EMERGENCE, ELONGATION, AND SENESCENCE OF MAIZE SILKS

In maize (Zea mays L.), duration of silk receptivity to pollen is limited after silks emerge from the husks. Whether this loss in receptivity reflects senescence of the entire ear or individual pistillate flowers is not known. Therefore, we examined the relationships between emergence, elongation, and senescence of silks in two hybrids varying in ear 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 progressively younger flowers in acropetal sequence. Silks of all flowers were exposed within 4 (Hybrid 1) to 8 (Hybrid 2) days. Silk elongation was most rapid during the first day of exposure, declined progressively with 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 silks 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 silk, followed by the complete collapse of this tissue. In Hybrid 1, this process progressed from the peripheral cells towards the central tissues. In Hybrid 2, the central tissues of the silk were the first to collapse. There was no apparent effect of flower position on the interval between silk emergence and silk senescence, or on the senescence process. These results show that silks of maize undergo a well-defined pattern 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.