Water Relations of Growing Maize Coleoptiles

Abstract

Water relations of growing segments of maize (Zea mays L.) coleoptiles were investigated with osmotic methods using either mannitol (MAN) or polyethylene glycol 6000 (PEG) as external osmotica. Segments were incubated in MAN or PEG solutions at 0 to -15 bar water potential (#o) and the effects were compared on elongation growth, osmotic shrinkage, cell sap osmolality (OC), and osmotic pressure (.w,). The nonpenetrating osmoticum PEG affects ir, in agreement with Boyle-Mariotte's law, i.e. the segments behave in principle as ideal osmometers. There is no osmotic adjustment in the 4,o range permitting growth (0 to -5 bar) nor in the P,o range inducing osmotic shrinkage (-5 to -10 bar). Promoting growth by auxin (IAA) has no effect on the osmotic behavior of the tissue toward PEG. In contrast to PEG, MAN produces an apparent increase in -r1 accompanied by anomalous effects on segment elongation and shrinkage leading to a lower value for 0, which establishes a growth rate of zero and to an apparent recovery from osmotic shrinkage after 2 hours of incubation. These effects can be quantitatively attributed to uptake of MAN into the tissue. MAN is taken up into the apoplastic space and the symplast as revealed by a large temperature-dependent component of MAN uptake. It is concluded that MAN, in contrast to PEG, is unsuitable as an extemal osmoticum for the quantita-

Physio-Biochemical Responses of Oil Palm (Elaeis guineensisJacq.) Seedlings to Mannitol- and Polyethylene Glycol-Induced Iso-Osmotic Stresses

“…SH, RL, LA, FW and DW of oil palm seedlings were retarded by water shortage, especially in plants under PEG-induced osmotic stress. Similar results in the overall growth performance have been recorded in maize coleoptiles (Hohl and Schopfer, 1991). Osmotic stress induced by PEG, especially high-molecular weight PEG (MW>1000) has been reported to limit water uptake and O 2 -disolution (Lawlor, 1970;Janes, 1974), whereas mannitol has been used only as an osmoticum with low absorption rate by the root tissues of plants (<5% radioactive labeling) (Smith and Smith, 1973;Flora and Madore, 1993;Vítová et al, 2002).…”

Effect of Hormonal Priming (GA3) and Osmopriming on Behavior of Seed Germination in Wheat (Triticum aestivum L.)

“…Osmotic solutions are used to impose water stress reproducibly under in vitro conditions (Pandey & Agarwal, 1998). Polyethylene glycol molecules with PEG 6000 are inert, non ionic and virtually impermeable chains that have frequently been used to induce water stress and maintain uniform water potential throughout the experimental period (Hohl & Schopfer, 1991;Lu & Neumann, 1998). Molecules of PEG 6000 are small enough to influence the osmotic potential, but large enough to not be absorbed by plants (Carpita et al, 1979;Saint-Clair, 1976).…”

Physiological and comparative proteomic analyses of Thai jasmine rice and two check cultivars in response to drought stress

“…PEG6000 affects on changes of stress-related enzymes and compounds in 5-day-old rice seedlings more than mannitol (Pandey et al 2004). In contrast to PEG6000, mannitol can be transported into root cells lowering its ability to produce water stress in plants (Hohl & Schopfer 1991). Thus, in order to avoid the adaptation of rice seedlings under conditions of mild stress, PEG6000 is preferred for use as an osmoticum.…”

“…The effect of PEG6000 on these parameters was greater than upon treatment with mannitol, and these effects became more severe as the stress increased (Figure 1). There are some comparative studies on the effect of PEG and mannitol as osmotic agents on plants (Hohl & Schopfer 1991;Pandey et al 2004;Slama et al 2007). PEG6000 affects on changes of stress-related enzymes and compounds in 5-day-old rice seedlings more than mannitol (Pandey et al 2004).…”