Response of growth and physiological characteristics of three Magnolia spp. seedlings to drought stress

Objective This study investigated the effects of drought stress on growth and physiological changes of Magnolia sieboldii, M. biondii, M. wufengensis ‘Jiaohong No.2’ to explore the influence mechanism of drought stress on three Magnolia spp. seedlings, evaluate the drought resistance of Magnolia spp. seedlings, and provide a basis for the introduction and promotion of seeds in arid areas.

Method The 2-year-old potted seedlings of 3 kinds of Magnolia spp. seedlings were used as experimental materials, 4 treatment levels (SWC80%−90% (CK), 60%−70% (T₁), 40%−50% (T₂), 20%−30% (T₃)) were set, and the changes of 19 indexes, including growth and physiology were analyzed after 50 d of drought stress.

Result (1) Moderate and severe drought stress (T₂, T₃) significantly decreased the ground diameter increment and biomass increment of 3 kinds of Magnolia spp. seedlings, and significantly increased the root-shoot ratio of M. biondii and M. wufengensis ‘Jiaohong No.2’(P < 0.05). Under severe drought stress (T₃), the increment of plant height and biomass of M. wufengensis ‘Jiaohong No.2’ was significantly higher than that of M. biondii (P < 0.05). (2) Compared with CK, T₁ increased the chlorophyll contents of M. wufengensis ‘Jiaohong No.2’, and the content of chlorophyll in the 3 kinds of Magnolia spp. seedlings gradually decreased at other drought levels. With the intensification of drought, the content of malondialdehyde, soluble sugar, soluble protein and the activity of superoxide dismutase, catalase of the 3 kinds of Magnolia spp. seedlings gradually increased, and T₃ and CK showed significant differences. Proline content of M. biondii decreased first and then increased, and the proline content of M. sieboldii and M. wufengensis ‘Jiaohong No.2’ showed an increasing trend with the intensification of drought. The peroxidase activity of 3 kinds of Magnolia spp. seedlings varied with the intensities of drought. The peroxidase activity of M. sieboldii was the highest at T₂, and those of M. biondii and M. wufengensis ‘Jiaohong No.2’ were the highest at T₃. (3) The net photosynthetic rate, intercellular CO₂ concentration and transpiration rate of M. wufengensis ‘Jiaohong No.2’ were the highest at T₁, which were 2.67%, 1.94% and 3.09% higher than CK, respectively. The stomatal conductivity and water use efficiency decreased gradually with the worsening of drought. Severe drought stress (T₃) significantly reduced the net photosynthetic rate, intercellular CO₂ concentration, transpiration rate, stomatal conductivity and water use efficiency (P < 0.05) of M. sieboldii and M. biondii. (4) The analysis of membership function showed that the drought resistance of 3 kinds of Magnolia spp. seedlings was M. sieboldii > M. wufengensis ‘Jiaohong No.2’ > M. biondii.

Conclusion Drought stress affects the growth and physiological activities of the 3 kinds of Magnolia spp. seedlings, damages the leaf cell structure and slows plant growth, but the plants could resist drought and maintain their normal physiological metabolic functions by adjusting their own osmoregulatory substance content and protective enzyme activities. Based on the indicators, the drought resistance of M. sieboldii is the strongest, and the drought resistance of M. biondii is the weakest.