Plant Structure - Senior Biology



|3.2 Organisation and the|Learning objectives |Green |Orange |Red |

|Vascular Structures | |[pic] |[pic] |[pic] |

|3.2.1 Flowering plant |Label a diagram of the external parts of a typical flowering plant | | | |

|structure and root |Shoot, root, stem, leaves, flower, fruit, seed | | | |

|structure |State the function of the root and shoot | | | |

| |Identify tap and fibrous root systems | | | |

| |Explain the term Meristem and give its location in the stem and root | | | |

| |Name and give the function of four zones in a longitudinal section of| | | |

| |a root | | | |

| |State the function of Vascular Tissue | | | |

| |Give the location of three tissue types, Dermal, Ground and Vascular, | | | |

| |in transverse sections of the of the root and stem and leaf | | | |

| |Give the location of three tissue types, Dermal, Ground and Vascular, | | | |

| |in longitudinal sections of the root and stem. | | | |

| |Identify and draw the structure of Xylem and Phloem and state their | | | |

| |function | | | |

| |Distinguish between Xylem Vessels and Xylem tracheids, and between | | | |

| |Phloem Sieve Tube Cells and Companion Cells | | | |

| |Identify Monocots and Dicots under the headings | | | |

| |Number of flower parts | | | |

| |Vein pattern in leaf | | | |

| |Arrangement of Vascular Bundles | | | |

| |Number of Cotyledons in the seed | | | |

| |Woody or Herbaceous | | | |

Practical activity

ME - Prepare and examine a transverse section of a Dicot stem under the microscope (x100, x400)

Basic structure of flowering plant:

[pic]

Functions:

Shoot system = stem, leaves, flowers and buds

• Stems – support leaves and flowers, transport water and food. May be modified - storage e.g. potato, reproduction e.g. rhizome, climbing e.g. honeysuckle, some are photosynthetic e.g. buttercup.

• Leaves – photosynthesis, transpiration, food storage, vegetative reproduction e.g. Bryophyllum plantlets.

• Flowers - reproduction

• Bud – a small compacted stem bearing tightly over-lapping leaves surrounding a growing tip – can develop into a flower, branch or maintain growth of stem. Terminal bud and axillary buds.

Stomata/lenticels – gaseous exchange

Root system = roots in soil – water and mineral absorption, anchor plant, food storage e.g. turnip, vegetative reproduction e.g. dahlia.

ROOTS

• Tap roots e.g. carrot, dandelion.

• Fibrous roots e.g. wheat.

• Adventitious roots - roots which do not develop from the radicle e.g. roots at base of an onion, and the gripping roots of an ivy.

Root- L.S.

[pic]

1. Meristematic zone: protected by root cap. Small cells with no vacuole, which divide by mitosis.

2. Zone of elongation: Cells expand (by vacuoles absorbing water) and elongate.

3. Zone of cell differentiation: Cells develop special features according to different cell types e.g. epidermis, parenchyma, vascular tissue, root hairs.

Root- T.S.

[pic]

Root Hairs - Extensions of epidermal cells, which increase surface area for absorption of water and mineral salts. No cuticle.

Dermal tissue - epidermis

Ground tissue – stores food

Endodermis - controls movement of water and minerals from ground tissue into xylem.

Xylem - transports water and minerals up to the stem.

Phloem - transports food to root.

STEM

Structure

[pic]

Herbaceous dicot stem - L.S. and T.S.

[pic]

[pic]

(Herbaceous means it has no wood. A woody stem is hard, non-photosynthetic & protected by cork. Only outer xylem conducts water.)

Dermal tissue (epidermis): Protective outer layer, + cuticle , +/- stomata, hairs.

Ground tissue: Stores food & gives strength to plant.

Vascular bundles: in a ring inside endodermis. Xylem (inside), cambium (meristematic), phloem

LEAF

External structure diagram

[pic]

• Sessile or petiolate

• Leaf type: simple (e.g. oak) or compound (lamina divided into a number of leaflets e.g. horsechestnut, ash.

• Leaf venation – reticulate (netted|) or parallel

[pic]

Plant tissues

Meristematic tissues – a region where cells are actively dividing by mitosis, producing new cells for growth.

Dermal tissues – forms and protects the surface of the plant e.g. epidermis

• Ground tissue – for support and storage

• Vascular tissue – transports water, minerals and food e.g. xylem and phloem.

1. Meristematic tissues

Structure: Living. A group of small, actively dividing cells with thin walls and no vacuoles.

Location:

Primary meristem (apical):.

Meristems, which occur in root tips, shoot tips and buds - allowing growth in length.

Secondary meristem (lateral) - allows growth in width of stems/roots. Vascular meristem causes the formation of new xylem and phloem each growing season. It makes wood and cork meristem makes cork tissue in bark.

Function: produce growth in plants by mitosis.

Lateral meristems in woody stem:

2. Dermal tissue

Structure: Outer protective tissue covering plant. Stomata in epidermis and lenticels in cork allow gas exchange.

Function:

• Protection of cells below.

• Prevent water loss and attack by m/o or insects by secreting a cuticle (made of wax and cutin – a fatty substance).

3. Ground tissue

Lies between dermal and vascular tissue e.g. mesophyll of leaves (photosynthesis), in cortex of roots and stems (food storage), pith in stems.

4. Vascular Tissue

Complex tissue i.e. composed of several types of cells.

Xylem

Function: Transport water and mineral salts from roots to leaves. