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Keywords:

  • Chilling;
  • drought;
  • tolerance;
  • Zea mays (maize);
  • growth analysis

summary

We investigated the effectiveness of pre-drought treatment to acclimate a chilling-sensitive variety of maize (Errazu) against chilling injury. We tested two methods of applying drought: (a) withholding water during 17 d in perlite culture, and (b) suppressing water by keeping plants out of the nutrient solution at time intervals (2, 4, 6, 8 and 10 h) on five successive days in hydroponic culture. Drought treatments were applied to maize seedlings either in perlite or hydroponic culture before chilling (5 d at 5°C and 150 μmol m−2 s−1 photosynthetic photon fluence rate and then 5 d of recovery at 25°C). Both experiments were carried out under low irradiance to avoid photo-oxidation damage during chilling. Plant growth (relative growth rate, RGB; net assimilation rate, NAR; leaf area ratio, LAR; specific leaf area, SLA; and leaf weight ratio, LWR), percentage of necrotic leaf area, leaf relative water content (RWC), leaf water (Ψleaf) and osmotic (Ψs) potentials, specific plant transpiration, total water absorption and CO2 exchange rate (CER) were examined in drought-treated and non-treated maize seedlings during chilling and after a 5 d recovery period, RGR and NAR of droughted maize seedlings were higher than those of non-droughted seedlings during recovery, irrespective of the growth medium (perlite or hydroponic). Chilling-induced leaf necrosis was significantly lower in droughted than in non-droughted seedlings. Droughted plants had higher water status (higher leaf RWC, Ψleaf and Ψs) after 5 d of chilling, mainly owing to stomatal closure induced by drought. The CER declined to a similar extent in droughted and non-droughted maize seedlings on chilling, but during recovery droughted seedlings showed significantly higher CO2 fixation rate than non-droughted seedlings. Leaf conductance of water vapour (g) and CO2 intercellular concentration (C2) analysis led to the conclusion that chilling-induced CER inhibition was not due to a stomatal limitation. Droughted seedlings of maize had a better water use efficiency of photosynthesis (WUEph) than non-droughted plants. We conclude that pre-drought treatment hardened the chilling sensitive variety of maize Errazu against chilling injury.