An integrated approach to unravel the growth response of maize leaves to drought
29 June 2016
UAntwerpen, Campus Groenenborger, V0.08 - Groenenborgerlaan 171 - 2020 Antwerpen
Gerrit Beemster & Han Asard
PhD defence Viktoriya Avramova - Faculty of Science, Department of Biology
Drought is presumably the single most yield-limiting factor for crops and its occurrence is forecasted to increase under future climate scenarios. The work, described in this thesis, gives an integrated overview of the plant growth responses to water deficiency, which we studied using the maize leaf as a model system. We conducted a high-resolution examination of the molecular regulation of cell division and cell expansion under optimal and drought conditions and demonstrated the complexity of the drought response at different organizational levels. Our main findings were that an increased photosynthetic capacity of the leaves, developed under drought conditions, leads to enhanced photosynthesis upon re-watering, facilitating the often-observed growth compensation of the plants. Additionally, we found that increasing the antioxidant capacity in the proliferation zone increases leaf growth rate by stimulating cell division.
The leaves of drought-tolerant hybrids were better protected during the stress, which was mainly related to higher activity of the main redox-regulating enzymes in the meristem of the leaves, where the largest effects of the growth process are occurring, resulting in less H2O2 production in this zone and thus improved growth. Moreover, we provide lists of molecular, cellular and physiological traits, which correlate with drought tolerance and could serve as screening parameters at the early seedling stage, which would facilitate the process of selection, avoiding the laborious and time-consuming field trials. We also provided lists of candidate genes, whose transcriptional regulation in response to drought affected directly the protein level and could serve as targets for further research of drought sensitivity.
Thus, the work presented in this thesis represents a significant progress of our understanding of how plants adjust their growth under drought conditions and the mechanisms that regulate the drought response at the different organizational levels. This knowledge can contribute to increased drought tolerance in crops and therefore higher productivity under suboptimal (future) climate conditions.