Starch Mobilization in Ultradried Seed of Maize （Zea mays L.） During Germination

The effects of ultradry storage on the starch mobilization in maize (Zea mays L.) seed after aging were investigated. The results indicated that there were no significant differences in the content of ATP, starch, and soluble sugar, as well as the activity of amylase, between ultradried seeds and seeds stored at -20℃ during germination. These results were consistent with the higher level of vigor of the ultradried seed. Sieve tube introduction of a fluorescence dye (carboxyl fluoresceindiacetate) and laser confocal microscopy were used to study the development of plasmodesmata in the ultradried seeds. The results indicated that plasmodesmata developed well in ultradried seeds. Fluorescence analysis also showed that the fluorescence intensity in the radicle of ultradried seeds was stronger than that in seeds with a higher moisture content. This suggests that ultradry treatment has no adverse effects on the seeds. After seed imbibition, cell orgaelles could be resumed. It is concluded that ultradry seed storage is beneficial for maintaining seed vigor and that starchy mobilization proceeds regularly during germination.     

钙离子参与一氧化氮促进盐胁迫下的玉米种子萌发

0.001～1.0 mmol·L~(-1)一氧化氮(NO)供体硝普钠(SNP)均能提高玉米种子的发芽率,缓解盐胁迫下种子萌发的抑制作用,其中0.1 mmol·L~(-1)SNP的效果最佳。用胞外游离Ca~(2 )螯合剂EGTA、质膜Ca~(2 )通道阻断剂LaCl_3和液泡Ca~(2 )释放抑制剂钌红与0.1 mmol·L~(-1) SNP共处理,均能减弱或抵消SNP促进种子萌发的作用。据此推测,钙离子参与SNP促进盐胁迫下玉米种子萌发的信号转导过程。     

一个与玉米基因表达沉默有关的cDNA片段的克隆及序列分析

利用cDNA-AFLP技术分离了一个与玉米基因表达沉默有关的cDNA片段,Northern杂交分析表明,该基因在Mo17的苗期和雄穗生长锥伸长期都表达,但在Mo17与其亲缘关系较近的另一亲本杂交的F1代中却表现沉默,即表现单亲沉默。同源性分析表明,该克隆片段与GenBank中玉米通用调控因子(GRF)部分区段有98．6％的同源性,与玉米通用调控因子编码的mRNA部分序列有83％的同源性。以上结果表明,基因沉默可能是亲本GRF在F     

Characterization and Fine Mapping of a Necrotic Leaf Mutant in Maize (Zea mays L.)

Maize (Zea mays L.) is a commercially important crop. Its yield can be reduced by mutations in biosynthetic and degradative pathways that cause death. In this paper, we describe the necrotic leaf (nec-t) mutant, which was obtained from an inbred line, 81647. The nec-t mutant plants had yellow leaves with necrotic spots, reduced chlorophyll content, and the etiolated seedlings died under normal growth conditions. Transmission electron microscopy revealed scattered thylakoids, and reduced numbers of grana lamellae and chloroplasts per cell. Histochemical staining suggested that spot formation of nec-t leaves might be due to cell death. Genetic analysis showed that necrosis was caused by the mutation of a recessive locus. Using simple sequence repeat markers, the Nec-t gene was mapped between mmc0111 and bnlg2277 on the short arm of chromosome 2. A total of 1287 individuals with the mutant phenotype from a F₂ population were used for physical mapping. The Nec-t gene was located between markers T31 and H8 within a physical region of 131.7 kb.     

烯效唑浸种对玉米幼苗生长和内源激素含量的影响

烯效唑浸种对玉米苗期叶片和叶鞘伸长生长有抑制作用,且抑制效应随烯效唑浓度的增大而增强,但植株粗壮,叶宽和茎基宽增加,根系增多,根长增加.烯效唑浸种的玉米幼苗中LAA和GA3含量下降,叶鞘中尤为明显;ZT含量则是地上部提高,根中下降,ABA含量提高,植株各器官中(IAA GA3)/ABA比值均下降,IAA/GA3比值均升高,IAA/ZT和GA3/ZT比值则是地上部降低,根中升高.     

