Water Deficit Affects Receptivity of Maize Silks

Drought during anthesis decreases seed set in maize ( Zea mays L.) even if pollination occurs. To test whether low silk water potential (ψ w ) decreases silk receptivity, we examined silk development, pollen‐silk interaction, and kernel set in two hybrids grown in a greenhouse and exposed to a brief water deficit after silks emerged from the husks. Low silk ψ w directly affected silk development. Silk elongation was inhibited as silk ψ w decreased, and no growth occurred at silk ψ w below −0.8 MPa. Silk senescence (collapse of basal silk tissue) was delayed, compared with controls, when silk elongation was arrested by low ψ w within 3 days after the first silks appeared (DAFS). similar water deficit 5 DAFS, however, hastened silk senescence. The change in silk development had a direct effect on kernel set. Low silk ψ w decreased set 20 to 40% 3 DAFS, and decreased set almost completely 5 DAFS. Pollen tubes were observed in >90% of silks pollinated at ψ w between −1.0 and −1.3 MPa, although there were fewer tubes per silk. Tube growth was slow at low silk ψ w , but tubes failed to reach the ovary only after silks had senesced. These results indicate that low ψ w imposed <4 DAFS limited kernel set primarily by causing developmental failure within the ovary, not loss of silk function. Low ψ w imposed >5 DAFS limited kernel set by hastening silk senescence. Thus, water deficits at anthesis can cause loss of silk receptivity in maize, but only when low silk ψ w occurs >5 d after silks emerge from the husks.