The role of cotyledons in the establishment of Suaeda physophora seedlings

Abstract

The role of cotyledons in seedling establishment of the euhalophyte Suaeda physophora under non-saline and saline conditions (addition of 1 mM or 400 mM NaCl) was investigated. Survival and fresh and dry weights were greater for seedlings grown in the light (12-h light/12-h dark) than in the dark (24-h dark). The shading of cotyledons tended to decrease shoot height, shoot organic dry weight, number of leaves, and survival of seedlings regardless of NaCl treatment, but the effect of cotyledon shading was greater with 400 mM NaCl. Concentrations of Na⁺ were higher in cotyledons than in leaves, regardless of NaCl treatment. The K⁺/Na⁺ ratio was lower in cotyledons than in leaves for seedlings treated with 1 mM NaCl but not for seedlings treated with 400 mM NaCl. Addition of 400 mM NaCl decreased oxygen production in cotyledons but especially in leaves. These results are consistent with the hypothesis that, by generating oxygen via photosynthesis and by compartmentalizing Na⁺, cotyledons are crucial for the establishment of S. physophora seedlings in saline environments.

Keywords::

• Halophyte
• ion compartmentalization
• oxygen evolution
• salinity
• salt tolerance

Acknowledgements

We thank Dr Mustapha Gorai for his critical reading and revision of the manuscript. The financial support from the Natural Science Research Foundation of Shandong Province (ZR2010CM005), the Special Fund for Agriculture Profession of China (200903001-03-03), the Special Fund for Agro-scientific Research in the Public Interest (201103007), and the West Light Foundation of the Chinese Academy of Science (XBBS200802) are also greatly appreciated.

Notes

^* These authors equally contributed to this work.