Eklund L, Little C H
Department of Engineering and Natural Sciences, Växjö University, S-351 95 Växjö, Sweden.
Tree Physiol. 1995 Jan;15(1):27-34. doi: 10.1093/treephys/15.1.27.
We investigated the interaction between indole-3-acetic acid (IAA) and ethylene in the regulation of the seasonal periodicity of tracheid production in 1-year-old balsam fir (Abies balsamea (L.) Mill.) cuttings collected at different times during the dormant period. The cuttings were left with their buds intact or were debudded and treated either apically with IAA or 2-chloroethylphosphonic acid (Ethrel) in lanolin, laterally with IAA or Ethrel in lanolin, or basally with Ethrel, Co(2+) or Ag(+) in deionized water. The treated cuttings were then cultured for up to 5 weeks under controlled environment conditions favorable for cambial growth. No change in ethylene evolution was detected during the rest-quiescence transition, when IAA-induced tracheid production increased. The induction of cambial reactivation by IAA was associated with a rise in ethylene evolution, but there was no consistent relationship among IAA concentration, tracheid number and ethylene emission. Neither Ethrel, Co(2+) nor Ag(+) affected tracheid production when applied basally, except for 10 and 100 micro M Ethrel and 100 micro M Co(2+), which were inhibitory. In contrast, ethylene evolution was promoted by Ethrel and inhibited by Co(2+), whereas Ag(+) had no effect. Similarly, applying Ethrel apically or laterally increased ethylene evolution, but did not promote tracheid production except in the treatment in which 1 mg Ethrel g(-1) lanolin was applied laterally to cuttings treated apically with 0.1 mg IAA g(-1) lanolin, and in the treatment in which 10 mg Ethrel g(-1) lanolin was applied laterally to budded cuttings. We conclude that (1) ethylene evolution is not specifically associated with IAA-induced tracheid production, (2) ethylene does not mimic the promoting effect of IAA on tracheid production, and (3) ethylene can promote tracheid production, but only when its application results in a localized unphysiologically high concentration in the cambial region, which, in turn, induces an accumulation of IAA.
我们研究了吲哚 - 3 - 乙酸（IAA）与乙烯在调节休眠期不同时间采集的1年生香脂冷杉（Abies balsamea (L.) Mill.）插条中管胞产生的季节性周期性方面的相互作用。插条保留完整芽或去芽，分别用含IAA或2 - 氯乙基膦酸（乙烯利）的羊毛脂进行顶端处理、用含IAA或乙烯利的羊毛脂进行侧部处理，或用去离子水中的乙烯利、Co(2+)或Ag(+)进行基部处理。然后将处理过的插条在有利于形成层生长的可控环境条件下培养长达5周。在从静止到休眠的转变过程中未检测到乙烯释放量的变化，此时IAA诱导的管胞产生增加。IAA诱导形成层重新激活与乙烯释放量增加相关，但IAA浓度、管胞数量和乙烯排放之间没有一致的关系。基部施用乙烯利、Co(2+)或Ag(+)时，除10和100 μM乙烯利以及100 μM Co(2+)具有抑制作用外，均不影响管胞产生。相反，乙烯利促进乙烯释放，Co(2+)抑制乙烯释放，而Ag(+)无影响。同样，顶端或侧部施用乙烯利会增加乙烯释放，但除了将1 mg乙烯利 g(-1)羊毛脂侧施于用0.1 mg IAA g(-1)羊毛脂顶端处理的插条以及将10 mg乙烯利 g(-1)羊毛脂侧施于带芽插条的处理外，均不促进管胞产生。我们得出结论：（1）乙烯释放与IAA诱导的管胞产生没有特异性关联；（2）乙烯不能模拟IAA对管胞产生的促进作用；（3）乙烯可以促进管胞产生，但只有当其施用导致形成层区域局部出现非生理性高浓度时才会如此，这反过来又会诱导IAA积累。
