Microclimate changes, photomorphogenesis and water consumption of Moringa oleifera cuttings under different light spectrums and exogenous phytohormone concentrations

Abstract

Moringa oleifera is one of the most important plants in the world due to its multiple uses as well tolerance to abiotic stress. However, it may presents low quality seedlings in protected environment under thermal and luminous stresses. The current study aimed to evaluate environmental microclimate changes; photomorphogenesis and water use of M. oleifera cuttings under light spectral and phytohormones variations, as well as to identify the most important variables to explain those effects. A completely randomized experimental design was used in a 4 x 4 factorial design with four replications. Four luminosity conditions, white (a transparent plastic layer), blue (two layers of blue cellophane paper), red (two layers of red cellophane paper), and extreme red lights (one layer of red cellophane and one of alternating blue cellophane) and four phytohormones concentrations (0, 25, 50, and 100%) were applied. M. oleifera semi-woody cuttings were collected from 7 am to 9 am from the M. oleifera mother plants, grown on a rural property located in the city of Lagoa Seca, Paraíba, Brazil, with the following characteristics: 15 cm in length, 4 to 5 mm in diameter, and 2 or 3 buds. Throughout the experimental period, environments were monitored to determine illuminance, average air temperature, relative humidity, soil average temperature, and evapotranspirated water consumption by cuttings. The numbers of shoots were recorded weekly. The number of surviving roots and shoots were measured 60 days after M. oleifera cuttings planting. Illuminance was reduced in environments under blue, red, and extreme red lights, respectively. The air temperature was reduced under blue light, while red and extreme red lights induced the increase on air temperature and relative humidity, soil temperature, and therefore, water consumption of cuttings. Protected environments when irradiated with blue light and application of phytohormones at concentrations of 25 and 50% enabled the shootings and survival of cuttings, although no root formation was observed after 60 days from planting. All variables were considered important to explain the effects.