Tissue culture tools for selenium hyperaccumulator Neptunia amplexicaulis for development in phytoextraction

Neptunia amplexicaulis is an herbaceous legume endemic to the Richmond area in central Queensland,Australia and is one of the strongest known Selenium hyperaccumulators on earth,showing significant potential to be utilised in Se phytoextraction applications.Here a protocol was established for in vitro micropropagation of Se hyperaccumula-tor N.amplexicaulis using nodal segments from in vitro-germinated seedlings.Shoot multiplication was achieved on Murashige and Skoog(MS)basal media supplemented with various concentrations of 6-Benzylaminopurine(BA)(1.0,2.0,3.0 mg L^(−1))alone or in combination with low levels of Naphthaleneacetic acid(NAA)(0.1,0.2,0.3 mg L^(−1)),with 2.0 mg L^(−1) BA+0.2 mg L^(−1) NAA found to be most effective.Elongated shoots were rooted in vitro using NAA,with highest root induction rate of 30%observed at 0.2 mg L^(−1) NAA.About 95%of the in vitro rooted shoots survived acclimatization.Clonally propagated plantlets were dosed with selenate/selenite solution and assessed for Se tissue concentrations using Inductively Coupled Plasma Atomic Emission Spectroscopy(ICP-AES)and found to retain their ability to hyperaccumulate.The protocol developed for this study has potential to be optimised for generating clonal plants of N.amplexicaulis for use in research and phytoextraction industry applications.

水稻与水合欢间作对作物群体产量、氮素吸收及土壤氮素的影响

豆科与禾本科作物间作有利于提高氮素利用率及作物群体产量。旱地条件下豆科与禾本科作物间作产量优势的研究已多见报道,但水田环境下水稻(Oryza sativa)与豆科水生作物间作模式的研究报道甚少。在华南地区水田条件下分别构建了2015年晚稻和2015年早稻水稻与水合欢(Neptunia olerace)间作模式,并探讨该模式对产量和稻田土壤氮素的影响。试验设常规施氮水稻单作(N 180 kg·hm^(-2),CK)、低氮水稻单作(N 140 kg·hm^(-2),LRM)、水稻-水合欢间作(N140 kg·hm^(-2),LRN)和水合欢单作(N 140 kg·hm^(-2),NOM)4种处理,测定不同种植模式下的作物产量、吸氮量、土地当量比及稻田土壤全氮含量的变化。结果表明,间作栽培模式下的水稻茎蘖数、叶面积指数和地上部生物量均显著高于CK和LRM,其中与水合欢相邻的边行水稻茎蘖数、叶面积、地上部生物量和产量均显著高于内行。水稻实地面积产量表现为LRN>CK>LRM,LRN处理下水合欢实地面积产量低于NOM。2014年晚稻和2015年早稻,以LRN、NOM和CK计算的土地当量比分别为1.01和1.20,以LRN、NOM和LRM计算的土地当量比分别为1.12和1.25,表明间作模式下作物整体产量明显提高。LRN处理下水稻群体总吸氮量显著低于CK和LRM,经过两季种植后,LRN处理下土壤全氮含量分别比CK和LRM提高了0.21%和1.69%。在水田环境中,水稻与水合欢间作在低氮投入下能维持较高的土地当量比,且提高了作物群体产量和土壤全氮。

四氢嘧啶高产菌株的筛选及发酵条件的优化

目的人工诱变选育高产四氢嘧啶的菌株。方法以海神盐单胞菌Halomonas neptunia ATCC BAA-805为出发菌株,采用紫外线和亚硝基胍复合诱变处理,获得四氢嘧啶产量提高突变株,采用单因素实验优化发酵培养基及发酵条件,进一步提高突变株的四氢嘧啶产量。结果 Halomonas neptunia ATCC BAA-805经复合诱变处理,获得突变株UN-2,摇瓶发酵四氢嘧啶产量达1.8 g/L,与出发菌株相比产量提高了53.8%。单因素优化实验结果为UN-2菌株在酵母粉浓度4.0 g/L,葡萄糖浓度20 g/L,氯化钠浓度7%(w/v),p H 7.5条件下,四氢嘧啶产量为5.53 g/L。结论本研究诱变选育的菌种是适于商业化生产四氢嘧啶的优良菌株。