Abstract:
Leaf shape diversity arises from differences in cellular level processes, like growth and proliferation. Leaves can broadly be classified as simple leaves, which form a single continuous blade, or compound leaves, where the blade is divided into distinct leaflets. How these cellular processes produce the observed diversity in morphology is a fascinating question in developmental biology. There have been long existing questions about the contribution of various leaf regions to this final form as well as the roles of different tissue layers. Here, we explored how growth and proliferation dynamics contribute to leaf and leaflet development across four species:
Arabidopsis, Cardamine, Tobacco and Tomato. We present a comparative study using 3D time-lapse datasets of these species, followed by a processing pipeline using PlantSeg and MorphoGraphX to obtain cellular segmentations, where individual cells can be tracked over time and 3D growth attributes can be quantified and extracted.
Across species, overall observed growth and proliferation increase as organs develop, but their spatial organisation differs. Regions where marginal outgrowths
such as serrations or leaflets form show locally elevated growth activity, whereas a
more evenly distributed expansion is seen in cases where no secondary structures
appear. Despite these local differences, our results suggest that the overall shape of
the organ emerges from broadly distributed growth patterns across the leaf, rather than from a small number of strongly localised growth centres. We observe differences in the timing of leaflet expansion relative to overall leaf size, as well as some differences in the dynamics of growth and proliferation between the species. To simulate the differences in leaflet development in the compound leaves of Cardamine and tomato, we developed a data-driven geometric model using measurements at different time points.
