Figure 8.

Drought or Osmotic Stress Improves the Survival of lew1 Plants in the Dark or under Weak Light

(A) Ten-day-old seedlings in soil were subjected to water withholding for 7 d to give a modest drought treatment (Drought) in the light and then incubated in the dark for 15 or 20 d, or in the light for 15 d, without watering. Wild-type but not lew1 plants died from drought treatment for 15 d in the light. All lew1 plants died from drought at 20 d in the light. Plants without drought treatment (Watered) were kept in the light for 15 d or in the dark for 15 or 20 d.

(B) After 20 d, the drought-treated plants in the dark were watered and moved, together with plants without drought treatment in the dark, to light for an additional 3 d. No lew1 plants without drought treatment in the dark survived, but all lew1 plants with drought treatment in the dark survived. No wild-type plants died under the conditions used.

(C) Osmotic stress imposed by mannitol, NaCl, or glycerol increased the survival of lew1 seedlings in MS medium without sucrose under weak light. Four-day-old seedlings grown on MS medium with 3% sucrose were moved to MS medium without sucrose (−), with sucrose (3%), or without sucrose but with 100 mM mannitol, 180 mM NaCl, or 1.5% glycerol and cultured for 7 d. All lew1 seedlings on MS medium without sucrose died, while all wild-type seedlings survived. In other treatment conditions, all lew1 and wild-type seedlings survived.

(D) lew1 seedlings are more tolerant to high-salt stress than wild-type seedlings. Four-day-old seedlings were moved to MS medium containing 3% sucrose with different concentrations of NaCl (0, 75, 120, or 180 mM) and cultured for 10 d. There was no clear growth difference at 0, 75, and 120 mM NaCl between the wild type and lew1. However, at 180 mM NaCl, lew1 seedlings grew better than wild-type seedlings.