Plant Tissue Root Stem Leaf

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  24 PP LLAATTSS  TT IISSSSUUEESS   Classification of plants according to their complexity of their body:a)   unicellular – their body contains 1 eukaryotic cell that is responsible for all living functions b)   multicellular – their body is composed of groups of cells of the same type associate together to form tissues , the cells in a tissue act together to perform common function Histology – is the study of the microscopic structure plant and animal tissue Classification of plant tissues  According to their function & structure: 1.   Ground tissue (is classified according to the thickness of the cell wall)  a.   parenchyma  -   its cells are usually loosely packed, cubed-shaped or elongated-   cells contain a large central vacuole and have thin,flexible cell walls   -   fills internal parts of the plant’s organs-   may be adapted for storage, support, photosynthesis-   e.g. onion bulb, mesenchyme of leaf    b.   collenchyma  -   their cell walls are irregular in shape and thickened atthe corners to provide strength and flexibility   -   support the growing parts of plant   -   e.g.  stem of the fruits of pumpkin or cucumber, stem of  potato, stem of dead nettle   c.   sclerenchyma -   sclerenchyma cells have thick, rigid cell wall-   support the non-growing parts of the plants-   e.g.  pit of plum, apricot   -   there are two types of cells:i.    fibres = cells up to 50 cm long that occur instrands, e.g. linen, flax  ii.   sclereids = thick wall lignified cells that causegritty texture of a pear  2.   Vascular tissue -   carries water and nutrients throughout the plant and helps support the plant-   are typical for higher plants in which they form vascular bundles  -   there are two kinds of vascular tissue:a.   xylem  -   moves water and minerals upward from roots to leaves-   is composed of two types of cells:i.   tracheids – are long, thick, narrow sclerenchymacells with thin separations between themii.   vessel elements – are short, wide sclerenchymacells with no end walls; are wider than tracheidsand more water move through them  Angiosperms   → contain tracheids and vessel elements Gymnosperms   → contain only tracheids   they conduct water when they are deadand empty   alive, containchloroplasts in thecells  25 they are vital cells b.   phloem -   moves sugar or sap in both directions throughout the plant srcinating in the leaves-   contains:i.   sieve tubes – are stacked to form long sievetubes with perforated end walls called sieveplates  ii.   companion cells    – are parenchyma cells thatenable sieve tube tubes to function Types of vascular bundles: 1.   concentrical vascular bundle2.   collateral vascular bundle3.   bicollateral vascular bundle4.   radial vascular bundle    3.   Protective tissue = Dermal tissue -   forms the outside covering of the roots, stems and leaves-   its cell are arranged closely together , there are no intercellular spaces-   has protective function ã   above the ground = epidermis →prevents the plant from drying out byreducing water loss from evaporation, also secretes waxy layer calledcuticle ã    below the ground = rhizodermis → protects the root, forms root hairs  that absorb water and nutrients-   special structures are derived from epidermis for keeping some specific functionsa.   cuticle – thin waxy layer over the epidermis which helpsto reduce water loss b.   stoma/ stomata  – openings in the epidermis that regulatethe passage of gases and moisture into and out of the plant, contain chloroplastsc.   hydathodes – water excreting epidermal structures,thatare formed from the stomata which lost the irability toopen and closed.   trichome = hair - are epidermal outgrowthsi.   glandular –   pelargonium  ii.   stinging –  nettle  iii.   absorptive –    root hair    4.   Meristematic tissue -   contains cells continuously divide → are responsible for plant growth-   forms meristems = growing regions of plants Classification of meristems according to their location: Classification of meristems according to their ability to divide: ã   primary meristems -   derived from apical meristems-   have ability to divide during whole lifea.   dermatogen = protoderm - gives rise to epidermis   b.    plerom – gives rise to vascular cylinder  = stele  c.    periblem    – gives rise to  primary cortex   ã   secondary meristems -   are derived from differentiated cells of mature tissue-   restore their ability to dividea.   vascular cambium – produces vascular tissue – secondaryxylem and phloem b.   corc canbium – produces cork (bark) ã   latent meristem = “resting” meristem  -   is activated during the special conditions, e.g.  pericycle → produceslateral roots  PP LLAATT  OO R R GGAASS   Classification of plant organs according to their function: 1.   vegetative –  roots, stems   and leaves – they provide nutrition and growth 2.   generative –  flowers, seeds and fruits – they provide the production of gametes Root -   root = RADIX-   roots are structures that usually grow underground  Functions : ã   to anchor the plant in the soil   ã   to absorb water, minerals and oxygen from the soil   ã   to transport water and nutrients from the soil to the rest of the plant   ã   to store energy reserves for the plant   ã   gas exchange    Root anatomy:   1 = root cap   –    is a protective covering of the root tip –     produces a slimy substance that functionslike lubricating oil which allows root to moveeasily through the soil as it grows 2 = root tip  –    contains apical meristem 3 = rhizodermis  –     protective tissue of the root –    forms root hairs 4 = cortex  –    is composed of parenchyma cells withnumerous air spaces –    storage place for starch or other metabolites 5 = vascular cylinder = stele  –    is the core of the root –    contains: o    pericycle = 7  o    phloem = 8 o    xylem = 9 o    pith = 10   6 = root hair  –    root hairs are tiny, hairlike structures –    increase the absorpting surface of a rootsystem pith rays = vascular rays (stržňové lúče)radial vascular  bundle
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