Discussion
Existing literature has revealed that shading increases leaf senescence,
affects plant growth, and decreases crop yield
(Gindaba & Midgley, 2005;
Spundova et al., 2005). However,
different shading patterns, exposure time, the intensity of shade, and
tissue position will lead to varied responses by a plant. Until now, the
mechanism involved in how partial shading delays leaf senescence in
maize remains unclear. In our previous study, the phenotype of delaying
maize leaf senescence under narrow-wide row planting patterns in the
field was investigated partially (Feng et
al., 2020). The cultivation patterns in the field are shown in
Supporting Information Figure S4 for a better understanding. Therefore,
the present study aimed at providing a detailed mechanism underlying how
partial shading delays leaf senescence in maize. Our work is the first
report about the synergy in response to shade between two side leaves in
maize and how partial shading decreases leaf senescence in maize through
increased photosynthetic performance and increased carbon fixation,
which finally balances maize yield (Table 2, 3). Our phenotypic data,
photosynthetic efficiency, phytohormones synthesis, antioxidants enzyme
activity, plant sugar accumulation, carbon activity, and gene expression
analysis provided evidence that the partial shading in maize enhances
photosynthetic carbon fixation, which delays the leaf senescence
resulting in an extended grain-filling period. The phenotypic response
of maize plants to different light intensity treatments suggested that
full shade induced leaves senescence rapidly compared to partial shading
(Supporting Information Figure S1, Table S1), which is consistent with a
previous report (Spundova et al., 2005).
Partial shade delayed senescence more significantly than the normal
light, so we used the normal light treatment as a control to explain the
mechanism of partial shade induced delayed senescence in maize.