Salt-stress-induced ABA accumulation is more sensitively triggered in roots than in shoots.
Salt-stress-induced ABA accumulation in maize root tissues was compared with that in leaf tissues. While salt stress with NaCl resulted in a significant ABA accumulation in root tissues (up to 10-fold), the same stress only led to a small ABA accumulation in leaf tissues (about 1-fold). Pretreatment with ethylene glycol (EG), a permeable and inert monomer of PEG, could prevent the shrinkage of cell volume and completely block the ABA accumulation in leaf tissues under salt stress, but substantial salt-induced ABA accumulation was still observed in root tissues following such pretreatment. Hypotonic salt solutions, i.e. below 100 mM NaCl, still induced a significant ABA accumulation (more than 3-fold) in roots, but showed no effect on that in leaf tissues. Results suggest that the salt-stress-induced ABA accumulation in roots may also be triggered by an osmosensing mechanism, which is in addition to the perception of the changes in reduced cellular volume or plasmalemma tension that leads to ABA accumulation in leaves. When leaf and root tissues were immersed into salt solutions, salt entered into the cells as a function of time and salt concentrations. Such entrance apparently led to a loss of sensitivity of leaf tissues to accumulate ABA under the salt stress, and also prevented the leaf tissues from responding to further air-drying in terms of ABA accumulation. Roots showed no such responses. Results suggest that the entrance of salt into leaf cells brought about some toxic effect that might have reduced the capability of leaf cells to produce ABA under dehydration.
Jia
Wensuo
W
College of Horticulture, China Agricultural University, Beijing, China.
Wang
Youqun
Y
Zhang
Shuqiu
S
Zhang
Jianhua
J
D000040:Abscisic Acid / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000222:Adaptation, Physiological / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D019855:Ethylene Glycol / Q000494:pharmacology; D018517:Plant Roots / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D018520:Plant Shoots / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D012965:Sodium Chloride / Q000494:pharmacology*; D013997:Time Factors; D003313:Zea mays / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*
D012965:Sodium Chloride; D000040:Abscisic Acid; D019855:Ethylene Glycol