Terrestrial environment

Effects of elevated CO2 concentration on growth and water usage of tomatoseedlings under different ammonium/nitrate ratios


LI Juan , ZHOU Jian-min , DUAN Zeng-qiang

DOI:

Received November 11, 2006,Revised March 21, 2007, Accepted , Available online

Volume 19,2007,Pages 1100-1107

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Increasing atmospheric CO2 concentration is generally expected to enhance photosynthesis and growth of agricultural C3 vegetable crops, and therefore results in an increase in crop yield. However, little is known about the combined e ect of elevated CO2 and N species on plant growth and development. Two growth-chamber experiments were conducted to determine the e ects of NH4 +/NO3?? ratio and elevated CO2 concentration on the physiological development and water use of tomato seedlings. Tomato was grown for 45 d in containers with nutrient solutions varying in NH4 +/NO3- ratios and CO2 concentrations in growth chambers. Results showed that plant height, stem thickness, total dry weight, dry weight of the leaves, stems and roots, G value (total plant dry weight/seedling days), chlorophyll content, photosynthetic rate, leaf-level and whole plant-level water use e ciency and cumulative water consumption of tomato seedlings were increased with increasing proportion of NO3- in nutrient solutions in the elevated CO21 treatment. Plant biomass, plant height, stem thickness and photosynthetic rate were 67%, 22%, 24% and 55% higher at elevated CO2 concentration than at ambient CO2 concentration, depending on the values of NH4+/NO3- ratio. These results indicated that elevating CO2 concentration did not mitigate the adverse e ects of 100% NH4 +-N (in nutrient solution) on the tomato seedlings. At both CO2 levels, NH4 +/NO3- ratios of nutrient solutions strongly influenced almost every measure of plant performance, and nitrate-fed plants attained a greater biomass production, as compared to ammonium-fed plants. These phenomena seem to be related to the coordinated regulation of photosynthetic rate and cumulative water consumption of tomato seedlings.

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