Objective The aims of the study are to explore the relationship between water-carbon metabolism and growth and fruiting of different angle branches of Hippophae rhamnoides subsp. sinensis Rousi, deeply understand the impact of branch angle on water-carbon metabolism and growth and fruiting, as well as its intrinsic physiological mechanisms, and provide a theoretical basis for the formulation of efficient cultivation techniques for seabuckthorn.

Method Based on the four angle branches(0°, 45°, 90°, and 135°) of Hippophae rhamnoides subsp. sinensis Rousi, the differences in water status, photosynthesis, non-structural carbohydrate (NSC) content, branch and leaf buds growth status, fruiting traits, and fruit nutritional components of different angle branches were compared, and the relationship between water-carbon metabolism and growth and fruiting of different angle branches was analyzed.

Result There was no significant difference in the water potential between 0°-90° branches in July. The water potential of 135° branches in the early morning and noon of July was significantly lower than other angles. With the increase of branch angle, the PLC of branches in July and September showed an increasing trend, while the specific leaf area hydraulic conductivity and the specific stem area hydraulic conductivity of branches showed a decreasing trend. The difference in net photosynthetic rate between 0°-90° branches was not significant, while the net photosynthetic rate of 135° branches was significantly lower than other angles. There was no significant difference in NSC content in branches in July, but the NSC content in the xylem of branches increased first and then decreased. The NSC content in the phloem of branches decreased with the increase of branch angle in September. Leaf area and growth of new shoots decreased with the increase of branch angle. While specific leaf weight, total number of new shoots, flower bud proportion, flower bud longitudinal and transverse diameter, fruit longitudinal and transverse diameter and 100-fruit weight, number of fruits per 10 cm and total flavonoids content incerased first and then decreased, reaching a higher level at 45° and 90°.

Conclusion With the increase of branch angle, the water condition during drought period and the nutritional growth of branches deteriorates. The NSC storage, flower bud differentiation, and fruiting traits perform better at 45°-90°. This indicates that water-carbon metabolism is an important pathway for the influence of branch angle on the growth and fruiting characteristics of seabuckthorn. The utilizing of 45°-90° branches can promote yield formation in production.