Effects of rejuvenation of root-sprout on leaf morphology, nutrients and photosynthetic physiology of Robinia pseudoacacia cuttings

The aim of this experiment was to explore the effects of root sprouting rejuvenation on the growth of Robinia pseudoacacia cutting seedlings, and provide a theoretical basis for the establishment of Robinia pseudoacacia rejuvenation system in the future production practice.

The cuttings of Robinia pseudoacacia root sprouts and semi-lignified branches of the mother tree were used as propagation materials, and the 1-year-old seedlings of Robinia pseudoacacia were set as the control. The differences in leaf morphology and anatomical structure, dry and fresh weight, gas exchange parameters, chlorophyll fluorescence parameters, photosynthetic enzyme activity and nutrient physiology of seedlings cultivated with different propagation materials were determined.

The results showed that, compared with the seedlings and mother tree branch cuttings, the root sprouting and rejuvenation treatment significantly increased the leaf length, leaf width, leaf perimeter, leaf area, dry and fresh weight, and leaf axis length of Robinia pseudoacacia cuttings, and significantly reduced the thickness of the upper epidermis, palisade tissue, and leaf thickness. Compared with seeded seedlings, the thickness of spongy tissue, leaf compactness, leaf porosity and the P/S ratio had no significant changes. The content of photosynthetic pigment, net photosynthetic rate, transpiration rate, F_v/F_m, F_v/F_o, NPQ and other gas exchange parameters, chlorophyll fluorescence parameters of Robinia pseudoacacia seedlings were significantly increased by root sprouting and rejuvenation treatment, and the rooting sprouts in one year were the highest. The activities of fructose 1,6-bisphosphate aldolase (FBA) and ribulose-1,5-diphosphate carboxylase/oxygenase (Rubisco) in the seedlings after root sprouting and rejuvenation were significantly higher than those in the mother branch cuttings, but there were still significant differences between the seedlings and the seedlings; However, the C/N, N/P, NSC and starch contents as well as the dry and fresh weight of leaves increased. The seedlings after root sprouting and rejuvenation had higher nutrient utilization efficiency and dry matter accumulation, and the one-year-old rooting shoots was the highest.

The cuttings of Robinia pseudoacacia, which have been rejuvenated by root sprouting, have stronger growth potential and juvenility, which provides theoretical support for the breeding of improved varieties and strong seedlings of Robinia pseudoacacia.