| Pak. J. Bot., 37(4): 865-874, 2005. | Back to Contents | ||||
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Updated: 09-07-09 | ||||
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SEED TREATMENT WITH PHYTOHORMONES AND CROP PRODUCTIVITY. III. PHYSIOLOGICAL/BIOCHEMICAL CHANGES IN GERMINATING SEEDS AND ROOTING HARACTERISTICS OF WHEAT (TRITICUM AESTIVUM L.) FOLLOWING EXPOSURE TO 2,4-D F. AZAM, A. LODHI, S. FAROOQ, R. HARRY-O'KURU* AND S.H. IMAM**
Abstract: The 2,4-dichlorophenoxy acetic acid (2,4-D) is a commonly used herbicide.
Over the past few years, its auxin-like action has been extensively
exploited for modifying plant roots to achieve enhanced bacterial colonization
and N2 fixation. We adopted seed soaking as a mode of administering
2,4-D and observed changes in seed germination and rooting characteristics
of wheat (Triticum aestivum L.). Soaking of seeds in an aqueous
solution containing 2,4-D (0 - 200 g mL-1) resulted in delayed
or arrested seed germination. However, the number of primary roots increased
dramatically and this effect was more pronounced at higher concentrations
of 2,4-D. Delay in seed germination was due to decreased metabolism
of seed reserves as observed by much lowered respiration rates (loss
of CO2). FTIR spectroscopy revealed a relatively slow starch
degradation in 2,4-D treated seeds as observed by the intensities of
the characteristic absorption peaks of a broad OH band and the fingerprint
region of starch. Number of primary roots increased significantly due
to soaking of seed in 2,4-D solution but showed stunted growth. Scanning
electron microscopy (SEM) of roots exposed to 2,4-D in the growth medium
showed a strengthening of stellar system but damaged cells at the surface.
Leakage of cellular material from damaged cells caused an increased
colonization of roots by bacteria (revealed by SEM) and their subsequent
proliferation in the rooting medium. Nuclear Institute for Agriculture and Biology (NIAB), Faisalabad, Pakistan.
New Crop Research, NCAUR, ARS-USDA, Peoria, IL, 61604 USA. |
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