Tow field experiments were carried out at the Experimental Farm
Station of the Faculty of Agriculture Moshtohor, Benha University, Kalubia
Governorate, Egypt, during two successive summer seasons of 2012 and
2013 on snap bean cv. Bronco (Phaseolus vulgaris L.) under drip irrigation
system. The aim of this study was to investigate the effect of applied
antioxidants (ascorbic acid at 200, 400 mg/L and putrescine at 10, 20 mg/L),
potassium at 250, 500 mg/L and arbuscular mycorrhiza (AM) at two water
stress levels i.e., 35, 50 and 100% of ETo as control (i.e., irrigation with
1326.5, 1895.25 and 3790.5 m3/fed, respectively of water requirement of
snap bean plants) on vegetative growth characters, yield and its components,
biochemical compositions, anatomical characteristics of snap bean plants.
The obtained results showed that, foliar application of ascorbic acid
(400 mg/L), putrescine (20 mg/L), potassium citrate (500 mg/L) and
mycorrhiza significantly increased all of the studied growth characteristics
i.e., plant height, number of leaves and leaf area/plant, fresh and dry weight
of stem and leaves/plant. Also, these applied treatments used significantly
increased yield and its components i.e., number and weights of green
pods/plant and total green pods yield/fed, pod length and diameter, number
of dry pods/plant, seeds number, seeds weight/plant and fed and 100 seeds
weight. Meanwhile, water stress levels treatments (50 and 35% of ETo)
showed significant decrease all the tested above mentioned growth and yield
characteristics in the two seasons.
Leaf relative water content (%), photosynthetic pigments in leaves and
pods, N, P, and K and protein content, endogenous phytohormone promoters
of auxins, gibberellins and cytokinins, promoters/inhibitors ratio were
increased with all studied applications of these antioxidants, K and addition
of mycorrhiza whereas, they decreased with the two water stress levels used
(50 and 35% of ETo) as compared with unstressed plants. Results also
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showed that water stress levels (50 and 35% of ETo) induced marked
increase concentration of organic compounds (i.e., proline, total soluble
sugar, total free amino acids and total phenols) and antioxidant enzymes
activity (POX, SOD, CAT and PPO) and ABA concentration in leaves
during flowering and fruiting stages of snap bean plants.
The data also indicated that, foliar application with ascorbic acid (400
mg/L) and putrescine (20 mg/L) followed by potassium citrate (500 mg/L)
and addition of mycorrhiza had a positive effect on all studied anatomical
characteristics of stem section ( i.e., epidermis, cortex layers, dimensions of
vascular bundles, thickness of phloem tissue and cambial region, xylem
tissue, xylem vessel) and leaf blade section (i.e., thickness of midrib, length
& width of vascular bundle, phloem & xylem tissues and number and
diameter of xylem vessels in vascular bundle and leaf blade thickness).
While the used treatments of water stress levels (50 and 35% of ETo) had a
negative effect on most of the studied anatomical characteristics of stem and
leaf of snap bean plants compared with unstressed plants treatments (100%
of ETo). These decreases were more pronounced at high water stress level
(35% of ETo).
It could be concluded that foliar application with ascorbic acid at 400
mg/L, putrescine at 20 mg/L and potassium citrate at 500 mg/L reduced the
harmful effects of water stress and improves growth and production of snap
bean plants under normal and water stressed conditions (50% of ETo). |
