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The synergistic effects of sodium and potassium on the xerophyte Apocynum venetum in response to drought stress
- Cui, Yan-Nong, Xia, Zeng-Run, Ma, Qing, Wang, Wen-Ying, Chai, Wei-Wei, Wang, Suo-Min
- Plant physiology and biochemistry 2019 v.135 pp. 489-498
- Apocynum, drought tolerance, dry environmental conditions, leaves, osmotic pressure, osmotic stress, photosynthesis, plant growth, potassium, seedlings, sodium, sodium chloride, synergism, water content, water stress, xerophytes
- Apocynum venetum is an eco-economic plant species with high adaptability to saline and arid environments. Our previous work has found that A. venetum could absorb large amount of Na+ and maintain high K+ level under saline conditions. To investigate whether K+ and Na+ could simultaneously enhance drought resistance in A. venetum, seedlings were exposed to osmotic stress (−0.2 MPa) in the presence or absence of additional 25 mM NaCl under low (0.01 mM) and normal (2.5 mM) K+ supplying conditions, respectively. The results showed that A. venetum should be considered as a typical K+-efficient species since its growth was unimpaired and possessed a strong K+ uptake and prominent K+ utilization efficiency under K+ deficiency condition. Leaf K+ concentration remained stable or was even significantly increased under osmotic stress in the presence or absence of NaCl, compared with that under control condition, regardless of whether the K+ supply was sufficient or not, and the contribution of K+ to leaf osmotic potential consistently exceeded 37%, indicating K+ is the uppermost contributor to osmotic adjustment of A. venetum. Under osmotic stress, the addition of 25 mM NaCl significantly increase Na+ accumulation in leaves and the contribution of Na+ to osmotic adjustment, thus improving the relative water content, concomitantly, promoting the photosynthetic activity resulting in an enhancement of overall plant growth. These findings suggested that, K+ and Na+ simultaneously play crucial roles in the osmotic adjustment and the maintenance of water status and photosynthetic activity, which is beneficial for A. venetum to cope with drought stress.