Effects of Salt Stress on the Growth of Asparagus officinalis L.Seedlings and on Na~+,K~+ and Ca~(2+) Distribution in Them

Asparagus officinalis L.cultivar NJ978 was used to study the growing rate,salt ion content and mineral ion uptake and distribution in the plant under salt stress.The results showed that there was a negative relationship between seedling growth and salt concentration.Seedlings growth was not significantly inhibited under low salt stress(NaCl≤50mmol/L),but high concentrations of NaCl(200-300mmol/L)had a detrimental effect on the growth of A.officinalis.Na+content increased and K+and Ca2+content decreased in A.officinalis roots,stems and leaves with increasing NaCl concentration.Under low salt stress,the seedlings of A.officinalis could inhibit Na+from transporting to the aerial part of the plant by withholding Na+in the root,thus maintaining a relative balance of ions in the aerial part.Under high salt stress(NaCl100mmol/L),the aerial part of seedlings accumulated superabundance of Na+,the uptake of K+and Ca2+was limited,the seedlings were damaged heavily,as was manifested as a rapid decrease in K+/Na+and Ca2+/Na+in the plant.The selective absorption of K+,Ca2+and Na+(ASK,Na and ASCa,Na)was significantly increased with increasing salinity,and the selective transportation of K+and Ca2+(TSK,Na and TSCa,Na)increased at first and then decreased with increasing salinity.The impediment by the root of the upward transport of Na+and the redistribution of ions in the root,the stem and the leaves could be an important mechanism for salt tolerance of A.officinalis.