2,4—D和乙烯利对玉米幼苗抗旱性效应的研究

水分胁迫下,２０ｍｇ／Ｌ２,４－Ｄ和４００ｍｇ／Ｌ乙烯利（ＣＥＰＡ）分别不同程度地降低和提高玉米幼叶生长部位的相对含水量（ＲＷＣ）、水势（ψｗ）和渗透调节能力（ＯＡ）。胁迫后期,玉米幼叶中脯氨酸含量（Ｐｒｏ）为：ＣＥＰＡ〉对照（ＣＫｓ）〉２,４－Ｄ。随胁迫宾进行,２,４－Ｄ处理幼叶的膜相对透性（ＲＰ）始终处于较高水平且增长幅度较大,叶片延伸生长速率（ＬＥＲ）对ＲＰ的变化较为敏感;而ＣＥＰＡ处理则与     

2,4—D和乙烯利对辣椒花柄离区DNA和蛋白合成的影响

乙烯利处理后０￣４ｈ,辣椒花柄离区ＤＮＡ和蛋白质合成显著增加;２５０ｍｇ·Ｌ＾－１乙烯利处理后３２ｈ辣椒落花率达１００％,２,４－Ｄ处理的离区ＤＮＡ合成量降低,处理后０￣４ｈ促进离区蛋白质合成,４￣２４ｈ蛋白质合成量逐渐降低,１０ｍｇ·Ｌ＾－１ ２,４－Ｄ处理可抑制落花。     

渗透胁迫下2，4─D和乙烯利（CEPA）对玉米叶片延伸生长的生物物理参数的影响

２０ｍｇ／Ｌ２．４─Ｄ和４００ｍｇ／ＬＣＥＰＡ分别不同程度地促进和抑制玉米叶片的延伸生长（ＬＥＲ）,随胁迫时间延长,２,４─Ｄ处理的ＬＥＲ下降迅速,ＣＥＰＡ处理的ＬＥＲ下降缓慢。２,４─Ｄ和ＣＥＰＡ的施用分别不同程度地提高和降低了ＬＥＲ对相对含水量（ＲＷＣ）、水势、渗透势的敏感性。膨压与ＬＥＲ的相关性较小。随胁迫时间延长,干旱对照的细胞壁屈服阈值（Ｙ）呈一定下降趋势,但变化不大,２,４─Ｄ和ＣＥＰＡ处理的Ｙ值则呈一定的波动;而细胞壁的伸展性（ｍ）则明显下降,胁迫７２ｈ前,ｍ与ＬＥＲ变比规律一致,表明２,４─Ｄ和ＣＥＰＡ对生长的调控主要是通过调节ｍ来实现的。     

白Qian胚性愈伤组织长期继代培养中的分化能力及染色体稳定性 …

白Ｑｉａｎ（Ｐｉｃｅａ ｍｅｙｅｒｉ Ｒｅｈｄ．ｅｔ．Ｗｉｌｓ．）的胚性愈伤组织ＭＳ＋２,４－Ｄ１ｍｇ／Ｌ＋ＫＴ１ｍｇ／Ｌ的培养基上继代３年,增殖能力和分化潜力仍保持在原来的水平,没有明显降低的趋势。但随着继代时间的增长,胚性愈伤组织内有细胞的染色体数目发生了无规律的变化,而再生植株根尖细胞染色体数目比较稳定（２ｎ＝２８）。     

云南红豆杉愈伤组织诱导和组织培养

云南红豆杉愈伤组织的诱导频率为Ｗｈｉｔｅ〉ＭＳ〉Ｂ５,其中最高达８０％,叶片和种子之间差异不大,但不同时期的叶片差异较大,以嫩叶诱导为佳,激素配比以２,４－Ｄ２．０－３．０ｍｇ／Ｌ,ＢＡＰ０．５－１．０ｍｇ／Ｌ为宜,在继代培养阶段,Ｂ５比Ｗｈｉｔｅ和ＭＳ更适合细胞的快速生长、繁殖,并且有利于克服组织的褐化,适合于细胞生长的激素配比也以２,４－Ｄ２．０－３．０ｍｇ／Ｌ,ＢＡＰ０．５－１．０ｍｇ／Ｌｏ     

