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Plant Cell Types and Tissues

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1 Plant Cell Types and Tissues
Exercise 5 Plant Cell Types and Tissues

2 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

3 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

4 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

5 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

6 b. Parenchyma – uniformly thin-walled
Function: for food storage Examples: cassava pith, tomato fruit pulp, Spanish flag petiole

7 c. Collenchyma – with unevenly thickened walls
- function: for strengthening & support and sometimes for storage - examples: lotus petiole, celery petiole, coleus petiole

8 d. Sclerenchyma – with heavily thickened walls because of the presence of lignin
function: for strengthening & support Examples: mungbean seed coat, peanut pericarp, pineapple leaf

9 e. Cork – outermost tissue of leaves and roots of woody dicot plants
- function: for protection

10 2. Complex Permanent Tissue
1. Phloem – conducts dissolved organic food materials Sieve tubes Companion cells Arranged end to end Shorter, narrower, vertically elongated Denucleated when matured Nucleated even when matured 2. Xylem – conducts water Tracheids – without perforations Vessel elements – with perforations

11 Accessory cells – participate in osmotic changes involved in movements of the guard cells

12 Closed Stomata Open Stomata

13 Exercise 6 Absorption Tap Root Fibrous Root

14 Modification & function
Specialized Roots Specimen Modification & function Camote Enlarged fleshy root for food storage Radish Carrot Rhizophora Brace roots for support Pandan Prop roots for support *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

15 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

16 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.

17 4. Petiole – or leaf stalk - holds the blade upright 5
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

18 8. Axillary bud – located at the leaf axil 9
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

19 Modified Stems: Plant Specimen Modification Fern plant, Ginger
Rhizome for food storage Gabi Corm Potato (Solanum tuberosum) with “eyes” = buds Tuber for reproduction Bermuda Grass Runner/Stolon Bougainvillea Thorn for protection Dilang-baka Cladophyll Vine Tendril Cycas Spines for protection

20 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

21 2. Blade or lamina – thin, flattened, green structure 3
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

22 Petiolule – stalk of each leaflet
Stipels – outgrowths in pairs found at the base of petiolule Rachis – continuation of the petiole

23 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

24 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

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