Salicylic acid can regulate phloem unloading in the root tip

Salicylic acid can regulate phloem unloading in the root tip In three-day-old maize (Zea mays L.) seedlings, we removed the endosperm, coleoptile with leaflets, and adventitious roots. Primary roots were exposed to 0–10−3 M salicylic acid (SA) for 1–5 h; scutellum, to 10−2 M 2-desoxy-D-glucose (2dG). 2dG-sucrose synthesized from 2dG was transported from scutella to the roots along the phloem. Its accumulation in 5-mm-long root tips was the measure of phloem unloading. At the concentrations higher than 10−4 M, SA suppressed unloading. Simultaneously, the uptake of 14C-5,5-dimethyloxazolidinedione (DMO) by root segments was inhibited, indicating cytoplasm acidification. 10−3 M SA also inhibited root respiration and growth. The lower SA concentrations (10−5 and 10−6 M) activated unloading under conditions of weak sucrose phloem transport to the root. They did not affect DMO uptake, respiration, and growth. 10−4 M SA stimulated unloading during 1- or 2-h exposure but did not affect it at longer treatments. A dependence of SA action on its concentration and exposure duration implies its involvement in the control of phloem unloading in the root tip. Russian Journal of Plant Physiology Springer Journals

Salicylic acid can regulate phloem unloading in the root tip

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SP MAIK Nauka/Interperiodica
Copyright © 2009 by Pleiades Publishing, Ltd.
Life Sciences; Plant Sciences ; Plant Physiology
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