外源激素在诱导风信子花被外植体不同部位细胞再生花芽中的作用

外源激素诱导风信子（Ｈｙａｃｉｎｔｈｕｓ ｏｒｉｅｎｔａｌｉｓＬ．）同一发育时期花被外植体不同部位细胞再生花芽的实验表明∶１． 诱导花被外植体细胞再生花芽,外源激素是必需的;２． 仅有细胞分裂素就可以诱导花芽再生,生长素并不是必需的;３． 花被外植体上的不同部位的细胞再生花芽时,需要不同浓度的外源激素． 单独加６－ＢＡＰ或玉米素２ ｍ ｇ／Ｌ可以诱导花被下部的细胞再生花芽;６－ＢＡＰ或玉米素２ ｍ ｇ／Ｌ和２,４－Ｄ ０．１ ｍ ｇ／Ｌ的组合有利于花被中部的细胞再生花芽;６－ＢＡＰ或玉米素２ ｍ ｇ／Ｌ和２,４－Ｄ １．０ ｍ ｇ／Ｌ的组合能促进花被上部的细胞分化花芽     

不同因子对毛地黄叶离体培养强心苷含量的影响

对毛地黄幼叶离体培养中,影响毛地黄强心苷含量的因子进行了研究。培养基的组成成分对毛地黄强心苷的合成十分重要,ＭＳ＋２,４－Ｄ１．０ｍｇ／Ｌ＋ＢＡ１．５ｍｇ／Ｌ＋活性炭０．５％有明显促进作用;外源植物激素是合成毛地黄强心苷必需的,在ＭＳ＋２,４－Ｄ１．０ｍｇ／Ｌ基本培养基中附加ＢＡ,ＢＡ的浓度在０．２－１．５ｍｇ／Ｌ范围内,浓度越大,强心苷含量越高;不同继代培养细胞的时期对毛地黄强心苷的合成起重要作用,随着继代的增加,毛地黄强心苷的含量呈渐降趋势;细胞的生长后期对毛地黄强心苷的合成效果最佳;不同光质的光照培养对毛地黄强心苷的积累也有影响,蓝光明显提高强心苷的合成量。     

云南红豆杉细胞的悬浮培养

在云南经豆杉细胞悬浮培养中,适宜的增减基为Ｂ５,接种量为０．５－０．８ｇ干重细胞／１００ｍｌ培养基,２,４－Ｄ浓度为１．０ｍｇ／Ｌ;培养细胞的生长周期约３０ｄ;增减基中较高浓度的蔗糖（４０ｇ／Ｌ）可提高紫杉醇含量;添加的椰子汁（ＣＭ）、酪蛋白氨基酸（ＣＡ）和水解乳蛋白（ＬＨ）３种有机添加剂均能提高培养细胞中紫杉醇的含量,但只有ＣＭ和ＣＡ能促进细胞的生长。于Ｂ５培养基中添国不同浓度的ＮＨ４ＮＯ３对培     

影响木薯次生胚状体发生及植株再生因素的研究

研究了在外植体的不同发育阶段中,碳源以及不同的生长激素配比对木薯次生胚状体诱导及植株再生的影响。结果表明：以固体成熟培养基上生长１５ｄ的胚状体子叶为外植体,次生胚状体的产量最高,达２９．３个成熟胚状体／１个外植体。在次生胚状体的诱导阶段,以麦芽糖（４０ｇ／Ｌ）代替蔗糖作碳源,能同时提高次生胚状体的产量（３２．５个胚次体／１个外植体）及植株再生频率（７４．３％）。２,４－Ｄ与ＰＰ３３３;（０．１ｍｇ／Ｌ）配合能提高植株再生频率到７７．６％。２,４－Ｄ与ＢＡＰ（２ｍｇ／Ｌ）或激动素（２．０ｍｇ／Ｌ）配合则大大降低了胚状体诱导及植株再生频率。     

2，4_D对甘薯体细胞胚胎发生的调控

将来源于‘徐薯１８’叶片的胚性愈伤组织,接种在含有不同２,４Ｄ浓度的液体ＭＳ培养基中进行悬浮培养,悬浮细胞表现出不同的形态结构、分裂方式和发育途径：２,４Ｄ浓度为１ｍｇ／Ｌ时,细胞均等分裂,增殖迅速;不含２,４Ｄ时,细胞多进行不均等分裂,并发育成体细胞胚。不同２,４Ｄ浓度中培养的悬浮细胞,其胞外过氧化物同工酶谱及其随时间变化的方式有很大差异,并与细胞的生长、发育过程密切相关     

Cortical Actin Filaments Potentially Interact with Cortical Microtubules in Regulating Polarity of Cell Expansion in Primary Roots of Maize (Zea mays L.)

