A close-up view of the flowering kale

Flowering Kale, although not edible, is grown for its ornamental, multi-coloured foliage. Even when not “flowering” in the botanical sense, its leaves resemble a giant, multi-petaled ruffled flower.

The plant is a member of the mustard family, (Brassicaceae). The genus Brassica is remarkable, because it contains more important horticultural and agricultural crops than any other genus. Turnips, cabbages, brussels sprouts, cauliflower, and broccoli are just a few examples.

The hybrid studied in this article derives from wild Brassica oleracea, which is native to coastal southern and western Europe, where it grows near limestone sea cliffs. This unusual habitat is due, it is believed, to its tolerance of lime and salt, but intolerance of competition from other plants.

Plant breeders have, over the years, attempted to “improve” on the wild species, by changing their growth habit, and intensifying the colour of their leaves. Brassica oleracea ‘Chidori White’ is one such cultivar. Unfortunately, many, including this one, suffer from an extreme dislike of warm weather, and so they are sold as decorative plants, solely for the spring or fall seasons. They have the advantage of coping with below freezing temperatures very well – in fact, the plants’ colouration is intensified after a frost!

The first image in the article shows a close-up view of the fringed leaf colouration in ‘Chidori White’, while the two, below, show the entire plant. I was fortunate – only one of the plants at the greenhouse was actually in bloom on that particular day!

The base and upper portion of the plant’s flower spike can be seen below. The central stem has many branching stalks from which the buds, and flowers grow. Fringed leaves are concentrated near the base of the flowering stalk.

Clusters of pale green buds are shown against a background of deeper green leaflets in the following images.

Unlike the much larger leaves beneath the flower stalk, these are not frilly at their edges. Notice the wide variation in the shape of the “teeth” along the leaflet’s edge.

Buds showing just a hint of yellow beneath the enclosing sepals (modified leaves), soon open to reveal pale yellow, four-petaled flowers.

At first, the six stamens are positioned close to one another (left image). They soon separate (right image).

The flower’s petals do not have perfectly smooth edges, particularly at their tips.

Three images follow that show a flower’s reproductive organs. Each light-brown anther (male pollen producing organ) is supported by a pale green filament. At the centre of the columnar arrangement of stamens, is a single pistil consisting of a bulbous, yellow-green stigma (female pollen accepting organ), and its supporting darker green style.

Under the microscope, one of the anther lobes, and the filament are visible.

In order to show the globular, semi-translucent cells that cover the back surface of an anther, the dark-ground condenser was moved off-centre.

Higher magnification reveals the ellipsoidal shape of individual pollen grains.

The surface cells of the filament can be seen in the photomicrograph that follows.

At the base of the centrally located pistil is the swelling that represents the top portion of the flower’s ovary (seed producing organ).

On the left below, is the image of the upper portion of the pistil. At the tip is the flattened, spherical stigma. A sturdy style supports this structure. On the right is a photomicrograph showing the small spherical cells on the stigma’s surface.

Beneath the flowering spike of the plant is the dome-shaped structure formed by the rings of Kale leaves.

Notice that a relatively narrow band at the outer edge of each leaf is ruffled. Also note the contrasting white colour of the prominent vein structure on the back of each leaf.

The following sequence of images moves up the magnification scale in order to show that the leaf structures are interesting at any magnification.

Each leaf is connected to the main stem by a short stalk. The two images below show the cellular makeup of the point where leaf and stem meet.

A lower magnification image shows different amounts of green pigmentation, (due to chlorophyll), at various locations.

Higher magnification shows the comparison between the shape of vein cells (left), and the cells that make up the rest of the leaf (right).

All Kale leaves have a very high water content. If a leaf is squeezed between cover-glass and slide, tiny water droplets are excreted that glint when illuminated.

In addition to the green–white colouration of this cultivar, many others are available including pink and lavender. However, whatever the colours, this plant is remarkable because of its structurally complex, ruffled leaves.

Photographic Equipment

All of the macro-photographs were taken with an eight megapixel Canon 20D DSLR equipped with a Canon EF 100 mm f 2.8 Macro lens which focuses to 1:1. A Canon 250D achromatic close-up lens was used to obtain higher magnifications in several images.

The photomicrographs were taken with a Leitz SM-Pol microscope (using a dark ground condenser), and the Coolpix 4500.

Further Information

Flowering Cabbage and Kale

http://www.umass.edu/umext/floriculture/fact_sheets/specific_crops/cabbkale.html

A Flower Garden of Macroscopic Delights

A complete graphical index of all of my flower articles can be found here.

The Colourful World of Chemical Crystals

A complete graphical index of all of my crystal articles can be found here.

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