Considering the preferences for nitrogen forms by invasive plants: a case study from a hydroponic culture experiment

Although preference for NH₄⁺, NO₃^? or a combination of the two often differs among species, we know little about the responses of invasive plants to different inorganic N forms. Furthermore, many studies have suggested that an increase in N availability may facilitate further invasions. However, most of these studies predicted the positive feedback without considering the preference for N forms of invasive plants. Therefore, we cultivated four common invasive species (Mikania micrantha, Ipomoea cairica, Wedelia trilobata and Bidens pilosa) in South China with hydroponic media containing different forms of N (i.e. NO₃^?, NH₄NO₃ and NH₄⁺) at equimolar concentrations. Our results showed that the N forms significantly affected the growth, biomass allocation and physiological traits of the plants. All four invasive plants supplied with NO₃^? alone had better performance and greater allocation to root biomass than did plants that were supplied with NH₄⁺ alone. Moreover, the photosynthetic rate, pigment content and photosystem II activity of plants supplied with NO₃^? or NH₄NO₃ were significantly higher than those of plants supplied with NH₄⁺alone. The results suggested that all four invasive plants preferred NO₃^? rather than NH₄⁺, and changes in NO₃^? played an important role in furthering the invasions of these plants than did changes in NH₄⁺. Our results implied that decreasing NO₃^? may be a useful tool for controlling and managing invasive plants preferring NO₃^?. In addition, this study highlighted the importance of considering plant N form preference to better understand plant invasions.     

甘薯基因组NBS-LRR类抗病家族基因挖掘与分析

NBS-LRR类基因家族是植物抗病R基因(Resistance gene)数量最多的一类,具有NBS (Nucleotide-binding site)和LRR (Leucine-leucine-repeat)结构域。甘薯(Ipomoea batatas)栽培种基因组已完成测序,但尚未注释,本研究对甘薯基因组序列进行外显子预测,得到甘薯染色体组全基因组蛋白序列,在此基础上进一步对NBS-LRR家族基因鉴定和分析表明,甘薯基因组中含有379个NBS-LRR家族基因,占全基因组基因总数的0.212%,其中N型亚家族120个,NL型103个, CNL型133个, TNL型22个, PN型1个。所有染色体上均有NBS-LRR家族基因分布,但数量明显不同,其中有60.9%的NBS-LRR基因序列呈簇状分布。NBS-LRR基因序列有15个保守结构域,在N端较为保守。研究结果为甘薯进一步开展NBS-LRR家族基因的功能研究和抗性育种提供了参考。     

Inhibitory effect of Ipomoea aquatica extracts on glucose absorption using a perfused rat intestinal preparation

Investigations were carried out to evaluate the effect of Ipomoea aquatica aqueous and dichloromethane/methanol extracts on the glucose absorption using a rat intestinal preparation in situ. Extracts orally tested at the dose of 160 mg/kg exerted a significant inhibitory effect on glucose absorption when compared with control animals. The most pronounced effect was observed with the aqueous extract. Ouabain used as reference inhibitor strongly inhibited glucose absorption. On the other hand both plant extracts inhibited the gastrointestinal motility suggesting that the inhibition of glucose absorption is not due to the acceleration of intestinal transit.     

甘薯台龟甲对五爪金龙的取食力测定

试验结果表明,甘薯台龟甲幼虫对五爪金龙具有较强的取食力,取食力随着虫口密度的增加而增强。幼虫期的取食力(y)和投放1龄幼虫密度(x)的线性关系式为y=19.32+11.36x。每个叶片投放1龄幼虫2头,8d后取食力可达100%。甘薯台龟甲成虫对五爪金龙的取食力更为显著,每叶放虫1头,6d后取食量达100%,且取食力随着虫口密度的上升而提高。放虫后6d的取食力和成虫密度的对数关系式为y=51.09+120.67logx。成虫的投放密度达到1头/叶,6d后叶片就能100%被取食。     

不同生境对五爪金龙部分生理指标的影响

五爪金龙Ipomoea cairica(L.)Sweet是南方广大地区危害严重的入侵杂草之一。采用电导率法和分光光度法,测定了5个不同的自然生境中五爪金龙的相对电导率和叶绿素含量等生理指标,并进行方差分析。结果表明:不同生境中,五爪金龙的质膜透性之间的差异部分达到显著水平;除了生境4、5之间外,其叶绿素a、b及总含量均达到极显著水平。     

