生长素极必运输的自动抑制

以豌豆（Ｐｉｓｕｍ ｓａｔｉｖｕｍ Ｌ．）和绿豆（Ｐｈａｓｅｏｌｕｓ ｒａｄｉａｔｕｓ Ｌ．）为材料证明了ＩＡＡ极性运输的自动抑制现象。用改进的“供体－受体技术”证明：受体中的ＩＡＡ可抑制＾３Ｈ－ＩＡＡ的极性运输,抑制程度随受体中加入ＩＡＡ浓度的增加而增加;在“Ｙ”型外植体一侧切口施用的ＩＡＡ也可抑制＾３ＨＩＡＡ在另一侧的极性运输,并导致＾３Ｈ－ＩＡＡ在该侧组织中的积累以及代谢或钝化的增加。此外,     

生长素极性运输抑制剂(TIBA)对烟草离体花柄花芽分化的影响

在只含6-BA(2mg/L)的MS培养基上,烟草花柄外植体形态学基端膨大,上着生再生花芽,而花柄中部大多都形成愈伤组织。添加IAA(2,10,20 mg/L)后,花柄基端膨大的现象依然存在,但再生花芽的分布并不限于基端,在花柄中部、顶端都可见再生花芽。花柄外植体中部愈伤组织的形成也随添加的IAA和IAA浓度升高而受到抑制。在上述培养基中添加生长素极性运输抑制剂TIBA后,无一花柄中部能形成愈伤组织,再生花芽的形态变化也很大,有具锥形花柄的花芽、喇叭叶和一些难于确定由何种器官衍生而来的喇叭状器官。这些异于正常形态的器官发生,显然与花柄外植体中生长素极性运输受抑制有关,本文对它们的形成机理作了一些推测。     

隐花素在生长素调控拟南芥下胚轴伸长中的作用分析

以拟南芥野生型(Col-4)和隐花素双突变体cry1cry2为材料,研究不同光照条件下不同浓度吲哚乙酸(IAA)和IAA极性运输抑制剂氨基酞氨酸(NPA)对幼苗下胚轴伸长的影响。结果显示,低浓度IAA(10-7mol/L)可促进连续白光和红光下cry1cry2幼苗下胚轴伸长,而连续蓝光下cry1cry2下胚轴的伸长则受到抑制。蓝光下相同浓度的NPA对cry1cry2幼苗下胚轴伸长的抑制程度比野生型要小。RT-PCR分析结果显示,瞬时蓝光处理时IAA合成关键酶基因IGPS以及生长素应答基因IAA1和IAA5在cry1cry2突变体中的转录水平比野生型中要高。这表明隐花素可能部分通过调节IAA合成和/或IAA极性运输,介导蓝光调控拟南芥下胚轴的伸长。     

吲哚乙酸、吲哚乙酸氧化酶和几种愈伤组织生长的关系

将大豆(Glycine max(L.)Merr.)哈密瓜(Cucumus melo L.var saccharinus)烟草(Nicotianatabacum L.)和毛白杨(Populus tometasa Carr.)的愈伤组织分别接种在附加IAA4毫克/升和激动素0.5毫克/升的Miller液体培养基上。烟草和哈密瓜的愈伤组织迅速地生长,能持续到50天左右;而大豆和毛白杨的愈伤组织生长缓慢,且20天就停止生长。 测定培养中IAA的消耗情况表明,接种大豆和哈密瓜的愈伤组织的培养液IAA消耗最快,到第四天就消耗完了;接种毛白杨愈伤组织的培养液IAA消耗次之,到第六天也消耗完了;接种烟草愈伤组织的培养液IAA消耗最慢,到第20天仍有加入量的2.8％。 培养液中IAA的消耗与吲哚乙酸氧化酶的活性有密切的关系。吲哚乙酸氧化酶的活性越高,IAA消耗越快,大豆、烟草和毛白杨愈伤组织的生长也随IAA的降低而减慢,但是哈密瓜愈伤组织的生长在IAA消耗完以后,仍能持续生长多日。因此可以认为有些愈伤组织的生长为其所包含的吲哚乙酸氧化酶的活性所制约;有的并不如此。     

