Effects of drought and nitrogen application on the growth and chlorophyll fluorescence characteristics of Dalbergia odorifera T. Chen - Hevea brasiliensis Muell. Arg seedlings

Dalbergia odorifera T. Chen and Hevea brasiliensis Muell. Arg were used to explore the effects of drought and nitrogen application on the growth, chlorophyll fluorescence characteristics, and interaction effects of the seedlings. Results showed that under the same nitrogen level, drought stress significantly increased the fluorescence parameters F_o and NPQ of the seedlings, but decreased plant height, basal diameter, leaf length, total chlorophyll, F_v/F_o, F_v/F_m, and ETR. Under the same water level, plants in the nitrogen application group exhibited better growth performance, and the promotion effects on D. odorifera were stronger than that on H. brasiliensis. Combined drought treatment and nitrogen application significantly affected the number of branches in D. odorifera and plant height increment, petiole length, chlorophyll a content, total chlorophyll content, and carotenoid content in H. brasiliensis. Mixed planting promoted the growth and development of D. odorifera and H. brasiliensis under humid conditions, while D. odorifera significantly inhibited the growth and photosynthetic performance of H. brasiliensis under drought conditions. These results showed that nitrogen application could alleviate the adverse effects of drought stress on the two species, and plant growth and photosynthetic pigment accumulation showed the best performance under nitrogen application in well-water. In addition, variations in soil moisture could change the interaction effects between D. odorifera and H. brasiliensis.