【作者】 陈贵林；

【导师】 李式军；

【作者基本信息】 南京农业大学 ， 蔬菜学， 1996， 博士

【摘要】 不结球白菜(Brassica campestrisssp. chinensis(L.)Makino)是我国南方必需周年供应的重要蔬菜,近来来北移面积迅速增加,并为欧、美、日等国广泛引种,逐渐成为一种世界性蔬菜。病虫严重、越夏困难是不结球白菜的主要生产障碍。采用无土栽培技术是有效解决途径之一。但很易出现失绿黄化现象,制约了无土栽培的发展。同时,不结球白菜北移栽培中也常发生失绿黄化现象。铁是无土栽培营养液单一元素成本最高(占不结球白菜营养液总成本的近1/2)的营养元素,也是最易发生营养失调的营养元素。选育可供生产应用的耐低铁品种是解决不结球白菜上述难题的有效途径。本研究利用我校丰富的不结球白菜品种资源进行了耐低铁基因型的筛选,并在此基础上进行了耐低铁机理的探讨,为解决不结球白菜缺铁失绿症和提供低成本高效益无土栽培营养液配方提供理论依据,并丰富双子叶植物耐缺铁机理的理论研究。 1.本研究采用无土栽培方法,以缺铁的Hoagland Ⅰ配方为基本营养液,对来自我国不同生态区的40份不结球白菜品种进行了连续2期耐低铁基因型筛选,首次证明不结球白菜中存在广泛的铁营养基因型差异。通过对缺铁失绿指数、叶绿素含量、生长量等筛选指标的综合评价,筛选出“东台百合头”(DTBHT)和“无锡三月白”(SYB)两份耐低铁胁迫的珍贵资源。而“黄心乌”(HXW)和“莲坂油菜”(LBYC)为缺铁高度敏感基因型。 同时,本研究结果还表明,在正常供铁情况下不结球白菜存在富铁能力的基因型差异。在营养液铁浓度为3mg/L条件下,供试品种“马耳头”(MET)含铁量高达295μg/gDW,而“白叶四月慢”(BYSYM)只有90μg/gDW,二者相差达二倍以上。本结果为通过育种手段和水培方法生产高富铁蔬菜,来改善我国居民铁营养状况,提供了珍贵基因型和新途径。 2.采用2个不结球白菜基因型,培养在Fe浓度为1.0、5.0、15.0、50.0mg/L的完全营养液中,研究了介质铁浓度对幼苗干物重和体内Fe、Mn、Cu、Zn含量的影响,结果表明:2品种对Fe营养的需求明显不同,DTBHT较HXW能忍耐较低浓度的Fe,其最适生长介质Fe浓度也显著低于HXW,DTBHT在浓度为5.0mg/L时干物质积累量即达最大,而HXW即在Fe浓度为15.0mg/L时为最大。低铁浓度下DTBHT铁利用效率明显高于HXW,高浓度Fe(50mg/L)明显抑制2品种的生长,并产生轻度毒害现象。不同供铁浓度下(1—15mg/L),随着介质铁浓度的升高DTBHT和HXW根系和老叶中Mn、Cu、Zn含量也随之降低。而当介质Fe浓度达50mg/L时植株中Mn、Cu、Zn含量又有升高,2个品种间是有差异的,尤其是Zn含量,无论根系、新叶还是老叶,DTBHT的含锌量均低于HXW。本试验从铁营养利用角度验证了DTBHT较HXW具有较高的铁利用效率,说明我们所进行上述的耐缺铁筛选指标可靠,高富铁蔬菜的选育和生产首先应利用富铁基因型,在此基础上再从适度增加分质铁浓度来考虑。更多还原

