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Exercise 5. Plant Cell Types and Tissues. Tissue – group of cells that perform a specific function. 2 kinds of tissues (state of development): 1. Meristematic tissues/ meristerms - responsible for the production of new cells 2. Permanent tissues - perform specific functions.
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Exercise 5 Plant Cell Types and Tissues
Tissue – group of cells that perform a specific function 2 kinds of tissues (state of development): 1. Meristematic tissues/ meristerms - responsible for the production of new cells 2. Permanent tissues - perform specific functions
Kinds of meristems based on their position or location: 1. Apical meristem – responsible for the increase in length of stems or roots - at tips or apices of stems and roots - with very small or no vacuole at all - very thin-walled and isodiametric Includes: • Protoderm • Ground meristem • Procambium
2. Lateral meristem 3. Intercalary meristem – at bases of young leaves and internodes - for further lengthening of stems and leaves far away from the tips of stems
Kinds of Permanent Tissues: 1. Simple permanent tissues - consist only of one kind of cell a. Epidermis – outermost tissue of leaves, stems and roots of all monocots and herbaceous dicot - has a layer of cuticle made up of waxy substance called cutin to prevent excessive evaporation of water - uniseriate when young, multiseriate when old
b. Parenchyma – uniformly thin-walled • Function: for food storage • Examples: cassava pith, tomato fruit pulp, Spanish flag petiole
c. Collenchyma – with unevenly thickened walls - function: for strengthening & support and sometimes for storage - examples: lotus petiole, celery petiole, coleus petiole
d. Sclerenchyma – with heavily thickened walls because of the presence of lignin • function: for strengthening & support • Examples: mungbean seed coat, peanut pericarp, pineapple leaf
e. Cork – outermost tissue of leaves and roots of woody dicot plants - function: for protection
2. Complex Permanent Tissue 1. Phloem – conducts dissolved organic food materials • 2. Xylem – conducts water • Tracheids – without perforations • Vessel elements – with perforations
Accessory cells – participate in osmotic changes involved in movements of the guard cells
Open Stomata Closed Stomata
Exercise 6 Absorption • Tap Root • Fibrous Root
Specialized Roots *brace roots – aerial roots arising from the main stem which penetrates the ground *prop roots – aerial roots arising from the branches which penetrate the ground
Exercise 7 Transport & Nutrition • Origin of the stem: from the epicotyl and partly from the hypocotyl of the embryo • Shoot – a stem with leaves • Shoot system – all the stems and leaves of a plant
General Features of the Stem: 1. Node – where leaves, branches & buds arise 2. Internode – portion between 2 consecutive nodes 3. Leaf sheath - in some monocotyledons (Poaceae/ Gramineae/ grass family), a distinct petiole is lacking. Instead, the blade is supported by a flattened structure called the leaf sheath, which clasps the stem.
4. Petiole – or leaf stalk - holds the blade upright 5. Leaf scar – mark left on the stem by a fallen leaf 6. Bundle scar – cut end of vascular bundles seen within each leaf scar 7. Leaf axil – angle formed by the leaf stalk and the stem
8. Axillary bud – located at the leaf axil 9. Terminal bud – located at the tip of the stem 10. Bud scale – protective scale that covers the bud 11. Lenticels – tiny raised pores on dicot stems for gaseous exchange
Exer 7 Leaf • Important Terms: 1. Phyllotaxy – system of leaf arrangement on the stem: a. Alternate or spiral – only 1 leaf develops at each node b. Opposite – 2 leaves develop opposite each other at a node c. Whorled – 3 or more leaves develop equidistantly around the node
2. Blade or lamina – thin, flattened, green structure 3. Leaf stalk or petiole – holds the blade upright; to provide maximum exposure *sessile – leaf without petiole 4. Stipules – a pair of outgrowths at base of some dicotyledonous leaves *exstipulate – without stipules
Petiolule – stalk of each leaflet • Stipels – outgrowths in pairs found at the base of petiolule • Rachis – continuation of the petiole
5. Nature of leaf blade • Simple leaf – blade consists of only 1 piece • Compound leaf – blade is divided into separate segments called leaflets or pinna
6. Venation – arrangement of vein of a leaf blade • Netted or reticulate venation – veins branch profusely and form a network over the blade; commonly found in dicot leaves • Parallel venation – veins do not form a network; commonly found in monocot leaves