EFFECTS OF NITROGEN CONCENTRATIONS ON PHOTOSYNTHESIS CHANGE OF LONGAN IN LYSIMETER

Authors:	C. Sritontip, Y. Khaosumain, S. Changjeraja
Keywords:	photosystem II (Fv/Fm), chlorophyll content, transpiration rate, stomata, conductance rate, CO₂ assimilation
Abstract: The experiment was conducted in order to determine the effects of nitrogen concentrations on leaf photosynthesis of longan on two-year old grafted 'Do' longan trees. The experiment was conducted at Lampang Agricultural Research and Training Center, Lampang during June 2003 - August 2004. The experimental design used was a CRD with five treatments, i.e. 0, 56, 112, 224 and 448 mg N L^-1 of nutrient solution modified from Hoagland and Arnon. The results showed that the 448, 224, 112 and 56 mg N L^-1 treatments from August 2003 to June 2004 gave higher efficiency of photosystem II (Fv/Fm) than the 0 mg N L-1 treatment (control). The 448 mg N L^-1 treatment had the highest change of chlorophyll content in leaf but the 0 mg N L^-1 treatment showed the lowest content. In addition, all treatments showed no difference in the change of transpiration rate or stomata conductance rate. The 448 mg N L^-1 treatment possessed the highest net CO₂ assimilation rate change during August - September 2003 and June 2004.
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