Evidence is accumulating implicating cortical microtubules in the directional control of cell expansion. However, the role of actin filaments in this process is still uncertain. To determine the involvement of actin in cell elongation, the organization of actin filaments in primary roots of maize (Zea mays L.) was examined by use of an improved fluorochrome-conjugated phalloidin-labeling method. With this method, a previously undetected state of actin organization was revealed in the elongation and maturation zone of maize roots. Fine transversely oriented cortical actin was observed in all cells of the elongation zone, including the epidermis, cortex, and vascular tissues. The orientation of cortical actin shifted from a predominantly transverse orientation to oblique, longitudinal, and/or random arrangements as the cells matured. The reorientation of cortical actin in maturing root cells mimics the behavior of cortical microtubules reported in other studies. Furthermore, roots treated with the microtubule-stabilizing drug taxol improved the quality of actin preservation as evidenced by the thicker bundles of cortical actin. This suggested that taxol was also capable of stabilizing the cortical actin networks. The elongation of roots exposed to 1 micromole Latrunculin B, an actin-disrupting drug, was inhibited, and after 24 h the roots exhibited moderate swelling particularly along the elongation zone. Latrunculin B also caused microtubules to reorient from transverse to oblique arrays. The results from this study provide evidence that cortical microtubules and actin filaments respond in a coordinated way to environmental signals and may well depend on both elements of the cytoskeleton.     

Microtubules spatial alterations in root cells of Brassica rapa under clinorotation

Organization of tubulin cytoskeleton in epidermis and cortex cells in different root growth zones in Brassica rapa L. 6-day-old seedlings under clinorotation has been investigated. It was shown that changes in cortical microtubules orientation occur only in the distal elongation zone. In control, cortical microtubule arrays oriented transversely to the root long axis. Whereas under clinorotation an appearance of shorter randomly organized cortical microtubules was observed. Simultaneously, a significant decrease in a cell length in the central elongation zone under clinorotation was revealed. It is suggested that the decline of anisotropic growth, typical for central elongation zone cells, is connected with cortical microtubules disorientation under clinorotation.     

Microtubules in epidermal and cortical root cells of Brassica rapa during clinorotation

Using confocal microscopy the organization of tubulin cytoskeleton including endoplasmic and cortical microtubules (CMTs) has been studied in epidermal and cortical cells of the different growth zones of main root of Brassica rapa L. 6-days-old seedlings in control conditions and under clinorotation. It was shown that changes in CMTs orientation occured only in the distal elongation zone (DEZ). In the control, CMT arrays oriented transversely to the root long axis. Under clinorotation appearance of the shorter randomly organized CMTs was observed. Simultaneously, a significant decrease in the cell length in the central elongation zone (CEZ) under clinorotation was detected. It is suggested that the decline of anisotropic growth typical for CEZ cells is connected with CMTs disorientation under clinorotation.     

Internodal elongation and orientation of cellulose microfibrils and microtubules in deepwater rice

Excised stem sections of deepwater rice (Oryza sativa L.) containing the highest internode were used to study the induction of rapid internodal elongation by gibberellin (GA). It has been shown before that this growth response is based on enhanced cell division in the intercalary meristem and on increased cell elongation. In both GA-treated and control stem sections, the basal 5-mm region of the highest internode grows at the fastest rate. During 24 h of GA treatment, the internodal elongation zone expands from 15 to 35 mm. Gibberellin does not promote elongation of internodes from which the intercalary meristem has been excised. The orientation of cellulose microfibrils (CMFs) is a determining factor in cell growth. Elongation is favored when CMFs are oriented transversely to the direction of growth while elongation is limited when CMFs are oriented in the oblique or longitudinal direction. The orientation of CMFs in parenchymal cells of GA-treated and control internodes is transverse throughout the internode, indicating that CMFs do not restrict elongation of these cells. Changes in CMF orientation were observed in epidermal cells, however. In the basal 5-mm zone of the internode, which includes the intercalary meristem, CMFs of the epidermal cell walls are transversely oriented in both GA-treated and control stem sections. In slowly growing control internodes, CMF orientation changes to the oblique as cells are displaced from this basal 5-mm zone to the region above it. In GA-treated rapidly growing internodes, the reorientation of CMFs from the transverse to the oblique is more gradual and extends over the 35-mm length of the elongation zone. The CMFs of older epidermal cells are obliquely oriented in control and GA-treated internodes. The orientation of the CMFs parallels that of the cortical microtubules. This is consistent with the hypothesis that cortical microtubules determine the direction of CMF deposition. We conclude that GA acts on cells that have transversely oriented CMFs but does not promote growth of cells whose CMFs are already obliquely oriented at the start of GA treatment.     

