Solymosi Katalin, Bóka Károly, Böddi Béla
Department of Plant Anatomy, Eötvös University, Pázmány P. s. 1/C, Budapest, H-1117, Hungary.
Tree Physiol. 2006 Aug;26(8):1087-96. doi: 10.1093/treephys/26.8.1087.
An accompanying paper reports the accumulation of photoactive protochlorophyllide (Pchlide) in the innermost leaf primordia of buds of many tree species. In this paper, we describe plastid differentiation, changes in pigment concentrations and spectral properties of bud scales and leaf primordia of horse chestnut (Aesculus hippocastanum L.) from January until the end of bud break in April. The bud scales contained plastids with grana, stroma thylakoids characteristic of chloroplasts and large dense bodies within the stroma. In January, proplastids and young chloroplasts were present in the leaf primordia, and the fluorescence spectra of the primordia were similar to those of green leaves except for a minor band at 630 nm, indicative of a protochlorophyll(ide). During bud break, the pigment concentrations of the green bud scales and the outermost leaf primordia increased, and Pchlide forms with emission maxima at 633, 644 and 655 nm accumulated in the middle and innermost leaf primordia. Depending on the position of the leaf primordia within the bud, their plastids and their pigment concentrations varied. Etio-chloroplasts with prolamellar bodies (PLBs) and prothylakoids with developing grana were observed in the innermost leaves. Besides the above-mentioned Pchlide forms, the middle and innnermost leaf primordia contained only a Chl band with an emission maximum at 686 nm. The outermost leaf primordia contained etio-chloroplasts with well-developed grana and small, narrow-type PLBs. These outermost leaves contained only chlorophyll forms like the mature green leaves. No Pchlide accumulation was observed after bud break, indicating that etiolation of the innermost and middle leaves is transient. The Pchlide forms and the plastid types of the primordia in buds grown in nature were similar to those of leaves of dark-germinated seedlings and to those of the leaf primordia of dark-forced buds. We conclude that transient etiolation occurs under natural conditions. The formation of PLBs and etio-chloroplasts and the accumulation of the light-dependent NADPH:protochlorophyllide oxidoreductase are involved in the natural greening process and ontogenesis of young leaf primordia of horse chestnut buds.
一篇随附论文报道了许多树种芽的最内层叶原基中光活性原叶绿素酸酯（Pchlide）的积累情况。在本文中，我们描述了从1月到4月底芽萌发结束期间七叶树（Aesculus hippocastanum L.）芽鳞片和叶原基的质体分化、色素浓度变化以及光谱特性。芽鳞片含有具有基粒、叶绿体特征性的基质类囊体以及基质内大的致密体的质体。1月份，叶原基中存在前质体和幼叶绿体，叶原基的荧光光谱与绿叶相似，只是在630 nm处有一个小峰，表明存在原叶绿素（酸酯）。在芽萌发期间，绿色芽鳞片和最外层叶原基的色素浓度增加，并且在中间层和最内层叶原基中积累了发射峰分别在633、644和655 nm的Pchlide形式。根据叶原基在芽内的位置，其质体和色素浓度各不相同。在最内层叶片中观察到带有原片层体（PLB）的黄化叶绿体和带有发育中基粒的前类囊体。除了上述Pchlide形式外，中间层和最内层叶原基仅含有一个发射峰在686 nm的叶绿素条带。最外层叶原基含有具有发育良好基粒和小的、窄型PLB的黄化叶绿体。这些最外层叶片仅含有与成熟绿叶一样的叶绿素形式。芽萌发后未观察到Pchlide积累，这表明最内层和中间层叶片的黄化是短暂的。自然生长芽中叶原基的Pchlide形式和质体类型与黑暗中萌发的幼苗叶片以及黑暗处理芽的叶原基相似。我们得出结论，在自然条件下会发生短暂黄化现象。原片层体和黄化叶绿体的形成以及光依赖的NADPH：原叶绿素酸酯氧化还原酶的积累参与了七叶树芽幼叶原基的自然变绿过程和个体发育。
