Abstract
ABSTRACT Although it is relatively well known that adult plants tend to accumulate proline and trehalose in their tissues as a physiological mechanism in response to drought, there is scarce information about the development of this physiological response in seeds. Thus, the objective of this research was to verify if maize seeds are able to develop mechanism of osmoprotection, when are germinating under low osmotic potential, and the possibility to use the levels of trehalose and proline in a defined seed part, aiming to differentiate genotypes regarding drought tolerance. The experiment was performed as a factorial arrangement of 2 x 5 (2 hybrids x 5 osmotic potential) within a completely randomized design, with four replicates. It was found that the proline content in the embryo axis of maize seeds germinating under water limitation is directly proportional to the intensity of this stress. Distinct hybrids show different proline levels accumulated in the embryo axis, when seeds are germinating under the same conditions of water limitation. The trehalose content tends to decrease in the embryo axis and in the endosperm of maize seeds germinating under increasing water limitation, but the reduction is not directly proportional to osmotic potential.
Highlights
The understanding on drought tolerance in crop plants is a matter of great relevance, once water limitation is one of the greatest constraints for agriculture (Rodriguez-Salazar et al, 2009; Xoconostle-Cázarez et al, 2010)
The restriction on water availability induced a reduction of about 47% for DKB-390 hybrid (DKB) and 52% for DAS-2B710 (DAS) in the germination index (GI) of seeds, considering data obtained at the lowest osmotic potential (-1.2 MPa, Figure 1A)
The proline contents in the embryo axis of maize seeds germinating under water limitation are directly proportional to the intensity of this stress
Summary
The understanding on drought tolerance in crop plants is a matter of great relevance, once water limitation is one of the greatest constraints for agriculture (Rodriguez-Salazar et al, 2009; Xoconostle-Cázarez et al, 2010). Based on studies with adult or young plants, it was stated that generally the response to water limitation is the development of an osmoprotection mechanism This mechanism is initiated by an osmotic adjustment to keep plant metabolism running, at least at a minimum rate, and for a relatively short period of time under drought (Mohammadkhani & Heidari, 2008). This phenomenon comprises the synthesis of certain compatible solutes that may have a prime role on the protection of key proteins, on stabilizing cell membranes, and on the control of instable chemicals species (Mohammadkhani & Heidari, 2008, Xoconostle-Cázarez et al, 2010). It is advocated that trehalose and proline are used as energy sources, and that proline may be metabolized as nitrogen source readily available for plant re-establishment just after the period of water limitation (Kavi Kishor et al, 2005; Trovato et al, 2008)
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