Abstract:

To explore the effects of different nitrogen supply levels on Dendrobium nobile growth, nutrient distribution and quality under greenhouse facility cultivation, so as to provide theoretical reference for its precise facility cultivation and quality control. Three-year-old plants of D. nobile were used as test materials. By measuring morphological indexes, flowering traits, and nitrogen (N), phosphorus (P) and potassium (K) content changes and dendrobine content in different periods and different parts of the plants, we investigated the effects on D. nobile growth and quality and the transfer and distribution of nutrient elements (N, P and K) in vivo under the different nitrogen supply levels (water control CK, 1/2N, 1N and 2N). The results showed that the growth trend of plants and the content changes of N, P and K under different nitrogen supply levels were basically the same. The dry matter weight of aboveground part increased gradually, and the effect of nitrogen application treatment was significantly better than that of the control, but the difference among different nitrogen supply treatments was not significant. There was a tendency of N to transfer from old stems to new stems in different periods. The P content in different parts of D. nobile increased first and then decreased. The K content of 1-year-old leaves was relatively high (35.91 g/kg), while that of 2- and 3-year-old stems was significantly lower than that of other parts. The ratio of nitrogen element in the aboveground part to that in the underground part increased significantly from April to June, and then gradually decreased, which was consistent with of nitrogen demand in the vegetative growth period. Although the phosphorus element ratio showed a significant downward trend, different nitrogen supply levels had no significant effect on the phosphorus element ratio. The potassium ratio was higher under low nitrogen supply levels. In terms of flowering quality, 1/2N and 1N treatments were better than other treatments. Nitrogen application helped to increase the content of dendrobine in plants, and the content of dendrobine in stems was significantly higher than that in leaves and roots. The content of dendrobine in non-annual stems decreased with the increase of nitrogen supply level, but the opposite was observed in annual stems, leaves and roots. There was no significant difference in the content of dendrobine among stems of different years. Among different parts of the plant, the active annual leaves and stems had higher N, P and K contents, and the older stems had lower contents, indicating that nutrients were preferentially transferred to young tissues to meet the needs of growth. In the vegetative growth period, the demand for N, P and K was relatively high, and in the reproductive period, the demand gradually decreased, reaching the lowest in the flowering period of the next year. During the transition period from vegetative growth to reproductive growth, appropriately increasing the application amount of phosphorus fertilizer could promote the expansion and maturation of pseudobulbs. In the reproductive growth period, to increase the application of potassium fertilizer was beneficial to the accumulation of nutrients, and the application of nitrogen was helpful to increase the content of dendrobine and improve the medicinal quality, while the low nitrogen treatment was beneficial to improve the flowering quality.

Key words: Dendrobium nobile, facility cultivation, nitrogen, dendrobine, transfer