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Roots, Stems & Leaves.

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Presentation on theme: "Roots, Stems & Leaves."— Presentation transcript:

1 Roots, Stems & Leaves

2 Roots, Stems & Leaves Specialized Organs & tissues in plants – plants do not have organ systems – Fig. 23-2 Roots – anchors plant, takes up water and minerals, provides protection from bacteria & fungi, some specialized for food storage Stems - provide support, transport substances, provide protection Leaves – site of photosynthesis, prevent water loss (guard cells & cuticle), area of gas exchange

3 Roots, Stems & Leaves

4 Roots, Stems & Leaves

5 Roots, Stems & Leaves D. Dermal tissue – “skin” of plant, outermost layer Single layer of epidermal cells Cuticle – waxy layer that slows down water loss Trichomes – speialized cells that provide protection Root hairs – specialized for water absorbtion Guard cells – found on the underside of a leaf, open & close – fig

6 Dermal Tissue

7 Roots, Stems & Leaves E. Vascular tissue – “bloodstream” of plant, specialized for transport Xylem – transports water one way – from root to leaves Composed of tracheids and vessel elements Xylem cells are dead and hollow Provide support (most of the cells of a tree trunk are dead xylem cells) Phloem – transports water and minerals in two directions Composed of sieve tube elements and companion cells cells are living

8 Vascular Tissue

9 Vascular Tissue

10 Roots, Stems & Leaves F. Ground tissue – most abundant tissue; found between dermal and vascular tissue – Fig. 23-4 Parenchyma – thin walled; function mainly in photosynthesis and storage Collenchyma – thick walled, provide support, flexible Sclerenchyma – thick walled, provide support, very rigid cell walls Where would you expect to find more scherenchyma – in the leaves or the stem of a plant? Where would you expect to find more parenchyma – in the leaves or the stem of a plant?

11 Ground Tissue

12 Roots, Stems & Leaves Meristematic tissue – “growth” tissue; made up of cells that undergo mitosis and cell division frequently – Fig. 23-5 Meristems – where cell division takes place; found only at specific locations a. Apical meristem – present in growing tips of stems and roots; accounts for an increase in length b. Cambium – increases thickness of stems & roots; gives rise to some protective (cork) & vascular tissue Not all plant cells or tissue are capable of producing new plant parts, growth is always associated with the presence of meristematic tissue

13 Meristamic Tissue

14 Meristamic Tissue **** Except for meristematic tissue, all other tissues are found continuously throughout plant organs.****

15 Roots – Fig. 23-6 Types 1. primary root – 1st structure to emerge from a seed 2. Secondary root – roots formed from tissues of

16 Roots – Fig. 23-6 B. Systems 1. taproot – primary root that grows longer and thicker than other roots 2. fibrous – numerous roots that branch to such an extent that no single root grows larger than the rest

17 Roots – Fig. 23-6 B. Systems 3. adventitous – roots that grow from stems or leaves (ex. Ivy & Spanish moss) (root growth)

18 Roots – Fig. 23-6 Root Structure and Growth – Fig. 23-7
Made up of all tissue types Epidermis & endodermis are dermal tissues Cortex is ground tissue Vascular cylinder is vascular tissue Roots are divided into various “zones” Root cap – protects meristematic tissue Meristematic zone – actively dividing cells Elongation zone – cells enlarge Maturation zone – differentiation 9cellular specialization)

19 Roots – Fig. 23-6

20 Roots – Fig. 23-6 Root Functions – anchor, absorb water and minerals
Nutrients in the soil are needed by the plant in order for it to be healthy Movement of minerals and water – both active transport & osmosis are involved in movement from soil to vascular cylinder Minerals are actively transported from a low concentration to a high concentration, requires energy This causes a difference in water between the root and soil Therefore, water moves from a high concentration in the soil to a low water concentration in the cells Casparian strip – waterproof substance that keeps substances from “squeezing” between cells of endodermis; allows endodermis to keep some substances out of vascular cylinder; ensures one way movement into cylinder

21 Roots – Fig. 23-6

22 Roots – Fig. 23-6 2. Movement of minerals and water - (con’t)
e. Root pressure – Fig 1. created by one way movement of water & minerals 2. root cells don’t expand, so as water keeps moving in it has nowhere to go but up (remember cohesion & adhesion) 3. Root pressure only accounts for water to rise approx. 1m

23 Stems – Fig Basic function is to support and transport water and minerals from the soil to the leaves

24 Stems – Fig. 23-11 A. Monocot and Dicot Stems – Fig. 22-25, 23-12
Monocot – vascular bundles are scattered; ground tissue is fairly uniform Dicot – vascular bundles are arranged in a ring; ground tissue makes up pith & cortex

25 Stems – Fig B. Primary growth – increase in length caused by cell division in apical meristem; Fig

26 Stems – Fig C. Secondary growth – increase in width caused by cell division from meristematic tissue found in vascular cambium & cork cambium – Fig Vascular cambium produces new xylem & phloem Wood is formed as xylem cells die each year and form layers or “rings” a. Heartwood – older xylem that no longer conducts water but does provide support b. Sapwood – active xylem that conducts water Bark – made up of phloem, cork cambium, & cork; cork cambium produces cork which helps protect the stem – Fig

27 C. Secondary growth (con’t)
Stems – Fig C. Secondary growth (con’t)

28 C. Secondary growth (con’t)
Stems – Fig C. Secondary growth (con’t)

29 Leaves Leaves (most) are specialized for photosynthesis
A. Structure – Fig Flat, broad to increase surface area exposed to the sun Arrangement – also maximizes exposure to the sun

30 Leaves B. Internal function & structure – Fig. 23-18, & 23-19
Cuticle – waxy outermost layer, protects & slows down water loss Epidermis – clear, with little to no pigment Stomates – exchange of oxygen and carbon dioxide; guard cells regulate opening & closing of stomates to balance water loss with rates of photosynthesis

31 Leaves Guard cells

32 B. Internal function & structure – Fig. 23-18, & 23-19
c. Mesophyll - two types 1. palisade mesophyll – tightly packed; cells contain many chloroplasts 2. spongy mesophyll – large air spaces between cells; fewer chloroplasts

33 Mesophyll

34 Leaves B. Internal function & structure – Fig. 23-18, & 23-19
d. Veins – made up of xylem and phloem tissue

35 Leaves Veins

36 Transport A. Transpiration – the evaporation of water from plant surfaces; most takes place on leaves through opened stomates – Fig B. Water transport 1. Capillary action – involves cohesion & adhesion – Fig 2. root pressure – osmotic pressure in roots caused by a buildup of solutes 3. transpirational pull – the main process bys which water moves through the xylem of a plant

37 Transport

38 Transport B. Water transport (con’t)
3. Transpirational pull – the main process bys which water moves through the xylem of a plant a. Water moves molecules exit air spaces in spongy mesophyll to atmosphere – creates negative pressure b. Lost water in air spaces replaced by water from xylem tissue c. Cohesion/adhesion keep water moving up from the roots d. Is water pulled or pushed in transpiration? 4. Regulation of transpirational is controlled by the opening & closing of stomates, which depends on light; temp; and water availability

39 Transport Nutrient transport – involves the movement of sugars from one area of a plant to another 1. Sugars move from a source to a sink

40 Transport Nutrient transport – (con’t)
2. Pressure flow hypothesis a. Sugars are actively transported from a “source” cell into sieve tubes: this causes water to follow by osmosis (from xylem to phloem) b. Seive cells in “sink” area lose sugar; this causes water to move from phloem tissue to xylem c. This water pressure gradient causes liquid in phloem to flow

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