TITLE	Effects of ammonium, phosphate, and salinity on growth, gas exchange characteristics, and ionic contents of seedlings of mangrove Kandelia candel (L.) Druce.
AUTHOR	Yuan-Hsun Hwang* Institute of Botany, Academia Sinica, Taipei 115, Taiwan, Republic of China Shuh-Chun Chen Institute of Botany, Academia Sinica, Taipei 115, Taiwan, Republic of China
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ABSTRACT	The effects of ammonium, phosphate, and salinity on growth, gas exchange characteristics, and ionic content of seedlings of mangrove Kandelia candel (L.) Druce were investigated in solution culture experiments over seven months. High salinity at 20 ppt NaCl greatly reduced dry matter accumulation in shoots and roots and leaf CO2 assimilation rate. Addition of ammonium-nitrogen (2 mM) significantly increased the growth of shoots and roots, leaf CO2 assimilation rate, and respiration rate at low salinity treatments. Phosphate amendment alone did not affect the growth of plants. However, when ammonium-nitrogen was also added, phosphate improved the growth of plants, leaf CO2 assimilation rate, and respiration rate in low salinity treatments. Kandelia candel tended to maintain a constant cation concentration in tissues of leaves and roots at low salinity conditions. Potassium was the major cation in the tissues at the low salinity; however, it was replaced by sodium as the salinity of the culture solution was increased. Kandelia candel absorbed ammonium-nitrogen luxuriously at all salinity treatments and some of the ammonium accumulated in the tissues could be part of cations as the osmotic inorganic solute. Reasons for the difference in optimal growth salinity for K. candel between porewater in the field and the culture solution in the greenhouse are discussed.
KEYWORD	Ammonium; Growth; Kandelia candel; Mangrove; Nitrogen; Nutrients; Phosphate; Salinity;
ARTICLE INFO	Botanical Bulletin of Academia Sinica, Volume 42 Number 2 April 2001, page 131-139, 9 pages
PUBLISHER	Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan, Republic of China