Distribution of Flower Pigments in Perianth of Cattleya and Allied Genera

I. Species

Abstract

Distribution patterns of flower pigments and the shape of epidermal cells in perianth tissues in 11 genera of Laeliinae orchids were investigated in relation to flower colors.
1. The 68 species examined were classified into nine groups on the basis of differences in distribution patterns of the carotenoids and anthocyanins contained in epidermal and/or parenchymatous cells in petal tissues. Yellow and orange flowers in such species as Laelia harpophylla and L. cinnabarina contained carotenoids in both epidermal and parenchymatous cells but those of Cattleya dowiana and L. flava contained them only in parenchymatous cells. Red flowers were ascribed to the coexistence of carotenoids and anthocyanins. In Sophronitis coccinea and L. milleri carotenoids were contained in both the epidermal and parenchymatous cells but anthocyanins only in the epidermis, while L. tenebrosa contained anthocyanins only in the parenchymatous cells.
Purple flowers were classified into three groups according to the presence or absence of anthocyanins in the epidermal and parenchymatous cells. The purplish red flowers of most Cattleya species contained anthocyanins in the parenchymatous cells. Some exceptional Cattleyas, C. intermedia var. aquinii and C. leopoldii, contained anthocyanins in the epidermis of splashed or spotted petals. Laelia species blooming in deep purple flowers contained anthocyanins in the epidermis but those of pale flowers did not.
2. A Hunter′s diagram of the color chromaticity of petals was divided into three sections according to hue: in the first, the b/a value of yellow to orange petals was more than. 47, due to carotenoid pigmentation only; in the second, the value lay between. 47 and -.13 and the flowers were red due to both carotonoid and anthocyanin pigments with one exception (S. coccinea var. rosea); in the third, with values between -.13 and -1.0, purplish-red, so-called ‘orchid tone’, prevailed.
In petals containing carotenoids, increased chromas corresponded to greater brightness, but increased chromas caused by intensive anthocyanin coloration in petals and lips corresponded to less brightness, as exemplified in the velvety texture of the lips in Cattleyas.
3. The size and shape of the upper epidermal cells in petals and lips varied by species, but within the same genus the variations were serial; small cells were square and appeared in glossy flowers, while large ones were triangular and caused the velvety appearance. The augmented size and the change from square to triangular shape might manifest the direction of evolution. Plants with large showy flowers in such species as C. labiata, L. purpurata and Brassavola digbyana had the largest and longest epidermal cells in each genus.