Light deficiency and waterlogging affect chlorophyll metabolism and photosynthesis in Magnolia sinostellata

Key message 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 (L 1 W 2 ) 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 seedlin gs 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 (L 1 1050 ± 30 µmol·m − 2 ·s − 1 ; L 2 700 ± 27 µmol·m − 2 ·s − 1 and L 3 490 ± 25 µmol·m − 2 ·s − 1 ) in combination with two types of waterlogging scenarios: still water treatment (W 1 , water level kept at 2 cm above soil surface) or running water treatment (W 2 , 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 L 1 W 2 treatment than the control or any of the other treatment examined, whereas the intercellular CO 2 concentration was lower under the L 1 W 2 treatment. The expression levels of genes involved in chlorophyll biosynthesis were higher under L 1 W 2 than CK conditions, but lower under L 1 W 1 , L 2 W 1 , L 2 W 2 , L 3 W 1 , and L 3 W 2 treatment. These results suggest that L 1 W 2 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.