Multi-K at 2, 4 or 8 mM to the salinized nutrient solution reversed these effects, despite a marked increase in EC. Moreover, several vegetative and yield parameters were improved over the non-salinized controls. Three levels of Multi-K (1, 5 and 10 mM) were tested on salinized (52 mM of Cl^-) hydroponically grown lettuce and Chinese cabbage. The highest yields of fresh weight of both crops were obtained from the 5 mM Multi-K treatment. Salination increased the concentration of Na and Cl in plant tissue and reduced the levels of N and K; the opposite occurred in plants fed by the medium and high levels of Multi-K. All the aforementioned results clearly demonstrate that plants can successfully cope with stresses imposed by 30-50 mM Na and Cl, providing that they are continuously supplied with Multi-K at 2–8 mM. A generalized model explains all phenomena involved.

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