BONOU, S. I.; http://lattes.cnpq.br/0278611065117108; BONOU, Semako Ibrahim.
Résumé:
The population increase associated with the exploitation of natural resources and
climate change influences the demand for food, especially in semi-arid regions, which
highlights the need for technologies for better adaptation of cultivated species. In this
perspective, the objective was to induce tolerance to stresses caused by water deficit and
high temperature in Moringa oleifera using the technique of conditioning seeds with
blue light and ethylene. The experiment was conducted in two stages the first being at
the Federal University of Campina Grande and the second at the State University of
Paraíba. Stage I was the application of seed conditioning, and stage II was the formation
of Moringa oleifera seedlings in a Fitotron-type growth chamber under water and heat
stress, in an experiment conducted in a completely randomized design, in a 2 x 2 x 3,
factorial scheme with two replacement levels of soil water lost by crop
evapotranspiration – ETc (50% and 100%), two thermal conditions, one with stress (40
°C day/35 °C night) and the other without stress ( 30 °C day/25 °C night) and three seed
conditionings consisting of a control - PRI 0 (unconditioned seeds), conditioning in
distilled water under irradiation with blue monochromatic light - PRI 1 and conditioning
in ethylene solution (500 mg L-1 of Ethrel) under irradiation with blue monochromatic
light – PRI 2, with five repetitions. Cell membrane integrity, water status, osmotic
adjustment indicators, antioxidative mechanism, gas exchange, photochemical
efficiency, seedling dry matter accumulation were evaluated. Biometric indicators,
chloroplast pigment contents, phytomass partition, growth and seedling quality indices,
leaf area indices, shoot biomass production and SPAD and growth rates. Data were
submitted to exploratory analysis of principal components, multivariate variance and
test of means. Thermal stress, ie, a temperature variation of 40 °C day/35 °C night,
caused an increase in the activity of catalase enzymes in the leaves and accumulation of
total soluble proteins in the roots. Abiotic, thermal and water stresses impaired gas
exchange, osmotic adjustment, photochemical efficiency and dry matter accumulation
of Moringa oleifera seedlings cultivated in a phytotron growth chamber. The seedlings
generated from seeds conditioned in ethylene solution under irradiation with blue
monochromatic light improve the physiological and biochemical characteristics for
greater tolerance to abiotic stresses. The occurrence of abiotic, thermal and water
stresses simultaneously caused a reduction in the quality of Moringa oleifera seedlings
in a phytotron growth chamber. However, conditioning seeds in solution with ethylene
phytohormone under irradiation with blue monochromatic light improved the quality of
seedlings subjected to these abiotic stresses. The combination of heat and water stress
increased the water content in the roots and the succulence of the leaves. The
conditioning of seeds in solution with the phytohormone ethylene under irradiation with
monochromatic blue light improves the accumulation of fresh matter, the water relations
and the growth indices of Moringa oleifera seedlings under abiotic, thermal and water
stress in a phytotron growth chamber.
