Developmental and Structural Section
Lersten, Nels R. , Horner, Harry T. .
Initiation and progression of the calcium oxalate pattern in developing Prunus virginiana (Rosaceae) leaves.
Most calcium oxalate crystal research deals with individual crystal cells and subcellular events. This present study may be the first to describe how an entire foliar macro pattern (types and arrangements of all crystals) is initiated and develops. Leaves removed from dormant and expanding buds, and later leaf stages through autumn shedding, were bleached, cleared, and viewed microscopically in while mounts between crossed polarizers. Prunus virginiana (choke-cherry) stems have only druses (spherical aggregate of crystals). Bud scales have only prismatics (cuboidal single crystals). Crystals appear first as an apical cluster of prismatics in stipules about 100 Ám long, next to their larger, crystal-free, leaf blade primordium. A cluster of 3-8 prismatics then forms at the apex of about a 500 Ám leaf blade; these crystals remain unchanged while prismatics in growing stipules continue forming basipetally. The petiole is initiated next, and druses form in continuity with those of the stem. Only in the 1.1 to 1.5 cm leaf blade do the next prismatics appear, in scattered palisade mesophyll cells throughout the young lamina. When a leaf blade reaches 2-4 cm in length, the druses reach the petiole apex and begin to form along the base of the midvein. In a 4-5 cm leaf blade, the druses approach the midvein tip and also enter the lower main lateral veins. These druses are tiny and they occur in many short discrete files of cells. The lamina prismatics have been multiplying and growing much more robustly. During leaf growth from 5 to 11 cm (maximum leaf length) by mid-May, some additional druses form in the next smaller orders of veins. From mid-May to October, prismatics continue growth in mesophyll cells. Druses appear in most minor veins only after leaf maturity, many becoming large with conspicuous cores. Just-shed and overwintered leaves retain all crystals.
1 - Iowa State University, Bessey Microscopy Facility, Ames, Iowa, 50011, USA
Presentation Type: Paper
Location: Alpine A (Snowbird Center)
Date: Wednesday, August 4th, 2004
Time: 4:15 PM