Cellular dynamics in the maize leaf growth zone during recovery from chilling depends on the leaf developmental stage

Zea mays, a major crop, is highly sensitive to chilling which frequently occurs during its seedling stage and negatively affects yields. Although the direct effect of chilling is well-studied, the mechanisms determining the subsequent recovery are still unknown. Our goal is to determine the cellular basis of the dynamic leaf growth response to chilling and during recovery of leaves exposed before or after their emergence. We first studied the effect of a 3-day cold spell on leaf growth at the plant level. Then, we performed a kinematic analysis to analyse the dynamics of cell division and elongation during recovery of the 4th leaf after exposure to cold before or after emergence. Our results demonstrate that cold more strongly reduced the final length of non-emerged than emerged leaves (-13 vs -18%). This was not related to growth differences during cold, but a faster and more complete recovery of the growth of emerged leaves. Kinematic analysis showed that this difference was due to a higher cell division rate on the 1st and a higher cell elongation rate on the 2nd-day of recovery, respectively. The dynamics of cell division and expansion during recovery determine developmental stage-specific differences in cold tolerance of maize leaves.