Gravity-induced changes in intracellular potentials in elongating cortical cells of mung bean roots

Gravity-induced changes in intracellular potentials in primary roots of 2-day-old mung bean (Vigna mungo L. cv. black matpe) seedlings were investigated using glass microelectrodes held by 3-dimensional hydraulic micro-drives. The electrodes were inserted into outer cortical cells within the elongation zone. Intracellular potentials, angle of root orientation with respect to gravity, and position within the root of the impaled cortical cell were measured simultaneously. Gravistimulation caused intracellular potential changes in cortical cells of the elongation zone. When the roots were oriented vertically, the intracellular potentials of the outer cortical cells (2 mm behind the root apex) were approximately - 115 mV. When the roots were placed horizontally cortical cells on the upper side hyperpolarized to - 154 mV within 30 s while cortical cells on the lower side depolarized to about - 62 mV. This electrical asymmetry did not occur in cells of the maturation zone. Because attempts to insert the electrode into cells of the root cap were unsuccessful, these cells were not measured. The hyperpolarization of cortical cells on the upper side was greatly reduced upon application of N,N'-dicyclohexylcarbodiimide (DCCD), an inhibitor of respiratory energy coupling. When stimulated roots were returned to the vertical, the degree of hyperpolarization of cortical cells on the previous upper side decreased within 30 s and approached that of cortical cells in non-stimulated roots. This cycle of hyperpolarization/loss of hyperpolarization was repeatable at least ten times by alternately turning the root from the vertical to the horizontal and back again. The very short (<30 s) lag period of these electrical changes indicates that they may result from stimulus-perception and transduction within the elongation zone rather than from transmission of a signal from the root cap.     

Relationship between microtubule orientation and patterns of cell expansion in developing cortical cells of Lemna minor roots

In actively growing cortical cells in the elongation zone of Lemna minor L. roots, both longitudinal (radial and tangential) and transverse walls expand in both length and width. The longitudinal walls of the three types of cortical cells in the root (i.e. outer, middle and inner) showed the largest expansion in the longitudinal axis. In contrast, the inner cortical cells exhibited the least expansion in width, whereas the middle cortical cells displayed the largest expansion in width. Thus, the profiles of the expansion of longitudinal walls were characteristic for the three types of cortical cells. In this study, both the orientation of cortical microtubule (MT) arrays and their dynamic reorientation, and the density of cortical MTs, were documented and correlated to the patterns of cell wall expansion. Significantly, transverse arrays of cortical MTs were most prominent in the radial walls of the inner cortical cells, and least so in those of the middle cortical cells. Toward the base of roots, beyond the elongation zone, the orientation of cortical MTs shifted continuously from transverse to oblique and then to longitudinal. In this case, the rate of shift in the orientation of cortical MTs along the root axis was appreciably faster in the middle cortical cells than in the other two types of cortical cells. Interestingly, the continuous change in cortical MT orientation was not confirmed in the transverse walls which showed much smaller two-dimensional expansion than the radial walls. Additionally, the presence of fragmented or shortened cortical MTs rapidly increased concomitantly with the decrease of transversely oriented cortical MTs. This relationship was especially prominent in the transverse walls of the inner cortical cells, which displayed the least expansion among the three types of cortical cells investigated. In the root elongation zone, the density of cortical MTs in the inner cortical cells was about three times higher than that in the other two cortical cell types. These results indicate that in the early stage of cell expansion, the orientation of cortical MTs determines a preferential direction of cell expansion and both the shifting orientation and density of cortical MTs affect the magnitude of expansion in width of the cell wall.     

Auxin, actin and growth of the Arabidopsis thaliana primary root

To understand how auxin regulates root growth, we quantified cell division and elemental elongation, and examined actin organization in the primary root of Arabidopsis thaliana. In treatments for 48 h that inhibited root elongation rate by 50%, we find that auxins and auxin-transport inhibitors can be divided into two classes based on their effects on cell division, elongation and actin organization. Indole acetic acid (IAA), 1-naphthalene acetic acid (NAA) and tri-iodobenzoic acid (TIBA) inhibit root growth primarily through reducing the length of the growth zone rather than the maximal rate of elemental elongation and they do not reduce cell production rate. These three compounds have little effect on the extent of filamentous actin, as imaged in living cells or by chemical fixation and immuno-cytochemistry, but tend to increase actin bundling. In contrast, 2,4-dichlorophenoxy-acetic acid (2,4-D) and naphthylphthalamic acid (NPA) inhibit root growth primarily by reducing cell production rate. These compounds remove actin and slow down cytoplasmic streaming, but do not lead to mislocalization of the auxin-efflux proteins, PIN1 or PIN2. The effects of 2,4-D and NPA were mimicked by the actin inhibitor, latrunculin B. The effects of these compounds on actin were also elicited by a 2 h treatment at higher concentration but were not seen in two mutants, eir1-1 and aux1-7, with deficient auxin transport. Our results show that IAA regulates the size of the root elongation zone whereas 2,4-D affects cell production and actin-dependent processes; and, further, that elemental elongation and localization of PINs are appreciably independent of actin.     