不同类型春玉米灌浆期间籽粒中内源激素IAA、GA、ZR、ABA含量的变化

田间种植的高淀粉（‘郑单19’）、高油（‘通油1号’）和普通型（‘吉单209’）春玉米在籽粒灌浆过程中,‘郑单19’的IAA在授粉后28d达到峰值,‘吉单209’和‘通油1号’的峰值出现在35d;在3个杂交种中,‘郑单19’的IAA峰值最大,‘吉单209’次之,‘通油1号’最低;整个籽粒灌浆期间,‘通油1号’和‘吉单209’的GA含量高于‘郑单19’,在灌浆后期,‘通油1号’仍保持较高的GA含量;‘通油1号’ZR含量的峰值最高,直到后期仍保持较高的水平;‘郑单19’在籽粒灌浆前期的ABA含量较低,但在后期的含量较高。     

盐胁迫对玉米耐盐系与盐敏感系苗期几个生理生化指标的影响

对玉米耐盐系和盐敏感系在不同浓度盐胁迫下生理变化研究的结果表明,与盐敏感系相比,玉米耐盐系叶绿素含量高,脯氨酸、MDA含量及组织外渗液的相对电导率低,且变化幅度小。随盐浓度的增加,玉米耐盐系和盐敏感系的SOD、POD活性均先增加后降低,但玉米耐盐系峰值出现较晚。耐盐系的CAT活性明显大于盐敏感系;地上部分Na/K值小于盐敏感系,且增加的幅度小,而地下部分正相反。     

水杨酸对镉胁迫下玉米幼苗质膜透性和保护酶活性的影响

在Cd^2＋胁迫下,添加外源水杨酸（SA）的培养液中生长的玉米幼苗叶中超氧化物歧化酶（SOD）、过氧化物酶（POD）和过氧化氢酶（CAT）的活性均提高,质膜透性降低,丙二醛（MDA）的积累减少,显示SA对Cd^2＋胁迫具有一定的缓解效应。     

Light-dependent Proton Excretion of Wheat (Triticum aestivum L.) and Maize (Zea mays L.) Roots

We investigated the change of root net proton excretion of seedlings of Triticum aestivum L. and Zea mays L. with daily variation of illumination using a multi-channel pH-stat system. We found an increase of net proton excretion during darkness and a drop after the beginning of illumination. Inhibition of carotenoid biosynthesis by norflurazone and photooxidation of chlorophylls did not change the periodicity or its induction. The induction of diurnal periodicity was possible with blue, green and red light. After induction the oscillation of net proton excretion continued for at least two cycles under constant light. We conclude that net H⁺ excretion of wheat and maize roots may be regulated by an endogenous clock or by a signal from the leaves. The nature of such a hypothetical signal remains unknown.     

超干贮藏榆树种子萌发过程中ATP和可溶性糖含量的变化

经过超干(种子含水量3.73%)贮藏(普通室温下2个月)的榆树种子萌发过程中ATP与可溶性糖含量和ATP酶、淀粉酶、抗氧化酶的活性都高于对照(种子含水量9.34%,普通室温下贮臧),说明适度的超干贮藏有利于保持种子活力.     

Environmental effects on the early stages of tassel morphogenesis in maize (Zea mays L.)

The effects of various environmental conditions on the initiation of tassel branches (NTB) and spikelet‐pairs (NSP) were examined in the stress‐sensitive maize inbred F53. Chilling induced the most important effect, with a dramatic decrease in both NTB and NSP, provided it was applied at the end of the vegetative phase and start of the floral transition phase. The primary cause of chilling‐induced abortion of the tassel branches could be oxidative stress in the leaves, since lowering light irradiance during chilling greatly reduced the effect of cold. The comparison of inbreds F53 and F2 revealed that both genotypes exhibited a similar period of cold sensitivity at the floral transition phase, although F2 was considered from field observations as a stress‐insensitive genotype (at least for tassel development). However, our results also showed a chilling acclimation response in inbred F2 but not in inbred F53. The similarities with the work by Lejeune & Bernier (1996 Plant, Cell and Environment 19, 217–224.) concerning the effect of chilling on ear initiation in the sensitive inbred, B22, are emphasized.     

