Stirk W A, Novák O, Václavíková K, Tarkowski P, Strnad M, van Staden J
School of Biological and Conservation Sciences, University of KwaZulu-Natal Pietermaritzburg, Scottsville, 3209, South Africa.
Planta. 2008 May;227(6):1279-89. doi: 10.1007/s00425-008-0699-z. Epub 2008 Feb 13.
Germination and seedling establishment follows a distinct pattern which is partly controlled by hormones. Roots have high levels of cytokinins. By quantifying the fluctuations in endogenous cytokinins over time, further insight may be gained into the role of cytokinins during germination and seedling establishment. Radicles were excised from sterile Pisum sativum L. seeds after 30 min and 5 h imbibition. Seedlings germinated on agar were harvested after 1, 3, 6 and 9 days. The roots were divided into the root tip, root free zone, secondary root zone and from day 6, the secondary roots. Samples were purified by various chromatographic methods and endogenous cytokinins detected by LC(+)ES-MS. Benzyladenine levels doubled after 5 h imbibition and then gradually decreased over time. Low concentrations of cis-Zeatin (cZ) type cytokinins were detected in the radicle after 30 min imbibition. After 5 h imbibition, cis-zeatin riboside-5'-monophosphate had greatly increased. The total cytokinin content of the roots increased over time with the ribotides being the predominant conjugates. From day 3 onwards, there was a gradual increase in the free bases, O-glucosides and their ribosylated forms. Mainly N ( 6 )-(2-isopentenyl)adenine (iP)-type cytokinins were detected in the root tip, whereas trans-zeatin- (tZ), dihyrozeatin- (DHZ) and iP-type cytokinins were found in the secondary roots and root zone. Cytokinin biosynthesis was only detected after day 6. Biosynthesis of iP and tZ derivatives was quite rapid, whereas biosynthesis of cZ derivatives remained at a low basal level. These fluctuations in cytokinin types and concentrations suggest the cytokinins may be synthesized from various pathways in pea roots.
种子萌发和幼苗形成遵循一种独特的模式，这种模式部分受激素控制。根中细胞分裂素水平较高。通过量化内源性细胞分裂素随时间的波动，可能会进一步深入了解细胞分裂素在种子萌发和幼苗形成过程中的作用。在无菌豌豆种子吸胀30分钟和5小时后，切下胚根。在琼脂上萌发的幼苗在第1、3、6和9天收获。将根分为根尖、无根区、次生根区，从第6天起还包括次生根。样品通过各种色谱方法进行纯化，并用液相色谱(+)电喷雾质谱法检测内源性细胞分裂素。吸胀5小时后，苄基腺嘌呤水平翻倍，然后随时间逐渐下降。吸胀30分钟后，在胚根中检测到低浓度的顺式玉米素（cZ）型细胞分裂素。吸胀5小时后，顺式玉米素核苷-5'-单磷酸大幅增加。根中细胞分裂素的总含量随时间增加，其中核糖核苷酸是主要的结合物。从第3天起，游离碱、O-葡萄糖苷及其核糖基化形式逐渐增加。在根尖主要检测到N(6)-(2-异戊烯基)腺嘌呤（iP）型细胞分裂素，而在次生根和根区发现反式玉米素（tZ）、二氢玉米素（DHZ）和iP型细胞分裂素。细胞分裂素生物合成仅在第6天后检测到。iP和tZ衍生物的生物合成相当迅速，而cZ衍生物的生物合成仍处于低基础水平。细胞分裂素类型和浓度的这些波动表明，细胞分裂素可能在豌豆根中通过多种途径合成。
