Plukenetia volubilis, a tropical evergreen liana native to South America, is a promising new oilseed crop species belonging to the family Euphorbiaceae. Currently, the analysis of the impact of regulated deficit irrigation（RDI）and fertilization on the agronomic traits of P. volubilis plants has been limited.
Researchers from Xishuangbanna Tropical Botanical Garden (XTBG) conducted a study to test how seedlings (vegetative) and large plants (reproductive) of Plukenetia volubilis responded to regulated deficit irrigation techniques (conventional deficit irrigation, DI; alternative partial root-zone irrigation, APRI) in a tropical humid monsoon area.
In response to water deficit, the high sensitivity of seedling growth was attributed to the great reduction in leaf area and photosynthetic rate, whereas the growth of the large field-grown P. volubilis plants at the reproductive stage had a low sensitivity.
The fast growth in vegetative seedlings of P. volubilis plants can be achieved by irrigation applied to meet full evapotranspiration at the cost of whole-plant water-use efficiency, because both APRI and DI significantly reduced their normal growth.
Compared with DI at the same amount of irrigation, APRI was more efficient in improving the whole-plant water-use efficiency of the vegetative seedlings and the irrigated water-use efficiency of large reproductive plants.
The total seed oil yield of P. volubilis plants was largely determined by the seed (fruit) numbers per unit area, rather than by seed size or seed oil concentration, across irrigation and fertilization treatments.
The magnitude of increase in total seed and seed oil yield by fertilization was similar among different irrigation regimes, as no interactions of irrigation × fertilization were found.
Carbon storage may be an active process, occurring at the expense of growth, whereas C and N shortages are essential for the yield formation under drought.