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Unifacial Cambium
The unifacial cambium (pl. cambia or cambiums) 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. 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 The lycophytes, when broadly circumscribed, are a vascular plant (tracheophyte) subgroup of the kingdom Plantae. They are sometimes placed in a division Lycopodiophyta or Lycophyta or in a subdivision Lycopodiophytina. They are one of the oldest ... tr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Xylem
Xylem is one of the two types of transport tissue in vascular plants, the other being phloem. The basic function of xylem is to transport water from roots to stems and leaves, but it also transports nutrients. The word ''xylem'' is derived from the Ancient Greek word (''xylon''), meaning "wood"; the best-known xylem tissue is wood, though it is found throughout a plant. The term was introduced by Carl Nägeli in 1858. Structure The most distinctive xylem cells are the long tracheary elements that transport water. Tracheids and vessel elements are distinguished by their shape; vessel elements are shorter, and are connected together into long tubes that are called ''vessels''. Xylem also contains two other type of cells: parenchyma and fibers. Xylem can be found: * in vascular bundles, present in non-woody plants and non-woody parts of woody plants * in secondary xylem, laid down by a meristem called the vascular cambium in woody plants * as part of a stelar arrangement n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vascular Cambium
The vascular cambium is the main growth tissue in the stems and roots of many plants, specifically in dicots such as buttercups and oak trees, gymnosperms such as pine trees, as well as in certain other vascular plants. It produces secondary xylem inwards, towards the pith, and secondary phloem outwards, towards the bark. In herbaceous plants, it occurs in the vascular bundles which are often arranged like beads on a necklace forming an interrupted ring inside the stem. In woody plants, it forms a cylinder of unspecialized meristem cells, as a continuous ring from which the new tissues are grown. Unlike the xylem and phloem, it does not transport water, minerals or food through the plant. Other names for the vascular cambium are the main cambium, wood cambium, or bifacial cambium. Occurrence Vascular cambia are found in all seed plants except for five angiosperm lineages which have independently lost it; Nymphaeales, Ceratophyllum, Nelumbo, Podostemaceae, and monocots. A few ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Woody Plants
A woody plant is a plant that produces wood as its structural tissue and thus has a hard stem. In cold climates, woody plants further survive winter or dry season above ground, as opposite to herbaceous plants that die back to the ground until spring. Characteristics Woody plants are usually either trees, shrubs, or lianas. These are usually perennial plants whose stems and larger roots are reinforced with wood produced from secondary xylem. The main stem, larger branches, and roots of these plants are usually covered by a layer of bark. Wood is a structural tissue that allows woody plants to grow from above ground stems year after year, thus making some woody plants the largest and tallest terrestrial plants. Woody plants, like herbaceous perennials, typically have a dormant period of the year when growth does not take place, in colder climates due to freezing temperatures and lack of daylight during the winter months, in subtropical and tropical climates due to the dry seas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phloem
Phloem (, ) is the living biological tissue, tissue in vascular plants that transports the soluble organic compounds made during photosynthesis and known as ''photosynthates'', in particular the sugar sucrose, to the rest of the plant. This transport process is called translocation. In trees, the phloem is the innermost layer of the bark (botany), bark, hence the name, derived from the Ancient Greek word (''phloiós''), meaning "bark". The term was introduced by Carl Nägeli in 1858. Structure Phloem tissue consists of conducting Cell (biology), cells, generally called sieve elements, Ground tissue#Parenchyma, parenchyma cells, including both specialized companion cells or albuminous cells and unspecialized cells and supportive cells, such as fibres and sclereids. Conducting cells (sieve elements) Sieve elements are the type of cell that are responsible for transporting sugars throughout the plant. At maturity they lack a Cell nucleus, nucleus and have very few organelles, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lycophyte
The lycophytes, when broadly circumscribed, are a vascular plant (tracheophyte) subgroup of the kingdom Plantae. They are sometimes placed in a division Lycopodiophyta or Lycophyta or in a subdivision Lycopodiophytina. They are one of the oldest lineages of extant (living) vascular plants; the group contains extinct plants that have been dated from the Silurian (ca. 425 million years ago). Lycophytes were some of the dominating plant species of the Carboniferous period, and included tree-like species, although extant lycophytes are relatively small plants. The scientific names and the informal English names used for this group of plants are ambiguous. For example, "Lycopodiophyta" and the shorter "Lycophyta" as well as the informal "lycophyte" may be used to include the extinct zosterophylls or to exclude them. Description Lycophytes reproduce by spores and have alternation of generations in which (like other vascular plants) the sporophyte generation is dominant. Some lycophyte ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plant Physiology
Plant physiology is a subdiscipline of botany concerned with the functioning, or physiology, of plants. Closely related fields include plant morphology (structure of plants), plant ecology (interactions with the environment), phytochemistry (biochemistry of plants), cell biology, genetics, biophysics and molecular biology. Fundamental processes such as photosynthesis, respiration, plant nutrition, plant hormone functions, tropisms, nastic movements, photoperiodism, photomorphogenesis, circadian rhythms, environmental stress physiology, seed germination, dormancy and stomata function and transpiration, both parts of plant water relations, are studied by plant physiologists. Aims The field of plant physiology includes the study of all the internal activities of plants—those chemical and physical processes associated with life as they occur in plants. This includes study at many levels of scale of size and time. At the smallest scale are molecular interactions of photosynthesi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
