Leaf Photosynthesis, Growth, and Seed Chemicals of Sacha Inchi Plants Cultivated Along an Altitude Gradient

Sacha inchi (Plukenetia volubilis L.) is known to naturally grow under a wide range of elevational gradients in South America. We assessed the combined effects of altitude (560, 900, 1200, and 1490 m asl) and season on leaf- and whole-plant traits and seed chemicals of sacha inchi plants in Xishuangbanna, Southwest China, to explore the optimum altitudinal zone for its cultivation. Leaf maximum net photosynthetic rate (A(max)), stomatal conductance (g(s)), and dark respiration (R-d) were greatest in the wet season and lowest in the cool season. With similar values in the wet season between altitudes, the reduction in A(max) and g(s) was greater in plants growing in higher elevations than in lower elevations in the cool season. Plant biomass and fruit production were highest at lower altitudes and dramatically decreased above 900 m, which can primarily be attributed to a C source limitation. Sacha inchi could be useful for cropping in cooler regions because the reproductive growth is adapted to high elevations. The oil and protein content and linolenic and unsaturated fatty acid (UFA) concentrations in seeds were highest in the cool season. With an increase in elevation, the linolenic and UFA concentrations in seeds increased. We concluded that lower altitudes (<900 m) could be the optimum zone for growth and yield of sacha inchi plants whereas seeds collected from plants growing at higher altitudes (>900 m) and in the cool season appear to have better quality.