Salt tolerance of maize (Zea mays L.): the role of sodium exclusion

The influence of NaCl and Na₂SO₄ on growth of two maize cultivars (Zea mays cv. Pioneer 3906 and cv. Across 8023) differing in Na⁺ uptake was investigated in two green-house experiments. Na⁺ treatment with different accompanying anions (Cl^?/SO₄^2?) showed that ion toxicity was caused by Na⁺. While shoot growth of the two cultivars was markedly affected by salt in comparison to the control during the first 2–3 weeks, there were only slight differences between the cultivars. The shoot Ca²⁺ concentration was reduced in both cultivars, and the youngest leaves contained an even lower concentration compared with the rest of the shoot. During this first phase, Across 8023 tended to have higher concentrations of Ca²⁺ than Pioneer 3906. The Na⁺-excluding cultivar Pioneer 3906 showed continuous, although reduced, growth compared with the control, while the Na⁺ concentration in the shoot decreased until flowering. Cultivar Across 8023 accumulated Na⁺ until flowering: the reduction in the growth of stressed plants was greater than that for Pioneer 3906. Leaves of cultivar Across 8023 showed clear toxic symptoms, while those of the more salt-tolerant cultivar Pioneer 3906 did not. It is concluded that Na⁺ exclusion contributes to the salt tolerance of maize.     

Effects of L-proline and post-plating temperature treatment on Maize (Zea mays L.) anther culture

Summary Comparison of different post-plating temperature regimes with a control treatment (27° C) revealed that a short-term cold (8/14°C:2/2 days or 14°C:4 days) as well as a heat treatment (30°C:14 days) increased the production of embryro-like-structures (ELS) from cultured maize anthers. The beneficial effects of short-term cold treatments were magnified 2–3 times when L-proline (PROL) was added to the induction medium (125–500 mg/L). In the best treatment (14°C:4 days, 125 mg/L L-proline) one genotype produced 143.5 ELS/100 anthers. Anthers subjected to high temperature (30°C:4 days, 30°C:7 days, 30°C:14 days) generally showed a lower response than did cold treated anthers, although genotypic differences were observed. Regeneration frequency did not appear to be affected by the presence of L-proline in the induction medium.Abbreviations ELS Embryo-like-structures - PROL L-proline     

甜玉米种子活力测定及其田间成苗能力的评估

室内和田间条件下检测18种基因型甜玉米种子活力状况的结果表明:不同甜玉米种子基因型间的活力差异显著,但均以品种京科甜116较佳.用电导率、糖含量、脱氢酶活性、醛含量、穿纸和老化发芽率均可评估田间出苗率,且前三者还可评估出苗速度,尤以电导率最佳.建立回归方程可对田间成苗能力进行预测.     

不同基因型玉米的再生能力和胚性与非胚性愈伤组织DNA的差异

研究了细胞分裂素在玉米愈伤组织诱导和植株再生中的作用,结果表明低浓度（０ ．２ ｍｇ／Ｌ） 的细胞分裂素能促进玉米幼胚诱导的愈伤组织再生,６ＢＡ 的效果比ＫＴ更好。不同品种的玉米幼胚诱导的愈伤组织的再生能力差异显著,普甜１ 号和苏玉１ 号的再生频率高达７８ ％ 和７５ ％ ,糯玉米和掖单９ 号仅为１０ ％ 和８ ％ 。植株再生途径也有所不同,普甜１ 号以器官发生为主要途径,苏玉１号则以体胚发生途径为主。经长期继代的愈伤组织失去再生能力,通过ＲＡＰＤ 方法比较发现胚性与非胚性愈伤组织的基因组之间存在差异,说明组织培养过程中愈伤组织的ＤＮＡ 发生了变异。     

Colchicine, an efficient genome-doubling agent for maize (Zea mays L.) microspores cultured in anthero

The construction of maize genotypes with high haploid induction capacity made it possible to study the effect of colchicine on maize androgenesis in vitro. Anther cultures of three hybrids were treated with 0.02% and 0.03% colchicine for 3 days at the beginning of microspore induction. Colchicine added to the induction medium had no negative influence on the androgenic responses (anther induction, induction of structures of microspore origin and their regeneration ability) of the genotypes examined. However, significantly higher fertility was observed in plants originating from colchicine-treated microspores, especially at 0.03%. Cytological examinations showed that colchicine treatment before the first microspore division efficiently arrested mitosis and resulted in homozygous doubled-haploid microspores. Under the experimental conditions, the antimitotic drug had no later effect on the division symmetry of the microspore nucleus, and unequal divisions remained dominant. Callus formation from the induced microspores seemed to be more typical (ranging between 60–70%), but embryo frequency was increased by approximately 10%, especially at the higher colchicine concentration. These results suggest that the mechanism of colchicine action in premitotic maize microspores may differ from that previously observed in wheat. Received: 15 June 1998 / Revision received: 17 September 1998 / Accepted: 3 December 1998     

RFLP mapping of quantitative trait loci controlling abscisic acid concentration in leaves of drought-stressed maize (Zea mays L.)

