Boron and calcium increasePisum sativum seed germination and seedling development under salt stress

A beneficial effect of B and Ca application on symbiotic interaction between legume and rhizobia under saline conditions has recently been shown, suggesting conventional agricultural practices to increase crop salt tolerance. However, nothing is known about application of both nutrients on early events of legume development under salt stress, prior to the establishment of a symbiotic interaction. Therefore, the effects of different levels of B (from 9.3 to 93µM B) and Ca (from 0.68 to 5.44 mM Ca) on seed germination, root elongation, plant development, and mineral composition of pea (Pisum sativum L. cv. Argona) grown under 0 to 150 mM NaCl, were analysed. Development of plants previously germinated in the presence of salt was more impaired than that of plants put under salt stress once seeds were germinated. A NaCl concentration of 75 mM and 150 mM inhibited pea seed germination and seedling growth. The addition of either extra B or extra Ca to the germination solution prevented the reduction caused by 75 mM NaCl but not that of 150 mM NaCl. However, root elongation and plant development under salt stress (75 mM NaCl) was enhanced only by addition of both B and Ca. When plants were cultivated in the absence of external N, N content in roots and shoots originating from seeds was diminished by salt and enhanced by B and Ca, suggesting a role of these nutrients in remobilisation of seed nutrient stores. Salinity also led to an extremely high concentration of Na⁺ ions, and to a decrease of B and Ca concentrations. This can be overcome by addition of both nutrients, increasing salt tolerance of developing pea plants. The necessity of nutritional studies to increase crop production in saline soils is discussed and proposed.