温度、光照和水分对飞扬草种子萌发和幼苗生长的影响

为明确热带常见杂草飞扬草(Euphorbia hirta)的种子萌发特性,本研究运用培养皿滤纸法和盆栽法,分别研究温度、光照和水分条件对飞扬草种子萌发和幼苗生长的影响。结果表明,飞扬草种子在20~40℃范围内均可萌发,其中30℃为种子萌发的最适温度(萌发率和萌发指数均最大),25℃时幼苗生长最好(根长/苗长为1.031)。恒温条件(25℃)下,光照8~24h时的种子萌发率无显著差异(平均值94.07%)、光/暗0h/24h时萌发率降至52%(P0.05),萌发指数随光照时间缩短先增大后降低,光/暗16h/8h时最大(93.93),0h/24h最低(30.59);有光照时幼苗的根长均显著大于苗长,无光照时苗长显著大于根长(P0.05)。变温条件(光/暗,35℃/25℃)下,光照时长对飞扬草种子萌发率和幼苗苗长无显著影响(P0.05),随光照时长缩短萌发指数和幼苗根长均显著减低(P0.05)。综合各指标,12~16h光照为飞扬草种子萌发和幼苗生长的最佳光照条件。25℃、光/暗12h/12h条件下,飞扬草在土壤最大持水量60%时的种子出苗率达39%、幼苗根长苗长比为1.10∶1。

Effect of temperature,light length and water condition on Euphorbia hirta germination and seedling growth

To examine germination characteristics of the common weed Euphorbia hirta in tropical farmland and forest land, we studied the effects of temperature, light and water conditions on germination and seedling growth of E.hirta using petri-dish and pot-culture methods.The results showed that E.hirta seeds germinated between 20~40 ℃;the optimum germination temperature was 30 ℃, where germination rate and germination index were the highest.The optimum temperature for seedling growth was 25 ℃, where the root∶shoot ratio was 1.03∶1.Under constant temperature (25 ℃), there was no significant difference among seed germination rates with light length of 8-24 h (the average value was 94.07%);germination rate was reduced to 52% at 0 h/24 h (light/dark, L/D).The germination index first increased and then declined with shortened light length, with a maximal value of 93.93 at 16 h/8 h (L/D) and minimal value of 30.59 at 0 h/24 h (L/D).Seedling root lengths were markedly longer than shoot lengths with light and the opposite without light (P<0.05).Under fluctuating temperature conditions (L/D:35 ℃/25 ℃), seed germination rate and seedling shoot length had no significant change (P>0.05), but germination index and seedling root length were significantly decreased with shortened light length (P<0.05).We concluded that light length of 12-16 h was the optimum light condition.Optimum seed germination and seedling growth of E.hirta occurred when soil moisture was 60% of the maximum water-holding capacity at 25 ℃ with 12 h/12 h (L/D), where emergence rate and root:shoot ratio were 39.38% and 1.10∶1, respectively.