الفهرس 
Effect of gibberellic acid (GA 3 ) on growth traits, physio-biochemical parameters, and yield components of plants grown under drought stress:Only 14 pages are availabe for public view
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Abstract
The use of growth regulators such as gibberellic acid (GA 3 ) and biostimulants,
including diluted bee-honey (Db-H) can improve drought tolerance in many crops, including
faba bean (Vicia faba L.). Db-H contains high values of osmoprotectants, mineral nutrients,
vitamins, and many antioxidants making it an effective growth regulator against
environmental stress effects. Therefore, the present study was planned to investigate the
potential improvement in faba bean plant performance (growth and productivity) under full
watering [100% of crop evapotranspiration (ETc)] and drought stress (60% of ETc) by foliar
application of GA 3 (20 mg L -1 ) or Db-H (20 g L -1 ). The ameliorative impacts of these growth
regulators on growth, productivity, physio-biochemical attributes, nutrient status, antioxidant
defense system, and phytohormones were evaluated. GA 3 or Db-H attenuated the negative
influences of drought stress on cell membrane stability, ion leakage, relative water content,
nutrient status, leaf pigments related to photosynthesis (chlorophylls and carotenoids), and
efficiency of the photosystem II (PSII in terms of F v /F m and performance index), thus
improving faba bean growth, green pod yield, and water use efficiency. Drought stress caused
an abnormal state nutrients and photosynthetic machinery due to increased indicators of
oxidative stress [malondialdehyde (MDA), hydrogen peroxide (H 2 O 2 ) and superoxide (O 2 •− )],
associated with increased osmoprotectants (proline, glycine betaine, soluble sugars, and
soluble protein), non-enzymatic antioxidants (ascorbic acid, glutathione, and α-tocopherol),
and enzymatic antioxidant activities (superoxide dismutase, catalase, glutathione reductase,
and ascorbate peroxidase). However, foliar-applied GA 3 or Db-H mediated further increases
in osmoprotectants, antioxidant capacity, GA 3 , indole-3-acetic acid, and cytokinins, along
with decreased levels of MDA and abscisic acid. These results suggest the use of GA 3 or Db-
H at the tested concentrations to mitigate drought-induced damage in faba bean plants to
obtain satisfactory growth and productivity under a water deficit of up to 40%.
Keywords: Faba bean; Drought; Growth and productivity; Antioxidants defense system;
Biostimulants.