Botany · Ch 10 — Secondary Growth
Secondary Phloem
Secondary Phloem
The vascular cambial ring produces secondary phloem, also called bast, on its outer face - the counterpart, on the food-conducting side, to the secondary xylem produced on the inner face. Like secondary xylem, secondary phloem has two tissue systems: an axial (vertical) system, derived from the cambium's fusiform initials and made up of sieve elements, phloem fibres and phloem parenchyma, and a radial (horizontal) system, derived from the ray initials and made up of the phloem rays. Unlike secondary xylem, however, secondary phloem is a living tissue throughout its functional life, and that life is comparatively short - it stays alive only for as long as it actively transports soluble organic compounds made during photosynthesis to the rest of the plant, after which it is crushed and replaced by newer phloem as the stem continues to thicken. Secondary phloem fibres, extracted commercially as bast fibres, are economically important - flax (Linum usitatissimum), hemp (Cannabis sativa), sun hemp (Crotalaria juncea) and jute (Corchorus capsula …
What this figure shows. A four-panel montage (a-d) illustrating commercial/economic uses and derivatives of wood. Panel (c) is captioned as a microscope slide - a 60-year-old holotype flatworm specimen (Lethacotyle fijiensis) permanently mounted in Canada balsam, a resin obtained from wood - and panel (d) is captioned 'Ant inside blastic amber', an insect trapped in fossilised tree resin (amber), which the surrounding text explains is valued as a gemstone and used in jewellery and folk medicine. NOTE ON RECOVERY: panels (a) and (b) are not individually captioned in the extracted source text and could not be identified with certainty; this cover should be vi …