Vanilla planifolia is a neotropical orchid, whose fruits produce the natural vanilla, a fundamental ingredient for the food and cosmetic industry. Because of its importance in the world market, it is cultivated in many tropical countries and recently its cultivation has started in Colombia. This species requires shade for its development; however, the optimal of light conditions are unknown. This work evaluates the effect of different light intensities on CAM photosynthesis, physiology, morphology, and growth of this species. For this, vanilla seedlings were subjected to four treatments of relative illumination (RI) (T1=8%, T2=17%, T3=31% and T4=67%). Most CO2 assimilation occurred along night in all treatments, which confirms that vanilla is a strong CAM species. Plants grown under high lighting (67% RI) had almost half of the photosynthesis in treatments of intermediate lighting (17 and 31%), which is consistent with the lower nocturnal acid accumulation in that treatment. Likewise, the photochemical efficiency of photosystem II (Fv / Fm) showed that in plants of the 67% RI occurred high radiation stress. On the other hand, vanilla plants reached greater length, leaf area, and total biomass when grown under intermediate radiation (17 and 31% RI). These results suggest that high radiation alters the functioning of vanilla plants, inhibiting photosynthesis and growth, and that highly shaded environments not significantly affected the CAM photosynthesis of vanilla; however, in the long-term this species showed higher photosynthesis and growth under intermediate levels of radiation
In the Amazon region, agroforestry systems (AFSs) are recommended as a sustainable production alternative for local communities. A common component in Amazonian AFSs are tropical fruit trees, which can form the canopy or grow in the understory. In this study, we evaluated the effect of high radiation on photosynthesis, growth and seedling survival of four Amazonian fruit-tree species: Theobroma cacao, Eugenia stipitata, Inga edulis and Psidium guajava. Growth, chlorophyll fluorescence, gas exchange, and leaf pigments were measured in seedlings of each species grown for 12 months inside shade houses with low (8%), medium (30%) and high relative illumination (100%). Eugenia stipitata and T. cacao had the lowest acclimation capacity to high solar radiation, followed by I. edulis. Therefore, these species must be grown under intermediate light levels in early growth stages, to protect them from direct sunlight. In contrast, P. guajava seedlings demonstrated high tolerance to elevated radiation, therefore, this species can be planted under full sunlight.
Nutritional status affects the processes of flowering and fruiting of plants. This study was conducted to determine the effects of fertilizer application on flowering, fruiting, and leaf nutrient content of Vanilla planifolia Jacks. ex Andr. Treatments consisted of the application of grade 10-20-20 nitrogen, phosphorus and potassium (NPK) fertilizer to the substratum in annual doses of 20, 50 and 100 g/plant plus a monthly application of foliar fertilizer. Two more treatments were foliar fertilization and a control (no fertilization). Treatments increased the number of inflorescences and flower buds per plant, as well as the number and weight of fruits per plant, and decreased the abortion of flowers and immature fruits. These effects depended on Downloaded by [University of Nebraska, Lincoln] at 13:03 07 October 2015 ACCEPTED MANUSCRIPT ACCEPTED MANUSCRIPT 2 the type of fertilizer, the amount applied, and the time of evaluation. The best results were obtained with the 100 g/plant-year treatment with an annual production of 1.5 kg of fruits per plant in the second year. Unfertilized plants produced 0.55 kg/plant-year. Differences were alsofound in foliar content of N, P, K, and copper (Cu) between vegetative and reproductive branches. Application of fertilizer to the substratum appears to improve reproductive parameters of vanilla plants and the production of beans, while foliar fertilization alone was ineffective in increasing crop productivity. Nutrients also seem to translocate from mature leaves to fruit racemes.
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