Effect of elevated CO 2 on vegetative and reproductive growth characteristics of the CAM plants Hylocereus undatus and Selenicereus megalanthus

Abstract

This study examined the vegetative and reproductive growth responses of the crassulacean acid metabolism (CAM) vine-cactus fruit crop species Hylocereus undatus and Selenicereus megalanthus to CO 2 enrichment (1000 μmol mol −1 vs. control of 380 μmol mol −1). H. undatus plants enriched with CO 2 demonstrated 52%, 22%, 18%, and 175% increases, relative to plants measured in ambient CO 2, in total daily net CO 2 uptake, shoot elongation, shoot dry mass, and number of reproductive buds, respectively. The responses of S. megalanthus plants exposed to elevated CO 2 were greater than those of H. undatus under the same conditions. Compared to plant responses in ambient CO 2, under conditions of CO 2 enrichment, S. megalanthus showed 129%, 73%, 68%, and 233% increases in total daily net CO 2 uptake, shoot elongation, shoot dry mass, and number of reproductive buds, respectively. Moreover, for H. undatus, there was no significant change in fruit fresh mass although it showed a slight (7%) upward trend. On the other hand, fruit fresh mass of S. megalanthus significantly increased by 63% in response to elevated CO 2. These results indicate the high potential of CAM plants to respond to CO 2 enrichment. It is thus apparent that S. megalanthus grown under CO 2 enrichment may benefit from elevated CO 2 to a greater extent than H. undatus grown under sub-optimal growth conditions.