New Plant Growth Regulators Protect Photosynthesis and Enhance Growth Under Drought of Jack Pine Seedlings |
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Authors: | L R Rajasekaran T J Blake |
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Institution: | (1) Department of Plant Science, Nova Scotia Agricultural College, PO Box 550, Truro, Nova Scotia, Canada B2N 5E3, CA;(2) Faculty of Forestry, Earth Sciences Centre, University of Toronto, 33 Wilcocks Street, Toronto, Canada M5S 3B3., CA |
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Abstract: | To determine whether natural plant growth regulators (PGRs) can enhance drought tolerance and the competitive ability of
transplanted seedlings, 1.5-year-old jack pine (Pinus banksana Lamb.) seedlings were treated with homobrassinolide, salicylic acid, and two polyamines, spermine and spermidine, triacontanol,
abscisic acid (ABA), and the synthetic antioxidant, Ambiol. PGRs were fed into the xylem for 7 days and plants were droughted
by withholding water for 12 days. ABA, Ambiol, spermidine, and spermine at a concentration of 10 μg L−1 stimulated elongation growth under drought, whereas ABA, Ambiol, and spermidine maintained higher photosynthetic rates, higher
water use efficiency, and lower Ci/Ca ratio under drought compared with control plants. The damaging effects of drought on
membrane leakage was reversed by Ambiol, ABA, triacontanol, spermidine, and spermine. Because ABA, Ambiol, and both polyamines
enhanced elongation growth and also reduced membrane damage in jack pine under drought, they show promise as treatments to
harden seedlings against environmental stress. The protective action of these compounds on membrane integrity was associated
with an inhibition of ethylene evolution, with a reduction in transpiration rate and an enhancement of photosynthesis, which
together increased water use efficiency under drought. Although most of the tested compounds acted as antitranspirants, the
inhibition in membrane leakage in ABA-, Ambiol-, and polyamine-treated plants appeared more closely related to the antiethylene
action.
Received December 30, 1998; accepted October 14, 1999 |
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Keywords: | , ABA—,Ambiol—,Drought—,Ethylene—,Homobrassinolide—,Membrane leakage—,Photosynthesis—,Pinus banksiana—,Polyamines—,Salicylic,,,,,acid—,Triacontanol |
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