KOCHIA (KOCHIA-SCOPARIA) POLLEN DISPERSION, VIABILITY AND GERMINATION

Kochia pollen dispersion was measured during 24 and 48 h periods from a kochia population in an 8- by 10-m area in the center of a 1.6 ha fa llow field. Pollen counts from traps at 50- and 100-cm heights decline d rapidly with increasing distance from the pollen source. Pollen depo sition was highest along the prevailing wind direction: up to 23 polle n grains cm-2 were recovered 50 m from the pollen source along the sou theast (SE) vector. Nonlinear regression analysis of pollen deposition along the SE vector was used to estimate that 99.9% of shed pollen wo uld be deposited within 154.4 m of the source. Viability of pollen fro m greenhouse-and field-grown plants was measured using staining and ge rmination assays. Of four pollen stains tested, only 1,2,3-triphenyl t etrazolium chloride gave consistent results and did not stain heat-kil led pollen. Depending on environmental conditions, kochia pollen remai ned viable from less than 1 d to 12 d. Length of kochia pollen viabili ty was shortest under high temperatures (22 and 28 C) and low relative humidity (7 and 32%). Less than 0.5% germination was observed in 1.1% agar media with various additions; however, up to 17.8% germination w as observed after incubation at 28 C in 100% relative humidity. Nomenc lature: Kochia, Kochia scoparia (L.) Schrad #3 KCHSC.