几种抑制剂对钾和IAA诱导的离体黄瓜子叶不定根形成的影响

应用离体黄瓜(Cucumis sativus L.)子叶生根试法测定了几种抑制剂对钾和IAA诱导生根的影响。实验结果表明:7×10~(-4)～7×10~(-1)mmol/L的5-氟尿嘧啶和3.5×10~(-4)～1.05×10~(-2)mmoL/L的环已亚胺明显抑制钾和IAA诱导的离体黄瓜子叶的生根;0.1～1.0mmol/L的钒酸钠显著抑制钾和IAA诱导的离体黄瓜子叶的生根;2×10~(-4)～2×10~(-1)mmol/L的2,3,5-三碘苯甲酸也明显抑制钾和IAA诱导的离体黄瓜子叶的生根。钾诱导的生根与IAA诱导的生根密切相关,有可能钾对生根的促进作用是通过影响内源IAA的水平而实现的。     

氚标记吲哚-3-乙酸的制备(简报)

本文用同位素交换法制得氚标记吲哚一3-乙酸(~3H-IAA)。制备方法是:向带有小匙(置有5.6mg IAA)的玻璃     

硼对吲哚乙酸在植物体内运输的影响

以绿豆为指示作物,研究缺硼对侧芽生长及³H-吲哚乙酸（IAA）在完整植株体内运输的影响.结果表明：缺硼诱导侧芽生长,导致³H-IAA移动峰靠近植株顶端,茎中³H-IAA的放射性活度也低于供硼充分的植株,说明缺硼抑制了³H-IAA在植株体内的极性运输;无论缺硼与否侧芽中均未检测到³H-IAA,所以侧芽的生长与³H-IAA在其中的积累没有关系,表明硼并不是通过调节IAA在侧芽中的积累,而是通过调节IAA在主茎的移动流调控侧芽生长;给缺硼植株供硼24 h能够恢复IAA在植株体内的极性运输能力.     

色氨酸促进烟草离体花柄翘尾的效应(简报)

L型和D型色氨酸均能促使离体烟草花柄翘尾，即花柄生理性基部向培养基上方弯曲，翘尾率达100％。不同浓度的IAA均不出现色氨酸引起的高翘尾率。生长素极性运输抑制剂（TIBA）有效地抑制花柄表面愈伤组织的形成，但不提高IAA引起的花柄翘尾的百分率。     

烟草茎薄层培养直接形成花芽及其极性现象(简报)

烟草的表皮薄层组织离体培养在IAA和KT的适当浓度下能直接形成花芽原基或营养芽原基。形成花原基的潜在能力,在花梗区到茎基部有明显的生理梯度。花原基细胞核的DNA含量高于营养芽及愈伤细胞。培养基中IAA和KT浓度相等(10~(-6)mol/L)时,花芽原基发生在外植体的形态学下端,有极性表现。KT浓度提高(10~(-5)mol/L)则两端均发生营养芽原基;KT浓度降低(10~(-7)或5×10~(-7)mol/L)则两端发生愈伤组织,极性消失。     

烯效唑对水稻幼苗内源IAA含量的影响

研究了烯效唑对3~H-IAA色氨酸合成3~H-IAA的效率及对IAA氧化酶活性的影响,以探讨烯效唑延缓植物生长的作用机理。结果表明,烯效唑对水稻(Oryza sativa L.)幼苗生长的控制效应与其降低内源IAA含量有关,烯效唑浸种处理降低水稻幼苗内源IAA含量有两条途径,其一是提高水稻幼苗IAA氧化酶活性,增强内源IAA的氧化;其二是阻抑内源IAA的合成。烯效唑除阻抑内源赤霉素的生物合成而延缓作物生长外,通过降低内源IAA水平也可能是其延缓作物生长的一个原因。     

Autoinhibition in Polar Transport of Indoleacetic Acid

Autoinhibition in polar transport of 3H-IAA from donor to receiver was demonstrated in pea ( Pisum sativum L. ) and mung bean ( Phaseolus radiatus L. ) using either classic "donor-receiver system" where unlabelled IAA was present in the receiver or using "Y" form explants where tmlabelled IAA in lanolin was applied to the cut surface of a separate side of the explants. Application of unlabelled IAA resulted in accmnulation and high rate of metabolism of SH-IAA in the labelled tissues, and these were further stimulated by prolonging the experimental period.     

