ABSTRACT
Seed heteromorphism provides plants with alternative strategies for survival in unfavourable environments. However, the response of descendants from heteromorphic seeds to stress has not been well documented. Suaeda aralocaspica is a typical annual halophyte, which produces heteromorphic seeds with disparate forms and different germination characteristics. To gain an understanding of the salt tolerance of descendants and the impact of seed heteromorphism on progeny of this species, we performed a series of experiments to investigate the plant growth and physiological parameters (e.g. osmolytes, oxidative/antioxidative agents and enzymes), as well as expression patterns of corresponding genes. Results showed that osmolytes (proline and glycinebetaine) were significantly increased and that excess reactive oxygen species ([Formula: see text] H2O2) produced under high salinity were scavenged by increased levels of antioxidant enzymes (superoxide dismutase, ascorbate peroxidase and glutathione reductase) and corresponding antioxidants (ascorbic acid and glutathione). Moreover, enhancement of phosphoenolpyruvate carboxylase activity at high salt intensity had a positive effect on photosynthesis. The descendants from heteromorphic seeds presented no significant difference in performance with or without salinity. In conclusion, we found that high salinity induced the same active physiological responses in plants from heteromorphic seeds of S. aralocaspica, there was no carry-over of seed heteromorphism to plants: all the descendants required salinity for optimal growth and adaptation to their natural habitat.
ABSTRACT
As soil salinity constitutes a major threat to agriculture in the world, to cope with this problem, much emphasis has been focused on the response mechanism of halophytes or salt-tolerant species to salinity stress. In the present study, C. album was treated with long-term NaCl and KCl stress, then several parameters were assayed in leaves as follows: inductively coupled plasma atomic emission spectrometry (ICP-AES) was employed to measure the K, Na content; semi-quantitative RT-PCR was used to investigate the expression level of three genes which were related to ion transport on the vacuolar membrane-NHX, VP1 and VAP-C. In addition, the mechanism for the effect of different salinity on K, Na content was preliminarily discussed. The results were as follows: (1) Under lower concentration of NaCl stress, C. album had a preferential uptake of potassium and exclusion of sodium, and thus maintained a low concentration of sodium in cells of the leaf; (2) Under higher concentration of NaCl (300 mmolx L(-1)), C. album was able to tolerate excessive amounts of sodium in cells and kept the higher K/Na ratio in cytoplasm by compartmentalizing Na ions into the vacuole via ion transporter system located on vacuole membrane, (3) Much K ions and total ions (including sodium and potassium) may be responsible for, at least partial, the intolerance of C. album to high concentration of KCl. In conclusion, C. album could tolerate high concentration of NaCl stress, accompanied by high ability to accumulate Na+ in leaves. These results could contribute to the further investigation of this promising species, e.g., amending saline soil.
