Short-term drought responses by seedlings of three maizes from contrasting environments in Michoacán, Mexico

Abstract

Alterations in precipitation regimes resulting from climate change threaten countries like Mexico, where rainfed ag- riculture for subsistence is widespread. However, numerous local maizes are cultivated throughout the country’s territory originated from a substantial environmental diversity. To investigate whether an environmental specializa- tion exists, responses to drought by maizes from three sites (elevations of 689, 2379, and 3638 m) in the state of Michoacán, Mexico, were studied in a greenhouse experiment. Plants were watered every other day for 21 days since sowing. Watering was withheld during 26 d and followed by a 10 d recovery period during which watering was resumed. Environmental conditions were contrasting among the sites of origin, e.g., annual precipitation defi- cit (from an ombrotherm diagram) was 33% at the lowest site and 9% and 0.3% for the sites at higher elevations. At the greenhouse, substrate water content for the control was ca. 34% (w/w) over the course of the experiment, it decreased to 1.9% at 26 d of water withholding and recovered after resuming irrigation. Tissue water content was ca. 92% for the control and decreased by 22-33% (depending on its origin) for the droughted individuals at the peak of the drought. Dry mass was lower for droughted individuals than for the control at the end of the experi- ment. Leaf chlorophyll content tended to decrease with plant age, but did not respond to water withholding. In contrast, proline tended to increase for droughted individuals. The the content of polyphenols, free-radical scav- enging compounds, tended to decrease during the recovery period, but not during drought. Neither did the anti- oxidant activity of leaf tissue respond to water withholding. Germplasm that is able cope with novel environmental conditions seems to exist in Mexico. Future studies should survey yield responses to different drought intensities for various maizes from dry environments to help identify traits useful in future breeding programs.