E. Zdunek et Sh. Lips, Transport and accumulation rates of abscisic acid and aldehyde oxidase activity in Pisum sativum L. in response to suboptimal growth conditions, J EXP BOT, 52(359), 2001, pp. 1269-1276
Pea plants (Pisum sativum L.) grown initially in nutrient solutions with ad
equate nitrogen supply (4 mM NO3-) were transferred to solutions containing
salt (50 or 100 mM NaCl), ammonium (4 mM) or a low nitrogen supply (0.4 mM
NO3-). No changes of abscisic acid (ABA) content were found in roots of st
ressed pea plants 9 d after the beginning of the treatments; however, accum
ulation of ABA in the leaves was observed. Old leaves accumulated ABA to a
higher extent than young leaves. Accumulation of ABA in leaves of ammonium-
fed plants and plants grown under low nitrogen supply occurred in the absen
ce of both increased ABA xylem loading rate and enhanced aldehyde oxidase (
AO, EC 1.2.3.1) activity in roots. Enhanced leaf AO activity was observed i
n all treatments, with the highest increase in old leaves. Among the three
AO isoforms (AO-1, AO-2 and AO-3) detected in extracts of pea leaves, the l
owest one AO-3 (highest mobility in the gel) correlated with ABA production
and showed the highest increment in response to the treatments. The increa
se of AO activity detected in leaves after 2 weeks of stress application wa
s less prominent than after 9 d, suggesting a transient enhancement of ABA
production following the onset of stress. An increase of ABA xylem loading
rate as well as AO root activity 4 d and 9 d after application of the treat
ments was observed only in salt-treated plants followed by a decrease after
14 d in 100 mM NaCl. Decreased cytokinin (trans-zeatin riboside) delivery
rate into the xylem sap was observed in all treatments. The role of abscisi
c acid and cytokinins as positive and negative growth signals, as well as t
he involvement of root-generated ABA on ABA accumulation in leaves is discu
ssed.