 Abscisic acid (ABA) concentration in leaves of drought-stressed plants is a quantitatively inherited trait. In order to identify quantitative trait loci (QTLs) controlling leaf ABA concentration (L-ABA) in maize, leaf samples were collected from 80 F_3:4 families of the cross Os420 (high L-ABA)×IABO78 (low L-ABA) tested under drought conditions in field trials conducted over 2 years. In each year, leaf samples were collected at stem elongation and near anthesis. The genetic map obtained with 106 restriction fragment length polymorphism (RFLP) loci covered 1370 cM, which represented approximately 85% of the UMC maize map. Sixteen different QTLs with a LOD>2.0 were revealed in at least one sampling. Across samplings, only four QTLs significantly influenced L-ABA, accounting for 66% of the phenotypic variation and 76% of the genetic variation among families. At these QTLs, the alleles which increased L-ABA were contributed by Os420. The two most important QTLs were mapped on chromosome 2 near csu133 and csu109a. The effects associated with the QTL near csu133 were more pronounced near anthesis. The support intervals of the four primary QTLs for L-ABA did not overlap the presumed map position of mutants impaired in ABA biosynthesis. Received: 27 January 1998 / Accepted: 22 April 1998     

Growing,physiological responses and Cd uptake of Corn (Zea mays L.) under different Cd supply

The effects of Cd on the growth and Cd uptaking in corn (Zea mays L.) were explored under different Cd stress. The results showed that no reduction in shoot and root dry matter yields were noted when the plants were grown at Cd supply levels ≤100 μmol l^?1 nutrient solution. The Cd concentration in the shoots and roots of corn increased sharply with increasing external Cd supply levels, peaked at 50 μmol l^?1, and then decreased slowly with further increasing Cd levels due to high Cd toxic effects on root growth. The concentrations of chlorophyll a, chlorophyll b and chlorophyll a + b in the leaf of corn decreased slowly with increasing external Cd supply levels. Proline concentrations of corn increased when the plants were grown under the external Cd influence. The lower concentration of Cd treatments did not influenced the growth of corn significantly, and increased the uptake of Cd, the higher levels of Cd supply caused significantly physiological resposes and decreased the Cd uptaking.     

Effect of environment on the early steps of ear initiation in maize (Zea mays L.)

The effects of environmental conditions on ear-shoot initiation have been investigated in three inbred genotypes of Zea mays L. which are used for seed production. Scanning electron microscopy (SEM) and binocular examination during the vegetative phase showed that axillary meristems are initiated at the same rate as the leaf primordia on the apical meristem, but with a delay of 5.6–7.0 plastochrons, depending on the genotype. Furthermore, the topmost axillary meristem is initiated on the same day as the tassel, whatever the genotype. One of the inbreds (B22) used in this study has been reported to exhibit, in field conditions, a reproductive failure affecting car initiation, causing the topmost car to be replaced at maturity by a sterile, leaf-like, structure. Scanning electron microscopic study of the formation of the abnormal axillary buds indicated that ear failure resulted from the early collapse of the axillary meristem followed by elongation of the prophyll or of the meristem itself. Using controlled environments, ear abortion was mimicked by a chilling treatment (10°C), given just before tassel initiation. Other factors, such as high irradiance and flooding, enhanced the abortive response. The critical stage for the main car was just before the initiation of the topmost axillary meristem which also corresponded to tassel initiation. Chilling the plants before or after tassel initiation either induced an acclimation response or had no effect. The three inbreds showed differential responses to the stress treatment, indicating that a genetic factor is implicated as well. It is suggested that chilling causes a perturbation of apical dominance which, in the responsive genotypes, represses axillary meristem development. The use of a stress-sensitive inbred such as B22 as a model system could yield some interesting clues to the mechanism of endogenous control of ear initiation in maize.