Study on in vitro culture conditions of pollens from four tree species of Catalpa Scop.including Catalpa bungei

Effects of culture time,culture temperature and pH value,sugar and PEG-4000 concentrations in liquid medium on pollens in vitro culture of two Catalpa bungei C.A.Mey.samples(CB-1 and CB-2),C.fargesii Bur.f.duclouxii(Dode) Gilmour,C.speciosa(Warder ex Barney) Engelmann and C.ovata G.Don were studied using pollen germination rate and pollen tube length as indexes in order to select the best in vitro culture conditions of pollen.The results show that culture time has a extremely significant effect on pollen germination rate and pollen tube length of C.bungei.After 6 h of culture,the pollen germination rate reaches its peak(91.0%) and the pollen tube length is the longest after 6-7 h of culture,indicating that the best culture time is 6 h.The culture temperature,pH value,sugar and PEG-4000 concentrations in liquid medium exert obvious influence on pollen germination rate and pollen tube length of the four species.Higher or lower temperature in the range of 19 ℃-36 ℃ has a certain inhibitory effects on pollen germination,and the best culture temperature for all species is 24 ℃-28 ℃.The weak acidic environment is favorable for germination and growth of pollens of the four species,and the suitable pH value of liquid medium ranges from pH 5.0 to pH 5.6.The pollen germination rate and pollen tube length reach their peaks when the sugar concentration is 15-25 g·L-1.Different concentrations of PEG-4000 added in the liquid medium restrain germination and growth of pollens in a short culture time(3 h),but when the culture time is extended to 6 h,addition of 5-25 g·L-1 PEG-4000 promotes pollen germination,in which the proper concentration of PEG-4000 is 20 g·L-1.It is suggested that in vitro culture conditions of pollens of different species or even different provenances are not the same,and appropriate adjustments should be done.