Autoinhibition of indoleacetic acid transport in the shoots of two-branched pea (Pisum sativum) plants and its relationship to correlative dominance

Two-branched pea plants ( Pisum sativum L. cv. Lisa ZS) with different dominance degrees, obtained by removing the epicotyl shortly after germination, were used to study the interaction between the polar transport of indoleacetic acid (IAA) in both branches of the plants and its relationship to correlative dominance. The dominant shoot had higher transport capacity for 3H-IAA, exported more IAA out of its apex and possessed more endogenous IAA in apex and the first internode than the dominated one. Decapitation of the dominant shoot resulted in a rapid resumption of growth in the dominated shoot, accompanied by a considerable increase in its capacity to export endogenous IAA and to transport 3H-IAA. Parallel experiments with intact two-branched plants and Y-formed explants showed that the 3H-IAA transport on one side was inhibited by the other branch apex or by pre-application of 12C-IAA to the cut stump of the decapitated side. The higher the concentration of 12C-IAA applied to the cut stump of one side of the Y-form explant was used, the stronger the 3H-IAA transport was inhibited and the more the transported IAA was conjugated above the junction on the other side. The results of these experiments support the autoinhibition hypothesis at junctions. The relationship between elongation growth and IAA export/transport in the two-branch pea plants is considered.     

Plant regeneration via organogenesis in marigold

Regeneration of whole plants of marigold (Tagetes erecta L.) was achieved by organogenesis using leaf explants. Leaf segments about 0.25 cm² were taken from 3-week-old in vitro plantlets and cultured on MS basal medium containing BA with different auxins (NAA, 2,4-D and IAA). The exposure time of the explants on the regeneration medium was tested. The highest values for regeneration were obtained with BA (13.3 M) and IAA (17.1 M). Thirteen days was the best time of exposure of the explant to the regeneration medium for shoot induction.     

High-affinity auxin transport by the AUX1 influx carrier protein

In plants, auxin is a key regulator of development and is unique among plant hormones in that its function requires polarized transport between neighboring cells to form concentration gradients across various plant tissues. Although putative auxin-influx and -efflux transporters have been identified by using molecular genetic approaches, a detailed functional understanding for many of these transporters remains undetermined. Here we present the functional characterization of the auxin-influx carrier AUX1. Upon expression of AUX1 in Xenopus oocytes, saturable, pH-dependent uptake of 3H-IAA was measured. Mutations in AUX1 that abrogate physiological responses to IAA in planta resulted in loss or reduction of 3H-IAA uptake in AUX1-expressing oocytes. AUX1-mediated uptake of 3H-IAA was reduced by the IAA analogs 2,4-D and 1-NOA, but not by other auxin analogs. The measured Km for AUX1-mediated uptake of 3H-IAA was at concentrations at which physiological responses are observed for exogenously added IAA and 2,4-D. This is the first report demonstrating detailed functional characteristics of a plant auxin-influx transporter. This biochemical characterization provides new insights and a novel tool for studying auxin entry into cells and its pivotal roles in plant growth and development.     

Patterns of auxin and abscisic acid movement in the tips of gravistimulated primary roots of maize

Because both abscisic acid (ABA) and auxin (IAA) have been suggested as possible chemical mediators of differential growth during root gravitropism, we compared with redistribution of label from applied ³H-IAA and ³H-ABA during maize root gravitropism and examined the relative basipetal movement of ³H-IAA and ³H-ABA applied to the caps of vertical roots. Lateral movement of ³H-ABA across the tips of vertical roots was non-polar and about 2-fold greater than lateral movement of ³H-IAA (also non-polar). The greater movement of ABA was not due to enhanced uptake since the uptake of ³H-IAA was greater than that of ³H-ABA. Basipetal movement of label from ³H-IAA or ³H-ABA applied to the root cap was determined by measuring radioactivity in successive 1 mm sections behind the tip 90 minutes after application. ABA remained largely in the first mm (point of application) whereas IAA was concentrated in the region 2–4 mm from the tip with substantial levels found 7–8 mm from the tip. Pretreatment with inhibitors of polar auxin transport decreased both gravicurvature and the basipetal movement of IAA. When roots were placed horizontally, the movement of ³H-IAA from top to bottom across the cap was enhanced relative to movement from bottom to top whereas the pattern of movement of label from ³H-ABA was unaffected. These results are consistent with the hypothesis that IAA plays a role in root gravitropism but contrary to the idea that gravi-induced asymmetric distribution of ABA contributes to the response.     

