Vine Photosynthesis and Relationships to Climbing Mechanics in a Forest Understory

Photosynthesis in a deciduous forest understory was studied for three exotic vine species ( Pueraria lobata, Lonicera japonica , and Hedem helix ) and five common native species ( Rhus radicans, Clematis virginiana, Smilax rotundifolia, Vitis vulpina , and Parthenocissus quinquefolid ) possessing a variety of climbing mechanisms. The adventitious‐root climbers ( H. helix and R. radicans ) had the lowest maximum photosynthetic rates of all species (5.5 and 6.4 μ mol m –2 s –1 , respectively). The twining vine P. lobata was the most poorly adapted to the understory with a high light‐compensation point (43 μ mol m –2 s –1 ), low photosynthesis under low light (0.5 μ mol m 2 s –1 at 50 μ mol m –2 s –1 ), and the highest light requirement for obtaining 90% of maximum photosynthesis (860 μ mol m –2 s –1 ). Lonicera japonica , another twining vine, was better‐adapted to low light conditions, but vines with tendril climbing mechanics were physiologically the best adapted to low light. The adhesive‐tendril climber P. quinquefolia was the most highly adapted to shade, with a low light compensation point (20 μ mol m –2 s –1 ), a high photosynthetic rate under low light (3.5 μ mol m –2 s –1 ), and a low light saturation point (160 μ mol m –2 s –1 ). Results suggest that physiological adaptability of vines to low‐light environments may be related to climbing mechanics.