Root growth, developmental changes in the apex, and hydraulic conductivity for Opuntia ficus-indica during drought

Developmental changes in the root apex and accompanying changes in lateral root growth and root hydraulic conductivity were examined for Opuntia ficus-indica (L.) Miller during rapid drying, as occurs for roots near the soil surface, and more gradual drying, as occurs in deeper soil layers. During 7 d of rapid drying (in containers with a 3-cm depth of vermiculite), the rate of root growth decreased sharply and most root apices died; such a determinate pattern of root growth was not due to meristem exhaustion but rather to meristem mortality after 3 d of drying. The length of the meristem, the duration of the cell division cycle, and the length of the elongation zone were unchanged during rapid drying. During 14 d of gradual drying (in containers with a 6-cm depth of vermiculite), root mortality was relatively low; the length of the elongation zone decreased by 70%, the number of meristematic cells decreased 30%, and the duration of the cell cycle increased by 36%. Root hydraulic conductivity ( L _P) decreased to one half during both drying treatments; L _P was restored by 2 d of rewetting owing to the emergence of lateral roots following rapid drying and to renewed apical elongation following gradual drying. Thus, in response to drought, the apical meristems of roots of O. ficus-indica near the surface die, whereas deeper in the substrate cell division and elongation in root apices continue. Water uptake in response to rainfall in the field can be enhanced by lateral root proliferation near the soil surface and additionally by resumption of apical growth for deeper roots.     

Halogenated Auxins Affect Microtubules and Root Elongation in Lactuca sativa

We studied the effect of 4,4,4-trifluoro-3-(indole-3-)butyric acid (TFIBA), a recently described root growth stimulator, and 5,6-dichloro-indole-3-acetic acid (DCIAA) on growth and microtubule (MT) organization in roots of Lactuca sativa L. DCIAA and indole-3-butyric acid (IBA) inhibited root elongation and depolymerized MTs in the cortex of the elongation zone, inhibited the elongation of stele cells, and promoted xylem maturation. Both auxins caused the plane of cell division to shift from anticlinal to periclinal. In contrast, TFIBA (100 micromolar) promoted elongation of primary roots by 40% and stimulated the elongation of lateral roots, even in the presence of IBA, the microtubular inhibitors oryzalin and taxol, or the auxin transport inhibitor naphthylphthalamic acid. However, TFIBA inhibited the formation of lateral root primordia. Immunostaining showed that TFIBA stabilized MTs orientation perpendicular to the root axis, doubled the cortical cell length, but delayed xylem maturation. The data indicate that the auxin-induced inhibition of elongation and swelling of roots results from reoriented phragmoplasts, the destabilization of MTs in elongating cells, and promotion of vessel formation. In contrast, TFIBA induced promotion of root elongation by enhancing cell length, prolonging transverse MT orientation, delaying cell and xylem maturation.     

Stunted plant 1 mediates effects of cytokinin, but not of auxin, on cell division and expansion in the root of Arabidopsis

Plants control organ growth rate by adjusting the rate and duration of cell division and expansion. Surprisingly, there have been few studies where both parameters have been measured in the same material, and thus we have little understanding of how division and expansion are regulated interdependently. We have investigated this regulation in the root meristem of the stunted plant 1 (stp1) mutation of Arabidopsis, the roots of which elongate more slowly than those of the wild type and fail to accelerate. We used a kinematic method to quantify the spatial distribution of the rate and extent of cell division and expansion, and we compared stp1 with wild type and with wild type treated with exogenous cytokinin (1 microM zeatin) or auxin (30 nM 2,4-dichlorophenoxyacetic acid). All treatments reduced average cell division rates, which reduced cell production by the meristem. Auxin lowered root elongation by narrowing the elongation zone and reducing the time spent by a cell in this zone, but did not decrease maximal strain rate. In addition, auxin increased the length of the meristem. In contrast, cytokinin reduced root elongation by lowering maximal strain rate, but did not change the time spent by a cell within the elongation zone; also, cytokinin blocked the increase in length and cell number of the meristem and elongation zone. The cytokinin-treated wild type phenocopied stp1 in nearly every detail, supporting the hypothesis that cytokinin affects root growth via STP1. The opposite effects of auxin and cytokinin suggest that the balance of these hormones may control the size of the meristem.