Botany for Gardeners

“A rainbow’s spectacle reveals that sunlight is composed of several colors.Of these, red and blue are captured by chlorophyll, whereas carotene andxanthophylls intercept only the blue-green part of the visible spectrum. AtIn autumn-colored leaves, chlorophyll molecules break down, unmasking the yellowcarotene and xanthophylls. Some leaves, such as those of liquidambar (left), turn redwhen anthocyanin pigments add the final touch to the tree’s colorful spectacle.The inherited color patterns of leaf variegation result from the various pigments occurringseparately or in combinations in mesophyll cells. Shown here are striped inch plantwavelengths represented by these colors, the energy of light is transferred,via the pigments, into the synthesis of foods.Artificial illumination is only effective if it provides the blue and redwavelengths absorbed by chloroplast pigments. Ideally, incandescent bulbs,which radiate abundant red, should be supplemented with selected fluorescenttubes radiating blue wavelengths. To achieve photosynthetic yieldscomparable to those in natural conditions, several lights are needed to providehigh intensities, but care must be taken to control the build-up of heat.”

“The suction of transpirational pull places water under tension in thexylem of an actively transpiring plant. Thus, when stems are cut, air isdrawn into the exposed vessels and blocks the flow of water. In the garden,flower stems should always be cut longer than desired, and recut to the correctlength while holding the stems under water. If the stems are thenquickly transferred to a vase, the transpiration stream continues uninterrupted,without the blossoms wilting. Scissor-type pruning shears or asharp knife should be used to make clean cuts so the ends of the xylem vesselsremain open.”

“When water freezes it expands; in cells, ice crystals can tear the protoplasm apart.”