The growth of vegetative and reproductive structures (leaves and silks) respond similarly to hydraulic cues in maize.

The elongation of styles and stigma (silks) of maize (Zea mays) flowers is rapid (1-3 mm h(-1) ), occurs over a short period and plays a pivotal role in reproductive success in adverse environments. Silk elongation rate was measured using displacement transducers in 350 plants of eight genotypes during eight experiments with varying evaporative demand and soil water status. Measured time courses revealed that silk elongation rate closely followed changes in soil water status and evaporative demand, with day-night alternations similar to those in leaves. Day-night alternations were steeper with high than with low plant transpiration rate, manipulated via evaporative demand or by covering part of the leaf area. Half times of changes in silk elongation rate upon changes in evaporative demand or soil water status were 10-30 min, similar to those in leaves. The sensitivity of silk elongation rate to xylem water potential was genetically linked to that of leaf elongation rate. Lines greatly differed for these sensitivities. These results are consistent with a common hydraulic control of expansive growth in vegetative and reproductive structures upon changes in environmental conditions via a close connection with the xylem water potential. They have important implications for breeding, modelling and phenotyping.

Drought-induced changes in anthesis-silking interval are related to silk expansion: a spatio-temporal growth analysis in maize plants subjected to soil water deficit.

The growth and emergence of maize silks has a considerable importance in yield determination under drought conditions. Spatial and temporal patterns of the rates of tissue expansion and of cell division were characterized in silks of plants subjected to different soil water potentials. In all cases, silk development consisted of four phases: (1) cell division and tissue expansion occurred together uniformly all along the silk; (2) cell division progressively ceased from tip to base, while expansion remained spatially uniform including during the phase (3) after the cessation of cell division; and (4) as the silk emerged from the husks, expansion ceased in the emerged portion, probably because of direct evaporative demand, while the relative growth rate progressively decreased in the enclosed part. The rates of tissue expansion and cell division were reduced with water deficit, resulting in delayed silk emergence. The duration of cell division was not affected, and in all cases, the end of cell division in the silk coincided with anther dehiscence. The duration of phase 3, between the end of cell division and the arrest of cell growth in silk apex, considerably increased with water deficit. It corresponded to the anthesis-silking interval used by breeders to characterize the response of cultivars to stress.