Dictionary > Metaphloem


noun, plural: metaphloems
A component of the primary phloem that develops often following the differentiation of the protophloem
Vascular plants have vascular tissues that are responsible for the conduction of food materials, water, and nutrients to different plant parts. The complex permanent tissues include the xylem and the phloem. The xylem is the vascular tissue that conducts water and minerals from the roots upwards. The phloem is the vascular tissue that plays the role of transporting food materials (called photosynthate) from photosynthetic organs to different parts of the plant. This process is called translocation. The phloem tissues may be classified as either primary or secondary. A primary phloem is one that arises from the procambium and is involved in the primary growth (i.e. growth in length) of plants whereas a secondary phloem is one that comes from the vascular cambium during the secondary growth (i.e. growth in girth). The primary phloem is found in the primary plant body parts and occurs towards the periphery. The primary phloem has fewer phloem fibers, sieve tubes, and phloem parenchyma compared with the secondary phloem. Sclereids are also typically absent in the primary phloem.
The primary phloem is comprised of the protophloem and the metaphloem. Both the protophloem and the metaphloem arise from the procambium. However, the protophloem is the first to develop. The metaphloem may be differentiated from the protophloem in terms of cellular components and morphology. For instance, the sieve elements of the metaxylem are relatively longer, conspicuous, and with a wider lumen. The companion cells are always present in metaphloem as opposed to those in protophloem that are often absent.
Word origin: Greek prôtos (“first”) + phloem
See also:

You will also like...

The Hominids

The hominid family diversified from the apes around 6 to 8 million years ago. Since then, the evolutionary path has prov..

Psychiatry and mental disorders
Psychiatry & Mental Disorders

Different mental disorders are described here. Read this tutorial to get an overview of schizophrenia, affective mood di..

Growth and Plant Hormones
Growth and Plant Hormones

Plants, like animals, produce hormones to regulate plant activities, including growth. They need these hormones to respo..


Humans are diploid creatures. This means that for every chromosome in the body, there is another one to match it. Howeve..

genes controlling growth and development
Control of Growth & Development

Control of Growth & Development tutorials look at how the genetic makeup determines the biological processes on a da..

Plant Water Regulation
Plant Water Regulation

Plants need to regulate water in order to stay upright and structurally stable. Find out the different evolutionary adap..