Abstract:

Objective: Both Dinochloa orenuda and Bonia levigata are climbing bamboos distributed in the tropical lowland rainforest of Hainan Island. The former species is a heliophiles distributed in forest edges and forest gaps while the latter one is a skiophyte in the low light environment. This paper aimed to explore the survival strategies of the two bamboo species in the tropical lowland rainforest, so as to provide a knowledge for the protection and utilization of climbing bamboo resources. Method: D. orenuda and B. levigata were sampled from Ganshiling, Hainan Island in June, September, December 2019, and March 2020. The leaf anatomical structure, leaf gas exchange parameters, leaf area, leaf dry-matter content, and specific leaf area were studied by using paraffin section, leaf epidermis isolation, and LI-6400 portable photosynthesis system, respectively. Result: 1) The net photosynthetic rate (P_n), stomatal conductance (Cond), intercellular carbon dioxide concentration (C_i), and transpiration rate (Tr) of D. orenuda were higher in June and September than those in December. In contrast to these characteristics, the water use efficiency (WUE) of D. orenuda had an opposite trend in these months. The net photosynthetic rate, stomatal conductance, intercellular carbon dioxide concentration, and transpiration rate of B. levigata were the highest in September and lower in March and June, but water use efficiency was the highest in March and the lowest in September. Except for the intercellular carbon dioxide concentration in December, the net photosynthetic rate, stomatal conductance, intercellular carbon dioxide concentration, and transpiration rate of D. orenuda were higher than those of B. levigata in each month, respectively. 2) The leaf thickness (LT), number of bulliform cells (NBC), sectional area of bulliform cells (SABC), diameter of second-order vascular bundle (DSVB), sectional area of second-order vascular bundle (SASVB), distance between second-order vascular bundle (DBAVB), and percent of stomata area (AP) of the two bamboos were the higher in the rainy season (June, September) than those in the dry season (December, March). Besides, the LT, stomata width (SW), single stomata area (AS), and AP of D. orenuda were higher than those of B. levigata in each month. Whereas the mastoid process thickness (MPT), upper epidermal thickness (UET), DBAVB, and stomata density(SD) of D. orenuda were lower than those of B. levigata in the same time periods, respectively. 3) There were significant differences (P < 0.05) in the maximum and minimum of single leaf area (LA), leaf dry-matter content (LDMC), and specific leaf area (SLA) between D. orenuda and B. levigata in each month, but there was no significant difference(P > 0.05) in SLA between D. orenuda and B. levigata. 4) The plasticity of various indicators of D. orenuda was higher than that of B. levigata, which reflected that D. orenuda had higher adaptability to the environment than B. levigata. Conclusion: With its relatively large photosynthetic capacity, LT, AS, and relatively lower LA, SLA, and DBAVB, D. orenuda can adapt to forest canopy strong light environment, canopy water deficit, and dry season stress. However, B. levigata can adapt to drought stress and weak light environment under the forest with higher LA, SLA, UET, and MPT, thinner leaf thickness, and small and dense stomata. Our results have revealed that the functional traits of leaves determine different survival and adaptive strategies of the two climbing bamboos.

Key words: climbing bamboo, leaf anatomy, photosynthetic characteristics, leaf functional traits