Studies on the root and shoot water relations of an unusual Mexican maize and a typical corn belt hybrid
1997
Castro, V. | Daynard, T.B. | Thurtell, G.W.
In the semiarid region of northern Mexico, a significant amount of maize is grown in an unusual system referred to as "maiz de humedad", under which seeds are germinated in March with stored soil moisture, and plants usually survive more than 100 d without additional water until the rainy season begins in late June. In a series of experiments we sought to characterize the system and to compare the root-shoot growth and plant water relations of maize genotypes grown under this system and of a Corn Belt hybrid. The most important results from this study can be summarized as follows: 1. The maiz de humedad system is capable of producing three times more grain yield than the conventional system because the deep rooting system of humidity maize absorbs just enough water to maintain a small amount of transpiring leaf area during long dry periods prior to flowering. 2. Expanded leaves had higher turgor potentials than expanding leaves, due to a combination of lower leaf water potential and higher osmotic potential. 3. Root osmotic potential decreased in root tips growing under the water stress, the net result being that full root turgor potential was maintained even at root water potential differences between irrigated and water stressed plants of 1.0 MPa. 4. We expected the most important genotypic differences in this study to relate to the putative ability of maiz de humedad maize to grow and survive longer than a typical Com Belt hybrid under water stress. Although some statistical differences between genotypes were observed in leaf turgor potential (yp) at high levels of water stress, such differences in yp were never larger than 0.3 MPa. In addition, more osmotic content per cm2 of leaf was measured in maiz de humedad maize than in the hybrid. No conclusive adaptive advantages can be attributed to the small differences measured.
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