Light deficiency and waterlogging affect chlorophyll metabolism and photosynthesis in Magnolia sinostellata
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In Magnolia sinostellata plants grown under shading and waterlogging conditions, solar noon PFD level of 1050 ± 30 µmol·m− 2·s− 1 and running water combined treatment (L1W2) triggers changes in chlorophyll metabolism and photosynthesis, which benefits growth of this endangered species.
Magnolias are widely used as ornamental plants in cities, but they are facing extinction in the wild. It has been hypothesized that shading from trees in the upper canopy and stress from waterlogging conditions reduce their survival rates. To test this hypothesis, we grew 2-year-old Magnolia sinostellata seedlings either under natural light level (solar noon PFD of 1400 ± 28 µmol·m− 2·s− 1) and normal watering conditions (watered every 3 days) (control, CK) or reduced light levels (L1 1050 ± 30 µmol·m− 2·s− 1; L2 700 ± 27 µmol·m− 2·s− 1 and L3 490 ± 25 µmol·m− 2·s− 1) in combination with two types of waterlogging scenarios: still water treatment (W1, water level kept at 2 cm above soil surface) or running water treatment (W2, constantly irrigated via drip-irrigation). Measurements of chlorophyll content, gas exchange, and relative expression of genes involved in chlorophyll synthesis revealed that chlorophyll content, net photosynthetic rate, stomatal conductance, and transpiration rate were significantly higher in L1W2 treatment than the control or any of the other treatment examined, whereas the intercellular CO2 concentration was lower under the L1W2 treatment. The expression levels of genes involved in chlorophyll biosynthesis were higher under L1W2 than CK conditions, but lower under L1W1, L2W1, L2W2, L3W1, and L3W2 treatment. These results suggest that L1W2 condition is most suitable for chlorophyll synthesis and photosynthesis of M. sinostellata. This study provides new insights into the physiology and development of endangered plants and useful guidance for conservation efforts aimed at protecting wild magnolia species.
KeywordsMagnolia sinostellata Chlorophyll Photosynthesis Shading and water treatments
We are thankful to the editor and two anonymous reviewers for their comments on this paper. We thank Lailiang Cheng (Department of Horticulture, Cornell University, USA) for careful advising of this article. We thank Dr. Bin Dong, Chao Zhang for sharing knowledge about gene sequence analysis. This work was financially supported by the National Natural Science Foundation of China (31400599); the 13th 5-Year-Plan for Floriculture Special Breeding of Zhejiang Province, China (2016C02056-12); and the Public Welfare Forestry Industry Project of State Forestry Administration, China (201504322).
Author contribution statement
QY and YS were the equal chief scientist in this study, designed the experiments, conducted statistical analysis, and wrote the manuscript; QW, XW and LF, major participants in this study, were responsible for data collection; YW, SZ, ZL and MZ, major participants in this study, were responsible for manuscript revision and language improvement.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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