难栽培食用菌原生质体融合技术研究进展     

邹莉  孟雪  李绍鹏 《黑龙江农业科学》2006,(2):67-69

大多数难栽培食用菌都与植物有共生或寄生关系,人工栽培出菇问题一直无法解决.原生质体融合技术是近几年来迅速发展起来的细胞工程育种技术,它去除了细胞壁的屏障,实现了远缘杂交,为难栽培食用菌育种提供了新方法.本文着重介绍了难栽培食用菌原生质体融合技术,并概括了其发展前景.  相似文献   

民营中小企业融资问题探讨     

庄胡蝶 《安徽农业大学学报》2007,(4):25-27,139

改革开放至今, 民营中小企业经过长足的发展, 己经成为国民经济的重要组成部分, 中国经济持续、快速发展的动力之源。但融资难已成为制约中小企业、尤其是民营中小企业发展的瓶颈。本文从企业、金融、政府等三个角度对中小企业融资难的成因进行了分析, 在此基础上提出了相应的对策建议。  相似文献   

我国一些土壤中较难提取的固定态铵     

CHEN Bi-Yun  CHENG Li-Li  WEN Qi-Xiao 《土壤圈》1999,9(2):185-188

Ninety-three soil samples and 19 sedimentary rock samples collected from 21 provinces of China were analyzed for their contents of fixed ammonium and total N by Kjeldahl-HF method. Results showed that amount of difficultly extractable fixed ammonium (the fixed ammonium that is not determinable by Kjeldahl procedures commonly used for soils) in soils ranged from 0 to 202 mg kg^-1. It was generally more than 50 mg kg^-1 in soils in Changji and Turpan districts, Xinjiang, accounting for 3.2%~36.8% with an average of 13.9% of the total N. For some Orthents derived from purple shale and purple sandstone in Sichuan and Hunan provinces and Chao soils derived from secondary loess in Henan Province and Ningxia Autonomous Region it was generally around 30 mg kg^-1, accounting for 4%~7% of the total soil N, and for most of the rest of soils studied, with the exception of some subsoils, no or trace difficultly extractable fixed ammonium could be detected. It was suggested that the difficultly extractable fixed ammonium was originated from parent rock, and for slightly weathered soils derived from parent materials rich in this form of N the Kjeldahl method might give underestimation of total soil N.  相似文献