桑蚕尿素添食对产丝的效应及其机理

在五龄期每日1次叶面添食尿素氮,保留在熟蚕体内的尿素氮量为添加量的22—36%,蚕粪中回收为25—33%,剩桑中11%左右,25—30%没有回收到,可能以NO、NO_2等气态形式损失,未能查明。蚕体吸收的尿素氮有60%以上转移到丝腺中,占添加量的15—25%。茧层和丝中的尿素氮量不低于熟蚕丝腺中的量,说明转移到丝腺中的尿素氮已转化为丝素成分,但其贡献低于1%。即使增加添食次数、添食量或结合脲酶处理,也未使尿素氮对丝物质产量的贡献超过3%,所以尿素添食的直接作用不大。五龄期桑蚕对根外追肥标记桑叶的尿素氮的吸收、转移及熟蚕丝腺、茧层和丝中的尿素氮,比同样试验条件下叶面添食的低50%以上。五龄期1次添食的动态试验表明,在添食后一天内,尿素氮除以粪便排出外,还存在着其他损失途径。

EFFECTS OF UREA ADDED TO MULBERRY SILKWORM'S FOOD ON SILK PRODUCTION

The amount of urea-N remained in adult silkworm was 22-36% of the amount applied during the fifth-instar.Recoveries from feces were 25-33%;about 11% was found in the residural mulberry leaves,and 25-30% was not recovered,probably lost in the form of NO or NO2. More than 60% of the urea-N that was absorbed by the silkworm was transported into silkgland.The amount of urea-N remained in silkgland accounted for 15-25% of the applied level.The amount of urea-N in cocoon or silk could be compared with those in silkgland of adult silkworm,indicating that urea-N transported into the silkgland had been transformed to a component of silk fibroin,but the contribution to cocoon and silk fibroin 'was below 1%.It didn't exceed 3% even though the times or the amount of feeding were increased,or the treatment was combined with ure-ase.lt may be concluded that the direct of addition of urea to mulberry silkworm could be negligible. The contribution of urea-N applied on leaves of mulberry tree to output of silkgland,cocoon and silk fibroin also could be negligible.