Endogenous levels of abscisic acid and indole-3-acetic acid during in vitro rooting of Wild Cherry explants produced by micropropagation

Levels of endogenous ABA and IAA were quantified during the first week of in vitro rooting of Wild Cherry (Prunus avium L.) using IBA in the culture medium. Hormones were measured in the apical, median and basal parts of the explants using an avidin-biotin based enzyme linked immunosorbent assay (ELISA), after a purification of the methanolic extracts by high-performance liquid chromatography (HPLC).Root primordia started to differentiate from day 5 at the basal part of the explants. ABA and IAA showed considerable changes and high levels were detected during the first week of culture. ABA levels increased transiently mainly in the apical part during root formation. Exogenous IBA was possibly transformed into IAA mainly in the basal part of the explants.     

Polar Transport of Indole-3-Acetic Acid in Relation to Rooting in Carnation Cuttings: Influence of Cold Storage Duration and Cultivar

The influence of cold storage of cuttings on the transport and metabolism of indole-3-acetic acid (IAA) and the rooting were studied in two carnation (Dianthus caryophyllus L.) cultivars (Oriana and Elsy), which are known to exhibit very distinct rooting characteristics. The percentage of rooting at 11 d after planting increased with the storage period particularly in Oriana, but the values in Elsy were higher than in Oriana. Auxin transport was measured by applying ³H-IAA to stem sections. Irrespective of the section localization, the oldest node (node) or the basal internode (base), the transport increased as the storage period increased from 2 to 12 weeks in Oriana and from 2 to 8 weeks in Elsy cuttings. The auxin transport rate was higher in bases than in nodes and also in Elsy than in Oriana at a given storage period. IAA oxidation and hydrolyzation of IAA conjugates (determined by extracting the sections with acetonitrile and NaOH once the basipetal IAA movement ceased after a 24 h transport period) showed a negative, highly significant correlation with the amount of IAA transported. Although the rooting percentage and IAA transport were higher in Elsy than in Oriana, the differences in rooting between the cultivars could not be explained solely by differences in IAA transport.     

Asymmetric distribution of auxin correlates with gravitropism and phototropism but not with autostraightening (autotropism) in pea epicotyls

The relationships between the distribution of the native auxin indole-3-acetic acid (IAA) and tropisms in the epicotyl of red light-grown pea (Pisum sativum L.) seedlings have been investigated. The distribution measurement was made in a defined zone of the third internode, using (3)H-IAA applied from the plumule as a tracer. The tropisms investigated were gravitropism, pulse-induced phototropism, and time-dependent phototropism. The investigation was extended to the phase of autostraightening (autotropism) that followed gravitropic curvature. It was found that IAA is asymmetrically distributed between the two halves of the zone, with a greater IAA level occurring on the convex side, at early stages of gravitropic and phototropic curvatures. This asymmetry was found in epidermal peels and, except for one case (pulse-induced phototropism), no asymmetry was detected in whole tissues. It was concluded, in support of earlier results, that auxin asymmetry mediates gravitropism and phototropism and that the epidermis or peripheral cell layers play an important role in the establishment of auxin asymmetry in pea epicotyls. During autostraightening, which results from a reversal of growth asymmetry, the extent of IAA asymmetry was reduced, but its direction was not reversed. This result demonstrated that autostraightening is not regulated through auxin distribution. In this study, the growth on either side of the investigated zone was also measured. In some cases, the measured IAA distribution could not adequately explain the local growth rate, necessitating further detailed investigation.