| Summary: | <p>Abstract</p> <p>Background</p> <p>Histochemical staining of plant tissues with 4-dimethylaminocinnamaldehyde (DMACA) or vanillin-HCl is widely used to characterize spatial patterns of proanthocyanidin accumulation in plant tissues. These methods are limited in their ability to allow high-resolution imaging of proanthocyanidin deposits.</p> <p>Results</p> <p>Tissue embedding techniques were used in combination with DMACA staining to analyze the accumulation of proanthocyanidins in <it>Lotus corniculatus </it>(L.) and <it>Trifolium repens </it>(L.) tissues. Embedding of plant tissues in LR White or paraffin matrices, with or without DMACA staining, preserved the physical integrity of the plant tissues, allowing high-resolution imaging that facilitated cell-specific localization of proanthocyanidins. A brown coloration was seen in proanthocyanidin-producing cells when plant tissues were embedded without DMACA staining and this was likely to have been due to non-enzymatic oxidation of proanthocyanidins and the formation of colored semiquinones and quinones.</p> <p>Conclusions</p> <p>This paper presents a simple, high-resolution method for analysis of proanthocyanidin accumulation in organs, tissues and cells of two plant species with different patterns of proanthocyanidin accumulation, namely <it>Lotus corniculatus </it>(birdsfoot trefoil) and <it>Trifolium repens </it>(white clover). This technique was used to characterize cell type-specific patterns of proanthocyanidin accumulation in white clover flowers at different stages of development.</p>
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