Lersten Nels R, Horner Harry T
Department of Ecology, Evolution and Organismal Biology, Iowa State University, Ames, IA 50011, USA.
Ann Bot. 2006 May;97(5):723-9. doi: 10.1093/aob/mcl036. Epub 2006 Mar 2.
Prunus, subgenus Padus, exhibits two completely different calcium oxalate crystal macropatterns in mature leaves. Foliar macropattern development has been described previously in P. virginiana, representing one version. Prunus serotina, in the group exhibiting the second macropattern, is described here. The goal was to describe developmental details for comparison with P. virginiana, and to extend the sparse current knowledge of crystal macropatterns.
Leaves at various developmental stages were removed from local trees and from herbarium specimens. Early leaf stages and freehand leaf and stem sections were mounted directly in aqueous glycerine; larger leaves were processed whole or in representative pieces in household bleach, dehydrated in alcohol/xylol, and mounted in Permount. Crystals were detected microscopically between crossed polarizers.
Bud scales have a dense druse population. Druses appear first at the stipule tip and proliferate basipetally but soon stop forming; growing stipules therefore have a declining density of druses. Druses appear at the tip of leaves <1 mm long, then proliferate basipetally in the midrib. Lamina druses appear in the distal marginal teeth of leaves 3 cm long; from here they proliferate basipetally and towards midrib along major veins. In about two-thirds-grown leaves (6-9 cm length) druses are all adaxial to veins of most orders; a shift occurs then to formation of prisms, which appear first abaxial to, then all around, veins. Mature leaves have virtually all prisms encrusting all major veins, more sparsely along smaller minor veins. Late season leaves form epitactic crystals on existing prismatics.
The developing and mature macropattern of P. serotina is almost the reverse of the pattern described previously in P. virginiana, and shows that two closely related species can develop radically different modes of crystallization. The few detailed macropattern studies to date reveal striking variations that indicate a new level of organization that must be integrated with the anatomical, physiological and molecular approaches that have been dominant so far.
稠李亚属在成熟叶片中呈现出两种截然不同的草酸钙晶体宏观模式。此前已对弗吉尼亚稠李叶片宏观模式的发育进行了描述，代表了其中一种模式。本文描述了呈现第二种宏观模式的黑樱桃。目的是描述发育细节以便与弗吉尼亚稠李进行比较，并扩展目前关于晶体宏观模式的稀少知识。
从当地树木和标本馆标本上采集处于不同发育阶段的叶片。早期叶片阶段以及徒手切取的叶片和茎段直接置于水性甘油中；较大的叶片则整体或取代表性部分在家用漂白剂中处理，在酒精/二甲苯中脱水，然后用Permount封固。在正交偏光镜下显微镜检测晶体。
芽鳞中有密集的晶簇群体。晶簇首先出现在托叶尖端，并向基部增生，但很快停止形成；因此生长中的托叶晶簇密度逐渐降低。晶簇出现在长度小于1毫米的叶片尖端，然后在中脉向基部增生。叶片表皮晶簇出现在3厘米长叶片的远端边缘齿中；从这里它们向基部增生并沿着主脉向中脉方向扩展。在大约三分之二成熟的叶片（长度6 - 9厘米）中，晶簇大多位于大多数叶脉的近轴面；随后发生转变，开始形成棱柱体，棱柱体首先出现在叶脉的远轴面，然后围绕叶脉出现。成熟叶片几乎所有棱柱体都包裹着所有主脉，沿着较小侧脉分布较稀疏。季末叶片在现有的棱柱体上形成外延晶体。
黑樱桃发育和成熟的宏观模式几乎与先前描述的弗吉尼亚稠李模式相反，表明两个近缘物种可以发育出截然不同的结晶模式。迄今为止为数不多的详细宏观模式研究揭示了显著差异，表明存在一个新的组织层次，必须将其与迄今为止占主导地位的解剖学、生理学和分子学方法相结合。
