Effects of alkali stress on the content of mineral elements in different organs of Chloris virgata

Chloris virgata is a naturally occurring alkali-tolerant halophyte. To explore the physiological mechanism underlying the alkali tolerance of C. virgata, we used 150 mmol·L⁻¹ alkaline salt solution ( NaHCO₃ ꞉ Na₂CO₃ = 9 ꞉ 1) to treat C. virgata seedlings for one month. After the alkali stress treatment, we detected different mineral elements (Na, K, Ca, Mg, P, and Fe) and calculated the distribution of each mineral element among different organs (shoots, spikes, and roots). We also observed changes in leaf photosynthesis. The results indicated that long-term alkali stress strongly inhibited leaf photosynthesis and reduced the contents of K, Ca, P, and Mg in different organs. Analysis of the distribution of each element among the three organs showed that the relative contents of Na, K, Ca, Mg, and Fe in shoots were significantly higher than those in spikes and roots under alkali stress (P < 0.05). However, P still largely accumulated in the spike under alkali stress, and the contribution of P to the total element in the spike reached 49.80% under the control condition and 50.02% under the alkali stress condition. Analysis of the contribution percentage of each element to the total showed that K content was much higher than that of other elements in all organs, followed by Ca and P. Under alkali stress conditions, Na was extensively accumulated in all three organs, especially in shoots, where Na accumulation was enhanced from 0.707% to 28.397% by alkali stress. The shoot Na content of the alkali stress treatment was 28.399-fold that of the control treatment. However, under alkaline stress conditions, the spikes of C. virgata maintained a high K content, which supports the normal growth of the spike. In conclusion, C. virgata can complete its life cycle under long-term alkali stress conditions because of its strong ability to regulate Na. C. virgata protects young spikes under long-term alkali stress by enhancing the accumulation of Na in roots and shoots and lowering the accumulation of Na in the spike. C. virgata can also maintain a normal level of P to preserve normal physiological metabolism and relieve the damage caused by alkali stress.