Journal of Food, Agriculture and Environment

Effects of potassium fertilizer application on photosynthesis and seedling growth of sweet potato under drought stress

Author(s):

L. D. Zhu ^{1, 2, 3}, X. H. Shao ^{1, 2}, Y. C. Zhang ³*, H. Zhang ^{3, 4}, M. M. Hou ^{1, 2}

Recieved Date: 2012-05-27, Accepted Date: 2012-10-02

Abstract:

The pot experiment was carried out to study the dry matter accumulation and the photosynthesis of sweet potato with three different potassium levels (K₂O  0, 150 and 300 mg per kg air-dried soil) under the drought condition (50% field capacity). The results showed that the drought stress decreased the biomass accumulation of sweet potato leaves and petioles significantly, while the biomass of the roots increased slightly, and the water use efficiency of leaf (WUEi) of sweet potato was promoted dramatically. Meanwhile, the dry matter accumulation of leaves, petioles and the total biomass decreased remarkably with a higher potassium fertilization, but there was no obvious change on the biomass of leaves and petioles, the WUEi of the sweet potato under K150 was much higher than those of non-potassium and K300 fertilization. Under the drought condition, the leaf photosynthesis of sweet potato was limited mainly by the stomatal factors, parameters such as net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs) and intercellular carbon dioxide concentration (Ci) declined significantly, and stomatal limitation value (Ls) and WUEi increased significantly. Gs, Tr and Ci increased dramatically while Ls and WUEi decreased with a potassium fertilization of K150~K300, suggesting the stomatal effects were lightened. There was no obvious change on the leaf Rubisco activities and the content of chl a, chl b and chl of sweet potato under K150 fertilization, however, these indexes decreased significantly with the potassium supply of K300, and the photosynthesis of sweet potato was limited by non-stomatal factors under this circumstance. It was summed that the drought stress limited the photosynthesis of sweet potato by stomatal factors, which would also reduce the biomass accumulation of sweet potato. The stomatal effects were lightened by potassium application with the WUEi of leaves decreased but the water productivity increased obviously, since higher potassium application could cause the non-stomatal limitation to photosynthesis. Therefore, in the potassium fertilization management of sweet potato, the fertilizing amount should be appropriate based on the actual situation. 

Keywords:

Sweet potato, seedling growth, photosynthetic parameters, Rubisco activity, photosynthetic pigments

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Journal: Journal of Food, Agriculture and Environment
Year: 2012
Volume: 10
Issue: 3&4
Category: Agriculture
Pages: 487-491

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