Understanding the timing sequence of maize leaf development

Simulating the development of leaves is an essential component of crop and plant models. Most crop models simulate the development of leaf area index by a global equation, whilst most functional-structural models detail the successive timing of development and senescence of individual leaves along plant shoots. This added complexity allows for a more precise expression of a large range of plant–environment interactions and how the plants respond to stress.

As with any model, detailed biological information is a prerequisite for accurate model predictions. With respect to leaf development, describing the full sequence of leaf extension from its initiation to its full unfolding is a pre-requisite to precisely predicting plant stress responses. For the crop species maize (Zea mays), much of this information is still lacking adequate detail for incorporation into models.

Photographs of two maize cultivars derived by selfing and selection for the time of female flowering from the maize inbred line MBS847. Phenotypes are similar except the later female flowering in M40 is associated with a higher leaf extension rate and a bigger plant size. Image credit: Vidal *et al.*

In their new study published in AoBP, Vidal et al. analyse the sequence of leaf development and leaf extension rates of two maize cultivars with the same genetic background but contrast in their leaf size. They characterized the dynamics of the blade and sheath lengths by dissecting plants every 2–3 days. They then analysed how differences in leaf size were built up and examined coordination between the emergence of organs and phases of their extension.

Leaf developmental timing markedly differed before and after tassel initiation, resulting in successive leaves increasing in length up the plant to the ear position and then decreasing in length above this. Both cultivars were quite similar with regards to the timing of events yet were distinguished by faster leaf extension rates in the taller cultivar. This work helps to clarify the features involved in the timing of leaf developmental events and the pattern of successive leaf sizes along a maize shoot. This information will be valuable to improving maize models.