EMERGENCE, ELONGATION, AND SENESCENCE OF MAIZE SILKS

In maize (Zea mays L.), duration of silk receptivity to pollen is limi ted after silks emerge from the husks. Whether this loss in receptivit y reflects senescence of the entire ear or individual pistillate flowe rs is not known. Therefore, we examined the relationships between emer gence, elongation, and senescence of silks in two hybrids varying in e ar development. Plants were grown in soil in the greenhouse. For both hybrids, the first silks to emerge were from Flower Positions 6 to 15 from the base of the ear. These were followed by silks from progressiv ely younger flowers in acropetal sequence. Silks of all flowers were e xposed within 4 (Hybrid 1) to 8 (Hybrid 2) days. Silk elongation was m ost rapid during the first day of exposure, declined progressively wit h time, and ceased completely within 9 to 11 d. Silks began to senesce almost-equal-to 7 to 8 d after emergence from the husk. The first sil ks to be exposed were also the first to senesce. Senescence was first evident as a loss of turgidity in tissues at the basal 3 mm of the sil k, followed by the complete collapse of this tissue. In Hybrid 1, this process progressed from the peripheral cells towards the central tiss ues. In Hybrid 2, the central tissues of the silk were the first to co llapse. There was no apparent effect of flower position on the interva l between silk emergence and silk senescence, or on the senescence pro cess. These results show that silks of maize undergo a well-defined pa ttern of emergence, elongation, and senescence. The pattern is similar across flower positions on the ear; however, the timing and duration of these developmental events are characteristic of individual hybrids .