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TISSUES Plant cell types rise by mitosis from a meristem. A meristem may be defined as a region of localized mitosis. Meristems may be at the tip of the shoot or root (a type known as the apical meristem) or lateral, occurring in cylinders extending nearly the length of the plant. A cambium is a lateral meristem that produces Plant tissues (usually) secondary growth. Secondary growth Meristematic produces both wood and cork (although from tissues separate secondary meristems). Primary Secondary Nonmeristematic tissues Ground Supportive Secretory Dermal Vascular Meristematic cells have thin cell walls, rich in cytoplasm, their vacuoles are small because they are young dividing cells, have large nucleus but their total size is small. Primary meristems can be found in root, shoot and branch tips. They enable growth in the length of the plant. Caliptra in root tip protects the dividing cells. Secondary meristems can be found only in dicotyledones which live for more than a year. They are responsible for growth in the width of the plant. Cambium is between the xylem and phloem. Cork cambium produces the cork layer which protects plant. Apical meristems located at the tips of roots and shoots supply cells for the plant to increase in length (grow up for shoots and down for roots) growth in this direction is known as primary growth primary growth found in herbaceous and woody plants primary growth found in monocots and dicots Lateral meristems located near the periphery of the plant, usually in a cylinder supply cells for the plant to increase in girth growth in this direction is known as secondary growth found in all woody and some herbaceous plants lateral meristems and secondary growth found only in dicots Plant cells are formed at meristems, and then develop into cell types which are grouped into tissues. Plants have only three tissue types: 1) Dermal; 2) Ground; and 3) Vascular. Plant tissues Meristematic tissues Primary Secondary Nonmeristematic tissues Ground Dermal Supportive Secretory Vascular The ground tissue comprises the bulk of the primary plant body. Parenchyma, collenchyma, and sclerenchyma cells are common in the ground tissue. Dermal tissue is composed of epidermal cells, closely packed cells that secrete a waxy cuticle that aids in the prevention of water loss. Vascular tissue transports food, water, hormones and minerals within the plant. Vascular tissue includes xylem, phloem, parenchyma, and cambium cells(in dicotyledones”. Plant tissues Nonmeristematic tissues Ground paranchyma mesophyll(photosynthetic paranchyma) vascular paranchyma paranchyma for storage paranchyma for aeration Supportive – sclerenchyma collenchyma Secretory Dermal-protective Vascular Paranchyma cells Least specialized plant cells Thin and somewhat flexible cell walls Living at maturity Carry on most of the plant's metabolic functions Generally have a large central vacuole Most parenchyma cells have the ability to differentiate into other cell types under special conditions During repair and replacement of organs after injury http://www.uic.edu/classes/bios/bios100/lectf03a m/lect18.htm Plant tissues Nonmeristematic tissues Ground paranchyma Supportive – sclerenchyma collenchyma Secretory Dermal-protective Vascular Collenchyma cells support the plant. These cells are charcterized by thickenings of the wall, the are alive at maturity. Sclerenchyma cells support the plant. They often occur as bundle cap fibers. Sclerenchyma cells are characterized by thickenings in their secondary walls. They are dead at maturity . Plant tissues Nonmeristematic tissues Ground Supportive – Secretory Dermal-protective Vascular Specialized secretory parenchymal cells are found lining resin ducts . For attraction of birds and insects, for protection, for healing Plant tissues Nonmeristematic tissues Ground Dermal-protective epidermis: The outermost layer (occasionally several layers) of cells on the primary plant body. Doesn’t have chloroplasts but they are living. Hair cells and stoma are formed from the differentiation of epidermal cells. The epidermal tissue functions in prevention of water loss and acts as a barrier to fungi and other invaders. Thus, epidermal cells are closely packed, with little intercellular space. To further cut down on water loss, many plants have a waxy cuticle layer deposited on top of the epidermal cells periderm: The outer layers of tissue of woody roots and stems, consisting of the cork cambium and the Vascular tissues produced by it, such as cork. It has lenticels for gas exchange. Plant tissues Nonmeristematic tissues Ground Dermal-protective The supporting and water-conducting tissue Vascular of vascular plants, consisting primarily of Xylem: tracheids and vessels . It has one way of flow direction. This tissue is nonliving and has long hollow tubes. The food-conducting tissue of vascular plants, consisting of sieve tubes, fibers, parenchyma, Phloem: and sclereids . This tissue is composed of living cells. It has 2 way flow of organic molecules like aminoacids and glucose or sucrose. Root Dicotyledone stem Monocotyledone stem Monıocotyledones and dicotyledones Monocotyledones Have 1 cotyledone One piece of seed Leaves are parallel veined The number of the Petals of the flowers are 3 or multiples of the 3 Vascular tissue is randomly scattered in the stem. Dicotyledones Have 2 cotyledones 2 piece of seed Leaves are net veined The number of the petals of the flowers are 4 or 5. Vascular tissue is lined in a circle in stem.