Abstract:
We studied the drought response of eight commercial hybrid maize lines with contrasting drought sensitivity together with
the reference inbred line B73 using a non-invasive platform for root and shoot phenotyping and a kinematics approach to
quantify cell level responses in the leaf. Drought treatments strongly reduced leaf growth parameters including projected
leaf area, elongation rate, final length and width of the fourth and fifth leaf. Physiological measurements including water use
efficiency, chlorophyll fluorescence and photosynthesis were also significantly affected. By performing a kinematic analysis,
we show that leaf growth reduction in response to drought is mainly due to a decrease in cell division rate, whereas a
marked reduction in cell expansion rate is compensated by increased duration of cell expansion. Detailed analysis of root
growth in rhizotrons under drought conditions revealed a strong reduction in total root length as well as rooting depth and
width. This was reflected by corresponding decreases in fresh and dry weight of the root system. We show that phenotypic
differences between lines differing in geographic origin (African vs. European) and in drought tolerance under field
conditions can already be identified at the seedling stage by measurements of total root length and shoot dry weight of the
plants. Moreover, we propose a list of candidate traits that could potentially serve as traits for future screening strategies.
