Light quanta modulated characteristics of Ni uptake by Brassica juncea seedlings: the interdependence of plant metal concentration and biomass

The relationships between the concentration of metal in the growth medium, Cs, the concentration of metal absorbed by the plant, Cp, and the total biomass achieved, M, all of which are factors relevant to the efficiency of metal uptake and tolerance by the plant, have been investigated via the physiological response of Brassica juncea seedlings to Ni stress. The factorial growth experiments treated the Ni concentration in agar medium and the diurnal light quanta as independently variable parameters. Observations included the evidence of light enhancement of Ni toxicity in the root, as well as at the whole-plant level. The shoot mass index possibly is an indicator of the amount of shoot metal sequestration in B. juncea, as are the logarithmic variation of Cp with Cs and the power-law dependence of M on Cp. The sum total of these observations indicates that, for the Ni accumulating plant B. juncea, the overall metabolic allocation to either growth or metal tolerance of the plant is important. Neither a rapid biomass increase nor a high metal absorbed concentration favored the removal of high metal mass from the medium. Rather, the plants with a moderate rate of biomass growth and a moderate absorbed metal concentration demonstrated the ability to remove the maximum mass of metal from the medium. The implication of these results as related to the extant model of phyoextraction efficiency is discussed.     

Chromosome Numbers of Brassiceae (Cruciferae) in China

Reported in this paper are chromosome numbers of 41 species and varieties of Brassiceae in China, belonging to 5 genera. The chromosome numbers of 15 Species and varieties are first reported and some problems concerning chromosome numbers of Brassiceae are also discussed.     

甘蓝型油菜和芥菜型油菜种间杂交研究

甘蓝型油菜与芥菜型油菜杂交研究结果表明,杂交结实力与杂交组合方式以及参与杂交的亲本材料有关,以芥菜型油菜作母本的杂交结实力高于以甘蓝型作母本的组合：芥×甘杂交组合的平均结实数／花为 ２．６４ 粒,而甘×芥杂交组合的平均结实数／花为 ０．１０ 粒。芥甘杂种一代形态特征和生育期介于双亲之间,甘芥杂种一代不表现整齐的中间类型,株间差异明显;总体来看,芥甘杂种一代与双亲回交的结实力（０．４０,０．２１）低于甘芥杂种一代与双亲回交的结实力（３．３０,１．７４）,无论是芥甘杂种一代还是甘芥杂种一代,用甘蓝型油菜作父本回交的结实力高于用芥菜型油菜作父本回交的结实力,但也有个别回交组合出现例外,不表现上述规律。 Ｂ Ｃ１ 代种子当年播种出苗率低（１８．５％ ）,群体株间性状差异明显,生育期极不一致。芥甘杂种一代与甘蓝型油菜亲本第二次回交,其平均结实数／花较回交一代提高 １．０８ 粒, Ｂ Ｃ２ 代种子当年播种出苗率仍较低,但较对应的 Ｂ Ｃ１ 代稍有提高,群体中出现趋回交父本性状但雄性育性彻底退化的植株。芥甘杂种一代自由授粉所得 Ｆ２ 群体是一个变异极为丰富的遗传群体。     

Effects of competition,litter, and disturbance on an annual carnivorous plant (Utricularia juncea)

The effects of removal of live plants and litter (using herbicide, clipping, and raking) on seedling establishment were examined in Utricularia juncea (bladderwort), an annual carnivorous plant of low frequency in wet, nutrient-poor pine savannas of the southeastern United States. In addition, the spatial distribution of this species in relation to crayfish disturbances was determined. The creation of competition-free gaps in the groundcover canopy in May 1996 (using herbicide) promoted establishment of this species at two sites by September 1997. Standing dead and litter left in herbicide-treated plots inhibited establishment. Density was near zero in undisturbed plots. Natural occurrences of this species were associated with crayfish mounds, which bury plant litter as they erode and increase in area. These results suggest that Utricularia juncea is a fugitive species that depends on disturbances or litter-free microsites to become established in wet, nutrient-poor seepage savannas in southern Mississippi. It is hypothesized that the production of carnivorous traps combined with relatively high allocation to reproductive structures (>90%) and the production of a persistent seed bank make it well-adapted to nutrient-poor and disturbed habitats.     

酶联免疫吸附法（ELISA）检测四川“榨菜”病毒种类

1990至1991年在“榨菜”病毒病发生的始期和盛期,从四川九个县(市)近郊、远郊采集样品492份,用TuMV、CMV、TMV、PVX、PVY和CaMV六种抗血清,经酶联免疫吸附间接法进行检测,属于TuMV和TuMV与其它五种病毒之一或之二复合感染的有422份,占总样品数的85.77％,其中由TuMV单一感染的305份,占61.99％。此外,还有PVX、PVY、CaMV单一感染病样27份,占5.49％,而情况不明的43份,占8.74％,总检出率91.26％。检测结果表明,发病始期或盛期,近郊或远郊均以TuMV和TuMV与CMV复合感染的病毒为主,是四川“榨菜”生产上主要的病毒种类。     

Chlorophyllase and peroxidase activity during degreening of maturing canola (Brassica napus) and mustard (Brassica juncea) seed

Chlorophyllase and peroxidase activities were measured in relation to seed maturation and degreening in canola ( Brassica napus cvs Westar and Alto) and mustard ( Brassica juncea cvs Cutlass and Lethbridge 22A). Samples of seed collected at the same moisture content were pooled, then divided and used for each assay. During maturation the green pigment (chlorophyll and related pigments) content of canola seed decreased linearly and was lower than that measured in mustard at all moisture contents studied, except for the highest and lowest moisture contents. Chlorophyllides and pheophorbides were detected in canola and were essentially absent in mustard. This difference in accumulation of dephytylated pigments infers differences in the pigment degradation pathways in Brassica species. Interspecific differences in the enzymology of degreening were found. Green pigment degradation was associated with increased chlorophyllase activity and low peroxidase activity in canola and low Chlorophyllase and high perosidase activity in mustard. The possible role of ethylene in seed degreening is discussed.     

