Articles
EFFECTS OF 5-AMINOLEVULINIC ACID (ALA) ON PHOTOSYNTHESIS AND CHLOROPHYLL FLUORESCENCE OF WATERMELON SEEDLINGS GROWN UNDER LOW LIGHT AND LOW TEMPERATURE CONDITIONS
Article number
856_21
Pages
159 – 166
Language
English
Abstract
The effects of 5-aminolevulinic acid (ALA) with concentrations 50-200 mg/L on the photosynthesis and chlorophyll fluorescence characteristics of watermelon (Citrullus × lanatus Thunb.
Mansfeld) seedlings grown in a growth chamber, where the day/night temperatures were about 20/10°C and the maximum light intensity was about 600 μmol m-2 s-1 at the top of plants, lower than the requirements for vigorous growth of the species, were studied and the main results are as follows. (1) The dry weights of the plants after ALA treatment for one month were more than 50% greater than that of the control, suggesting that ALA treatment might regulate assimilatory accumulation under low light and chilling stresses. (2) The net photosynthetic rates (Pn) of the treated plants were about 34-44% higher than that of the control. (3) The soluble sugar content of the treated plant leaves was about 32-87% higher and the starch content of the treated was about 70-227% higher than that of the control. (4) ALA treatments decreased the minimum fluorescence (Fo), and increased the maximum fluorescence (Fm), resulting in higher levels of the maximum photochemical efficiency (Fv/Fm) of the dark adapted leaves.
ALA treatments also increased the actual photochemical efficiency of the photosystem (
PSII), electronic transfer rates (ETR), photochemical quench (qP) and non-photochemical quench (NPQ) in light adapted leaves.
Thus, the photon energy irradiated on watermelon leaves was more easily harvested by PSII and then transformed into bioelectric energy in the reaction centre and transferred in the photosynthetic electronic chains in the ALA-treated plants.
The increase of NPQ induced by ALA might be a protective mechanism against photo-injury during photosynthesis.
These results suggested that ALA might be used to improve the tolerance of watermelon to low light and chilling stress.
Mansfeld) seedlings grown in a growth chamber, where the day/night temperatures were about 20/10°C and the maximum light intensity was about 600 μmol m-2 s-1 at the top of plants, lower than the requirements for vigorous growth of the species, were studied and the main results are as follows. (1) The dry weights of the plants after ALA treatment for one month were more than 50% greater than that of the control, suggesting that ALA treatment might regulate assimilatory accumulation under low light and chilling stresses. (2) The net photosynthetic rates (Pn) of the treated plants were about 34-44% higher than that of the control. (3) The soluble sugar content of the treated plant leaves was about 32-87% higher and the starch content of the treated was about 70-227% higher than that of the control. (4) ALA treatments decreased the minimum fluorescence (Fo), and increased the maximum fluorescence (Fm), resulting in higher levels of the maximum photochemical efficiency (Fv/Fm) of the dark adapted leaves.
ALA treatments also increased the actual photochemical efficiency of the photosystem (
PSII), electronic transfer rates (ETR), photochemical quench (qP) and non-photochemical quench (NPQ) in light adapted leaves.Thus, the photon energy irradiated on watermelon leaves was more easily harvested by PSII and then transformed into bioelectric energy in the reaction centre and transferred in the photosynthetic electronic chains in the ALA-treated plants.
The increase of NPQ induced by ALA might be a protective mechanism against photo-injury during photosynthesis.
These results suggested that ALA might be used to improve the tolerance of watermelon to low light and chilling stress.
Authors
L.J. Wang, Y.P. Sun, Z.P. Zhang, L. Kang
Keywords
5-aminolevulinic acid, carbohydrate, chlorophyll fluorescence, low light and chilling stresses, photosynthesis, watermelon
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