Unifacial cambium
Encyclopedia
The unifacial cambium produces cells to the interior of its cylinder. These cells differentiate into xylem
tissue. Unlike the more common bifacial cambium
found in later woody plants, the unifacial cambium does not produce phloem
to its exterior. Also in contrast to the bifacial cambium, the unifacial cambium is unable to expand its circumference with anticlinal cell division. Cell elongation provides a limited amount of expansion.
Due to the limited capacity for circumference growth, unifacial cambium plants had very little wood compared to modern woody plants. Xylem tissue in unifacial cambium plants was particularly structurally efficient. Additional structural support was provided in lycophytes by a special periderm tissue in the outer cortex.
Lycophyte trees exhibit determinate growth. These trees appear to have lived for most of their life cycle as a 'stump', establishing root networks underground, before shooting up rapidly, releasing spores, and dying shortly thereafter.
Xylem
Xylem is one of the two types of transport tissue in vascular plants. . The word xylem is derived from the Classical Greek word ξυλον , meaning "wood"; the best-known xylem tissue is wood, though it is found throughout the plant...
tissue. Unlike the more common bifacial cambium
Vascular cambium
The vascular cambium is a part of the morphology of plants. It consists of cells that are partly specialized, for the tissues that transport water solutions, but have not reached any of the final forms that occur in their branch of the specialization graph...
found in later woody plants, the unifacial cambium does not produce phloem
Phloem
In vascular plants, phloem is the living tissue that carries organic nutrients , in particular, glucose, a sugar, to all parts of the plant where needed. In trees, the phloem is the innermost layer of the bark, hence the name, derived from the Greek word "bark"...
to its exterior. Also in contrast to the bifacial cambium, the unifacial cambium is unable to expand its circumference with anticlinal cell division. Cell elongation provides a limited amount of expansion.
Unifacial cambium plant morphology and life cycles
The unifacial cambium allowed plants to grow as tall as 50 metres. Lacking secondary phloem, unifacial cambium plants developed alternative strategies to long range nutrient transport. For example, the stems of lycophyte trees were covered in photosynthesizing leaf bases.Due to the limited capacity for circumference growth, unifacial cambium plants had very little wood compared to modern woody plants. Xylem tissue in unifacial cambium plants was particularly structurally efficient. Additional structural support was provided in lycophytes by a special periderm tissue in the outer cortex.
Lycophyte trees exhibit determinate growth. These trees appear to have lived for most of their life cycle as a 'stump', establishing root networks underground, before shooting up rapidly, releasing spores, and dying shortly thereafter.