Kaolin, boron, and zinc increase photosynthetic activity and mitigate the effects of light stress in heliconia grown under semi-arid conditions

Abstract

Tropical flowers species of high commercial importance such as heliconia, if grown in semi-arid regions, can have their photosynthesis compromised and, consequently, flower production, due to high irradiation. Foliar applications of kaolin and the mineral nutrients boron and zinc may be an alternative for reducing the harmful effects of light stress. Thus, the objective of this study was to evaluate the effects of the application of these mitigating substances on physiological aspects in two species of heliconia grown under semi-arid conditions. The experimental design was randomized blocks in split-plot scheme, with four repetitions and four plants per replication. The plots consisted of two species of heliconias (H. psittacorum cv. Red Opal and H. bihai cv. Lobster Claw Two) and the subplots corresponded to three light stress mitigating substances (kaolin, boron + zinc, and control). The species H. psittacorum showed higher chlorophyll indexes, photosynthesis rate, stomatal conductance, and transpiration rate than the species H. bihai. The applications of kaolin and the mineral nutrients boron + zinc caused increases in the chlorophyll a and total chlorophyll indices, photosynthesis rate, carboxylation efficiency, effective quantum yield of photosystem II, leaf temperature, and vapor pressure deficit in plants of H. bihai and H. psittacorum. It is concluded that the foliar application of kaolin and the minerals boron and zinc reduce the harmful effects caused by high luminosity, with emphasis on the kaolin particle film, which promoted better photosynthetic performance and reduced the effects of non-stomatic limitation of photosynthesis, being a promising strategy for the cultivation of heliconia in semi-arid conditions. In addition, both kaolin and the minerals boron and zinc promote the production of flowering stems of heliconia with better quality and post-harvest durability.