沼泽红假单胞菌的分离鉴定及对蕹菜生长的影响

从引进的日本土壤改良剂中富集分离得到1株光合细菌,通过形态学观察及生理生化特性鉴定,鉴定为该菌株属于红假单胞菌属。以泰国柳叶蕹菜为试验材料,用GRH-507菌液稀释500倍在蕹菜幼苗期、生长期进行叶面喷施,以等量的清水作对照,在成熟期调查蕹菜的产量。结果表明,喷施500倍GRH-507菌液稀释液能提高蕹菜的产量,两次收割产量分别比对照增产31.03%、20.74%。     

现代生物技术在甘薯育种中的应用

现代生物技术攻克了过去在甘薯(Ipomoea batatas)育种中无法解决的难题。诱变育种、细胞工程、分子标记和基因工程等现代生物技术已在甘薯选育、品质改良、增强抗病虫性等方面上发挥了非常重要的作用。综述了诱变育种、细胞工程、分子标记和基因工程等现代生物技术在甘薯育种中的研究与利用概况。     

Interaction of plant genotype and management in the persistence of a perennial grass exposed to grazing and soil fertility stresses

Increased stocking rates under typical pasture improvement practices in southern Australia have often been associated with low persistence by sown perennial grasses subjected to continuous stocking. Cultivars of the perennial grass phalaris (Phalaris aquatica L.), which is widely used in southern Australia, vary in their phenology and growth habit. Winter‐active cultivars have also been developed with improved stress tolerances, viz. heavy grazing pressure (Holdfast GT) and acid soils (Advanced AT). This study examined the persistence of phalaris genotypes over 4 years under five management treatments: high P‐high stocking rate (18 sheep per hectare) rotationally stocked (HPRS); high P‐high stocking rate continuously stocked (HPCS); high P‐intermediate stocking rate (13·5 sheep per hectare) continuously stocked (HPCS13.5); low P‐low stocking rate (9 sheep per hectare) rotationally stocked (LPRS); and low P‐low stocking rate continuously stocked (LPCS). Basal frequency of phalaris declined rapidly under HPCS and LPCS in the first year of treatments when periods of low herbage mass occurred under low rainfall. Basal frequency in high P treatments stabilized and partially recovered but continued to decline in low P treatments. Holdfast GT survived the early decline in the HPCS treatment better than other winter‐active cultivars and similar to a known grazing tolerant, semi‐winter‐dormant cultivar. Advanced AT and older winter‐active cultivars were sensitive to continuous stocking but persisted better under rotational stocking or under a reduced rate of continuous stocking (HPCS13.5). Rotational management clearly promoted persistence of winter‐active phalaris, but long‐term persistence will be better ensured by combining management with the use of genotypes with grazing tolerance traits.     

厚藤种子萌发特性

 以厚藤Ipomoea pes-caprae种子为试验材料，测定其种子的大小、千粒质量、硬实率、生活力以及在不同处理条件下的发芽势和发芽率。结果表明：机械处理下的效果最好，其种子平均发芽势和发芽率均提高到95.3%；其次为980 g·kg^－1硫酸处理90 min较好，平均发芽势达到91.2%，发芽率达93.5%；氢氧化钠处理也可明显提高厚藤种子萌发能力，400 g·kg^－1氢氧化钠处理36 h的平均发芽率可达79.4%；不同温度处理以25 ~ 30 ℃的萌发能力最强，其发芽势为24.6%，发芽率为43.4%。实际工作中，可以采用机械处理或酸碱处理的方法以提高厚藤种子的萌发能力。图2表4参18     

自发性气调对鲜切茭白品质及微生物的影响

[目的]研究不同气调包装材料对鲜切茭白品质及表面微生物的影响。[方法]将茭白鲜切处理,置于不同材料的塑料袋包装中,在0~4℃进行自发性气调贮藏,定期检测茭白的色泽、失重率、硬度、电导率、可溶性固形物、还原糖、总糖、酸度以及菌落总数和乳酸菌数。[结果]试验表明,贮藏6 d时,3种包装材料对茭白的色泽、失重率,固形物含量变化都有一定的延缓作用;贮藏12 d时,所有处理组茭白的电导率均小于对照组;贮藏16 d时,聚丙烯、高密度聚乙烯包装鲜切茭白硬度低于对照,高密度聚乙烯包装袋茭白还原糖高于对照组,低密度聚乙烯包装袋内茭白总糖高于对照组,所有处理组茭白总酸度均低于对照组;贮藏至22 d时,所有处理组茭白表面的菌落总数和乳酸菌数均少于对照组。[结论]高密度聚乙烯、低密度聚乙烯及聚丙烯包装材料对鲜切茭白均有延长保藏期的作用,但也存在差异,自发性气调贮藏对鲜切茭白有延长保质期的作用。