Ion uptake and distribution in Panicum antidotale retz. under salt stress

In the present project, distribution of K +, Na +, Mg 2+ Ca 2+ and inorganic phosphate between the leaves of different age of Panicum antidotale was determined. The plant exposed to high level of salinity experiences a severe reduction in shoot fresh and dry matter yield. Accumulation of Na + in leaves increased with decrease in potassium. However, this antagonistic relationship between Na and K was more in older leaves. Hence lowest K +/Na + ratio in the oldest lamina and highest was observed in youngest. As Na + is translocated mainly through xylem and K + through phloem, the younger leaves close to shoot apex would derive their mineral requirements initially from Phloem. Inflorescence accumulated low Na + and high K + resulting in highest K +/Na + ratio under both non-saline and saline conditions. This could be one of adaptive features for acclimatizing salt stress. Accumulation of Ca 2+ and Mg 2+ also decreased in older leaves particularly under saline conditions. However, accumulation of Ca 2+ and Mg 2+ was higher in older leaves indicating both elements were phloem-immobile. Concentration of phosphate increased with the decreasing age both in the lamina and leaf sheath. Inorganic phosphate was phloem mobile, higher external salinity led to lower phosphate concentration. Overall, the degree of salt-induced inhibition in leaf growth of varying ages, or inflorescence of Panicum antidotale has been correlated with pattern ion distribution, and maintenance of K +/Na + ratio in plant parts. Thus, nutritional distribution in leaves of various ages under salt stress is closely linked with their growth.