CHAPTER 35 PLANT FORM WOOOOO!!!!!!!  

Meristems: They elaborate the plant body after germination - act as stem cells for plants- rapidly divide into differentiated cells that make up the plant body - two types:     - apical meristems= elongate the root and stem of plant     - lateral meristems= produce and increase in girth         - only present in vascular plants (shrubs and trees)

Apical Meristems  - located at the tips of stems and roots -  after germination, meristems produce primary tissues which becomes the primary plant body (soft shoots and roots)  - develop into three types of embryonic tissue systems     - protoderm- forms the epidermis     - procambium- produces primary vascular tissue     - ground meristem- differentiates further into ground tissue (Think of the plant as if its still an embryo, these are the developmental stages of plant life)

Lateral Meristems - lateral meristems produce what is called secondary growth= most of the trunk, branches, and older roots of trees - has the most dramatic effect in woody plants which have two lateral meristems     - cork cambium- produces the cork cells of the outer bark     - vascular cambium- produces secondary vascular tissue and lies between the xylem (wood) and phleom (cells close to woods surface)  - interesting fact: removing the bark of a tree damages the phloem and may eventually kill the tree

Organization of the Plant Body -- coordination of primary and secondary growth produces an adult plant - plants do not have a fixed size and vary between plants, even of the same species - number, size, structure, and location of leaves is dependent on plant environment - vascular plants have a root system ( grounds them and provides the plant with ions) and a shoot system (the stem, leaves, flowers, and fruit) - nodes and internodes on the shoot develop axillary buds that create new growth -

Types of Plant Tissue: Dermal Tissue -Epidermal cells cover all the primary plant body - a number of specialized cells occur at the epidermis - guard cells flank the stomta (epidermal openings)      - contain chloroplast     - stomata only occur on the epidermal tissue of leaves     - exchange of CO2 and O2 occur at stomata - Trichomes- hair like outgrowths of the epidermis (the "fuzzy stuff" on stems and leaves)     - keep leaf surfaces cool and reduce transpiration      - some secrete sticky or toxic substances - Root hairs- occur at the tips of young roots     - keep the root in close contact with soil and increase absorption efficiency  - in vascular plants, the cork cambium produces bark which replaces the epidermis

   

Types of Tissue: Ground Cells - Parenchyma cells: most common type of cell, less specialized, mainly store food and water in large vacuoles - Collenchyma cells: relatively flexible, provide support for plant organs so they can bend without breaking (the strings of celery) - Scelrenchyma cells: two types     - fibers= long slender cells grouped in strands     - sclereids= form in branched bundles - cell wall of scelrenchyma cells contain ligin- branched polymer that causes the cell wall to become rigid

   

Types of Tissue: Vascular - xylem cells: principle water conducting tissue of plants - a combination of dead hollow cells that make vessels and trachieds - water and other ions travel from the roots through the xylem to the leaves and diffuses as water vapor out of the stomata - Phloem cells: principal food conduction tissue of plants - carried out by sieve cells and sieve-tube members - sieve-tube memebers form sieve tubes and each cell is pared with a parenchyma cell (called compaion cells) -connected by plasmodesmata- which supplies the plant cells with organic materialsr

Root Structure -there are three types vegetative organs in plants;        - roots, stems, and leaves -there are four parts recognized in developing roots;         -root cap, zone of cell division, the zone of elongation,                        and zone of maturation    -apical initials divide the cells that divide and end up on the tip become root cap cells -the other cells divide in opposite directions and pass through the three zones then they are fully differentiated       

   

The Root Cap -the root cap consist of two types of cells; columella cells (the inner cells) and root cap cells (the outer cells) -the root cap cells are continuously replenished by the root apical meristem -there are golgi bodies in the root cap cells that secretes a slimy substance, this helps the root through the soil. It also helps with the growth of nitrogen-fixing bacteria -the root cap also functions as the perception of gravity -the inner (columella) cells are very specialized               -they have endoplasmic reticulum in the nucleus and the periphery which is located in the middle or top of the cell          -contain no large vacuoles          -contain amyloplasts which form on the sides of the cells towards the pull of gravitiy                 

The Zone of Cell Division -apical meristem is located in the center of the root tip , it is shaped like a inverted concave dome -cells divide every 12 to 36 hours at the edge of the dome -these new daughter cells go to one of the three tissues; protoderm, procambium, or ground meristem -in this section genes have been identified -the inner cell layer regulates the flow of water, the outer cell layer acts as storage -if a mistake occurs and a cell is not in the correct place the cell will develop according to the new postition  

The Zone of Elongation -the cells from the primary meristem become several times longer than they are wide, this causes the root to lengthen -the vacuoles inside these cells increasing until they occupy 90% of each cell -cells do not grow anymore in size above the zone of elongation

The Zone of Maturation -the cells that elongated in the zone of elongation are differentiated into specific cell types -many epidermal cells develop roots hairs, increasing surface area to absorb nutrients and water -the ground meristem produces parenchyma cells, they are found in the interior of the epidermis         -this layer called the cortex can by many cell layers thick and it functions in storage -the endodermis has walls filled with suberin, suberin is produced in bands called Casparian strips -the stele is everything inside of the endodermis -the primary xylem conducts water

Modified Roots -most plants either produce tap roots or fibrous roots, however there are plants with roots specific to the function needed for that plant -a root that comes from something other than a root is called a adventitious root         

Stem Structure: External Form -the shoot apical meristem produces stem tissue that creates bulges (primordia) these bulges will form into leaves, shoots, and flowers -a node is the area where the leaf is attached -the area between two nodes is called an internode -the bud that is a product of the primary shoot apical meristem is called the axillary bud -a leaf scar is from the leaves falling off the trees in the fall, a bundle scar is where the vascular connections were

   

   

Internal Form -from the apical meristem  three primary meristems develop; the protoderm,the ground meristem, and the procambium  -cells of the vascular cambium divide indefinitely and create a secondary tissue

Leaf External Structure - two morphological groups-  microphyll- one gapless vein, and megaphylls- several veins - leaves have evolved to have a  flattened blade and slender stalk - mutant leaves have been found to never flatten

Leaf Blades - compound leaves= divided into leaflets  - simple leaves= undivided - compound leaves= divided into leaflets     - pinnate= lined leaflets     - palmate= radial leaflets - alternate leaves have  one bud per leaf - compound leaves have two leaves per bud  

   

Leaf Internal Structure - entire surface covered with transparent epidermis and cuticle, lower epidermis contains stomata and guard cells - two layers of tissue ( the palisade and spongy mesophyll) rest between the upper and lower epidermis  - veins, stomata, and intercellular spaces function together for gas exchange  

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