Ethylene production in habituated and auxin-requiring tobacco callus cultures. Does ethylene play a role in the habituation?

Ethylene production of habituated and auxin-requiring tobacco ( Nicotiana tabacum L. cv. Xanthi) callus cultures were compared. More ethylene was produced by auxinrequiring i.e. auxin-heterotrophic cultures than by habituated ones. Treatment with 2,4-dichlorophenoxyacetic acid increased the ethylene evolution of habituated cultures over the range 10⁻⁷ to 10⁻⁴ M , which suggests that the higher ethylene production of auxin-dependent callus is caused by the 2,4-D in the medium. The IAA levels depended on the age of both types of callus cultures.     

6-甲氧基-2-并噁唑啉酮的一些生理作用

已有研究证实,６－甲氧基－２－并噁唑啉酮（６－ｍｅｔｈｏｘｙ－２－ｂｅｎｚｏｘａｚｏｌｉｎｏｎｅ,ＭＢＯＡ）是引起玉米胚芽鞘向光性运动的主要物质。本文采用生物测定和ＨＰＬＣ分析等方法,对ＭＢＯＡ的生理作用特点做进一步的探讨,结果表明：１．光刺激下收集的胚芽鞘分泌物主要成份是ＭＢＯＡ,该物质明显抑制鸡冠花和水芹下胚轴的伸长。２．将ＭＢＯＡ与ＩＡＡ混合处理胚芽鞘,产生相互拮抗的效果。３．单侧放置含ＭＢＯＡ琼脂块能引起去顶胚芽鞘弯曲生长。４．伤害胁迫使胚芽鞘ＭＢＯＡ含量增加。因此,ＭＢＯＡ不仅是引起植物向光性运动的物质,也是与抗伤害胁迫有关的天然抑制物质,其生理功能之一是与生长素的作用相互拮抗,并抑制植物生长。     

生长素和赤霉素对离体水仙花茎切段伸长的影响

以离体水仙(Narcissustazettavar.chinensis)花茎切段为材料,通过外源吲哚-3-乙酸(Indole-3-aceticacid,IAA)和赤霉素A3(GA3)处理,结合内源激素分析,研究了这两种激素对水仙花茎切段伸长的影响,以及它们之间的相互作用。结果表明:外源50μmol/LIAA和30μmol/LGA3均能促进花茎切段的伸长,其中IAA的促进作用大于GA3。200μmol/L生长素运输抑制剂2,3,5-三碘苯甲酸(2,3,5-Triiodobenzoicacid,TIBA)和65μmol/L赤霉素合成抑制剂烯效唑(Uniconazole,S-3307)均显著抑制花茎切段的伸长。外源50μmol/LIAA处理明显增加内源GA1 3的含量,是对照的3.40倍;外源30μmol/LGA3处理对内源IAA含量影响不明显,说明IAA对维持花茎切段内源活性GA水平起重要作用,IAA和活性GA共同发挥调控花茎切段伸长的作用。     

Temporal Morphology and Cap Formation in Acetabularia-Ii. Effects of Morphactin and Auxin

Afin d'apporter des arguments supplémentaires à?hypothese selon laquelle les rhythms circadiens sont impliqués dans la morphogénèse, des expériences ont été réalisées de manière a mettre en évidence la relation éventuelle de dépendance entre le moment (dans le cycle de 24 heures) où commence le traitement et ? effet (1) de la morphactine, un inhibiteur compétitif de ?'auxine et (2) de ? auxine (IAA).

Les résultats ont montré que (1) ? effet inhibiteur de la morphactine varie considérablement selon le moment auquel le traitement a commencé, plusieurs semaines avant ? expression morphogénétique; (2) le maximum d'inhibition change avec le stade de développement et le degré d'inhibition diminue avec le temps; (3) ?'IAA accélerè la formation du chapeau lorsque le traitement a commencé pendant la phase de croissance rapide des algues; ? effet depend du moment (du cycle de 24 heures) auquel il a commencé son effet diminue au cours du temps; (4) lorsque le traitement a commencé avec des algues plus petites que les precédéntes, il exerce un effet transitoirement inhibiteur qui dépend du moment du cycle de 24 heures auquel il a commence; (5) les fragments anucléés aussi répondent différentiellement à un traitement à ? IAA commencé a différents moments du cycle de 24 heures; ? effet est plus net quand des mRNA ont été accumulés; (6) ? effet de ? IAA n'est pas cumulé a celui d'une perturbation du cycle L-D; celui de la morphactine n'est pas modifyé ou est légérement amélioré par une perturbation du cycle L-D.

Mots clefs–Acetabularia, rhymes circadiens, morphogénèse, auxine, morphactine.

In order to support the hypothesis that circadian rhythms are implicated in cap formation, experiments were undertaken on the possible time-dependency of the effects of (a) a competitive inhibitor of auxins, morphactin and (b) of auxin (IAA). It was found that: (i) the inhibitory effect of morphactin varies dramatically with the time at which the several weeks' treatment was first begun; (ii) the maximum inhibition varies with development and decreases with time; (iii) IAA accelerates cap formation when the algae are submitted to IAA during the exponential growth phase; the effect is time dependent and decreases with time; (iv) IAA first applied on smaller algae has a transient inhibitory effect which is time dependent; (v) anucleate fragments also respond differentially to an IAA treatment begun at several times in the 24-hr cycle, most clearly when newly formed mRNA have been accumulated and (vi) the effect of iAA is not cumulative with that of a LD shift; that of morphactin is not, or only slightly, improved by a LD shift.     

Changes in IAA, tryptophan and activity of soluble peroxidase associated with zygotic embryogenesis in Araucaria angustifolia (Brazilian pine)

In A. angustifolia seeds the highest values of freeIAA occurred in the embryonic axis, at the initial phases of development. Thesevalues decreased sharply coincident with the increase of IAA with thedifferentiation of cotyledons and seed elongation. During seed development,tryptophan concentrations varied inversely with free IAA and directly withconjugated IAA. An increase in peroxidase activity was followed by a decreaseinfree IAA in the embryo axis, and in conjugated IAA in the megagametophyte.Megagametophyte tissues did not exhibit significant variation in free IAAduringseed development. Following the stage where cotyledons arise, tryptophandecreased in the megagametophyte and increased in the cotyledons and embryonicaxis.