Effect of nitrogen on carbonic anhydrase activity, stomatal conductance, net photosynthetic rate and yield of mustard

Mustard (Brassica juncea L.) cv. Rohini was grown under three levels of urea nitrogen fertilization [0, 2, and 4 g(N) pot^-1]. Carbonic anhydrase activity and net photosynthetic rate in leaves of 50 d-old plants as well as yield attributes at harvest increased with increasing levels of nitrogen. Stomatal conductance was not affected, and oil content decreased. This revised version was published online in June 2006 with corrections to the Cover Date.     

Transport and Partitioning of Lead in Indian Mustard (Brassica juncea) and Wheat (Triticum aestivum)

Lead (Pb) contamination in soils is a serious concern because it can be taken up by crops and then transferred through the food chain, posing a potential risk to human health. Indian mustard (Brassica juncea) and wheat (Triticum aestivum) are important crop species known to accumulate heavy metals in their tissues. This study aimed at understanding the transport and accumulation of Pb in these two species and the risk associated with consumption of these foods, which would help us in mitigating accumulation of Pb in edible tissues. The plants were grown at different Pb concentrations for the entire life cycle, and the partitioning of the metal to different tissues was examined. The results showed that plant species differ widely in their ability to transport and accumulate Pb in different tissues. In B. juncea, there was significant accumulation of Pb in both siliques and seeds, whereas most of the Pb in wheat was concentrated in the vegetative tissues and less to the flag leaf and reproductive tissues. In both species, although seed Pb concentrations exceeded acceptable limits, dietary intake did not exceed acceptable limits in most treatments, indicating that more studies on Pb transport and redistribution in crop species is necessary.     

Overexpression of Brassica juncea wild-type and mutant HMG-CoA synthase 1 in Arabidopsis up-regulates genes in sterol biosynthesis and enhances sterol production and stress tolerance

Brassica juncea 3-hydroxy-3-methylglutaryl-CoA synthase (HMGS) is encoded by four isogenes (BjHMGS1-BjHMGS4). In vitro enzyme assays had indicated that the recombinant BjHMGS1 H188N mutant lacked substrate inhibition by acetoacetyl-CoA (AcAc-CoA) and showed 8-fold decreased enzyme activity. The S359A mutant demonstrated 10-fold higher activity, while the H188N/S359A double mutant displayed a 10-fold increased enzyme activity and lacked inhibition by AcAc-CoA. Here, wild-type and mutant BjHMGS1 were overexpressed in Arabidopsis to examine their effects in planta. The expression of selected genes in isoprenoid biosynthesis, isoprenoid content, seed germination and stress tolerance was analysed in HMGS overexpressors (OEs). Those mRNAs encoding enzymes 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR), sterol methyltransferase 2 (SMT2), delta-24 sterol reductase (DWF1), C-22 sterol desaturase (CYP710A1) and brassinosteroid-6-oxidase 2 (BR6OX2) were up-regulated in HMGS-OEs. The total sterol content in leaves and seedlings of OE-wtBjHMGS1, OE-S359A and OE-H188N/S359A was significantly higher than OE-H188N. HMGS-OE seeds germinated earlier than wild-type and vector-transformed controls. HMGS-OEs further displayed reduced hydrogen peroxide (H(2) O(2) )-induced cell death and constitutive expression of salicylic acid (SA)-dependent pathogenesis-related genes (PR1, PR2 and PR5), resulting in an increased resistance to Botrytis cinerea, with OE-S359A showing the highest and OE-H188N the lowest tolerance. These results suggest that overexpression of HMGS up-regulates HMGR, SMT2, DWF1, CYP710A1 and BR6OX2, leading to enhanced sterol content and stress tolerance in Arabidopsis.     

陕北黄芥芥酸含量的主基因+多基因遗传分析

以吴旗黄芥×长安芥菜组合的6个世代P1、P2、F1、B1、B2和F2群体为材料,利用植物数量性状主基因+多基因模型的多世代联合分析方法研究了该组合芥酸含量的遗传特征.结果表明:吴旗黄芥×长安芥菜组合芥酸含量受2对加性-显性-上位性主基因+加性-显性-上位性多基因(E模型)控制.主基因效应中,加性效应大于显性效应,第一对主基因加性效应(da)和显性效应(ha)分别为-4.718 0和4.419 5;第二对主基因的加性效应(db)和显性效应(hb)分别-4.005 8和2.023 7;2对主基因对芥酸含量的贡献差异较大,第二对主基因加性和显性效应之和占第一对主基因加性和显性效应之和的65.98%;2对主基因间存在一定的互作效应(绝对值在0.338 7～3.694 1),其中第一对主基因显性×第二对主基因加性效应(jba)较大,为3.694 1.B1、B2和F2群体芥酸含量主基因遗传率分别为68.83%、44.76%和87.99%;多基因遗传率分别为20.29%、41.21%和0,F2代表现出较高的遗传力,可在早期世代对芥酸含量进行选择.