Environmental control and evidence for predetermination of pollen embryogenesis inNicotiana tabacum pollen

Summary The effect of daylenght and temperature for the donor plants (Nicotiana tabacum var. Badischer Burley) on the formation of pollen competent for embryogenesis (P-pollen) by the three possible routes (during normal flower developmentin situ (pollen dimorphism), during cold-treatment of excised flower buds, in cultured anthers) was studied. In all three routes, P-pollen frequency (premitotic pollen, before 1. sporophytic division, PPF) was affected in essentially the same way. At 24 °C and long days, PPF was low and short days had only a slightly increasing effect. At 18 °C and long days, PPF was higher and short days further increased it. Correlated with PPF under the different growth regimes was the percentage of units with more than one vegetative-type nucleus (normal embryos + abortive embryos + multinucleate pollen) in 3 weeks old anther cultures. Under greenhouse conditions, PPF was generally higher than at 24° in growth rooms and showed a maximum in the winter months. Plant age did not affect PPF. These results give further evidence that pollen embryogenesis is predetermined before excision and culture of the pollen or anthers.