【Abstract】 Pak- choi ( Brassica campestrisssp. chinensis (L. ) Makino) is very important and necessary in the vegetable supplement in south China, and gradually planted in north China recently. It becomes a kind of world - wide vegetables growing extensively in Europe, America and Japan etc. The most serious problem during the pak —choi cultivation is diseases and insect pests, and it’s difficult to grow well in hot summer. Soilless culture of pak—choi is one of effective way to overcome these problems, with the limited factor of Fe-chlorosis. Meanwhile, Fe—chlorosis appears when pak—choi grows in north China. EDTA—Fe is the most expensive element of soilless nutrition input. And Fe also is the nutrient element which causes nutrient inbalance easily. It’s effective to work out these problems through the breeding of Fe—deficiency resistant genotypes which can be used in the production. Selection of Fe—deficiency resistant genotypes and the study of mechanisms were carried out in this experiment. Research will enrich the knowledge of Fe-deficiency resistance dicots and serve as scientific guide for pak —choi soilless culture.1. Continuous two times selections were carried out in 40 varieties pak —choi which are from different ecoarea under low Fe Hoagland I soilless nutrient solution. The results showed that Fe—deficiency resistant ability varied significantly among different pak —choi genotypes. Using Fe—chlorosis index, chlorophyll content and growth weight etc as selection parameters, DTBHT and SYB are two precious Fe—stress resistant varieties. While HXW, LBYC and LBY are very sensitive ones.Fe—content differed significatly among various genotypes under normal Fe supply. Fe content of MET is more than 3 times higher than BYSYM under 3 mg/’L Fe3+ nutriton, the former is 295 μg/gDW, the later is 90μg/gDW. The results is useful in supply ing valuable genotyes and new methods to improve the popular Fe — nutrition through breeding and soilless culture to produce vegetables of high Fe nutrition.2. Two pak —choi genotypes were cultured in complete nutrition solution at different Fe levels of 1. 0, 5. 0, 15. 0, 50.0mg/L to study the effects of Fe contents on seedling growth and plant Fe, Mn, Zn, Cu contents, Fe requirements of the two genotypes varied greatly. DTBHT was more tolerate to low Fe level. The optimal Fe contents for dry weight accumulation was 5. 0mg/L and 15. 0mg/L respectively. Fe efficiency of DTBHT is greatly higher than HXW under low Fe levels. High concentration of Fe (50mg/L) greatly inhibited growth of the two genotypes, and induced slightly poisonous injury, Mn, Cu, Zn contents of roots and older leaves decreased when Fe concentration was increased to 50mg/L. The response of the two genotypes varied in this respect, especially, Zn content of DTBHT was lower than that of HXW. It’s proved that Fe efficiency of DTBHT is higher than that of HXW. And the selection parameters are reliable. Breeding and production of high Fe content vegetables should begin with the genotypes of high Fe content and increase the Fe content of nutrition later.3. Response of 4 different Fe stress sensitive genotypes to Fe stress. The results showed that pH of these 4 genotypes growth medium increased after Fe stress, but was lower than Fe—suply treatment. Acidity increas caused by pak—choi root system activity was weak when the NO3- used as the only nitrogen resource. Peak period of root cytoplasm membrane Fe3+ reduction capicity appears on the sixth day after Fe — dificiency treatment, that of DTBHT and SYB, which were tolerant to low Fe were much higher than that of HXW and LBYC, which were sensitive to low Fe. Chlorophyll of upper most expanded leaves of these 4 pak — choi genotypes decreased significantly under Fe stress, the effect being smaller in Fe—stress resistant genotypes than in sensitive ones. Fe content genotypes than of upper most expanded leaves of DTBHT is much higher than that of LBYC, So, DTBHT has higher Fe efficiency.4. Diural change of Fe3+ reduction capacity under different light regimes treatment was carried out on different Fe — stress sensitive pak — choi genotypes. The results showed that Fe3+ reduction capacity in the root of Fe — difiency resistant genotypes changes diurnally since the sixth day after Fe stress treatment under normal light regime (14h light/10h dark) Fe3+ reduction capacity decreased in the dark and increased under light, and reached the highest Fe3+ reduction capacity 4—6h after lighted. In contrast, reduction capacity of Fe—deficiency sensitive genotype changed irrgularly. There was little difference of root Fe3+ reduction capacity amony different genotypes in Fe supply treatmen under normal light regimes. Diurnal changes of Fe3+ reduction capacity of Fe — dificiency resistant genotypes can be broken through continous light. It’s the first time that such a law was proved in pak -choi Stevens also found the similar law in soybean in 1994. So, it’s possible the Fe absorption of plant not changes diurally. It’s inportant intheory and practice in the management in soilless nutrition and the selection of Fe—deficiency resistant genotypes vising reduction capacity as parameter.5. Effects of different Fe—supply on seedling Fe, Mn, Cu and Zn contents of Fe di-ficiency—sensitive genotypes including DYBHT and LBYC- Fe—stress significantly lowered leaf Fe content, the effect being greater in new leaves than in older ones. Fe efficiency of DTBHT was higher than LBYC in Fe—stress and Fe—supply treatments. While root Fe content of DTBHT was greatly higher than LBYC in the case of Fe—supply, it become similar in Fe—stress treatment. From the results it can be concluded that roots of DTBHT have higher Fe absorbance and transportation efficiency than LBYC under Fe stress condition. Under Fe stress, Mn, Cu, Zn contents of leaves increased greatly and Mil contents of roots decreased in the two genotypes tested DTBHT showed higher Mn enriching abiolity than LBYC So, the difference of Fe using efficiency of pak—choi under Fe stress was determined by its genetic background.6. Two Fe — deficiency resistant genotypes and two ssensitive ones were selected fristly, and the genotypic difference of Fe nutrition was proved in this experiment. These are the base of the further theoretical research and high Fe—content genotypies. Fe3+ reduction capaticy of different Fe stress sensitive genotypes changed diurally, it’s more obvious in Fe deficiency resistant genotypes. The results filled the gaps in fields of such research. Root system of pak—choi absorbed Fe, Cu, Mn, Zn competively or coorperative-ly- The research enriched the knowledge of Fe deficiency resistance dicots and found a new way to overcome Fe chlorosis and reduce the cost of soilless nutrition.更多还原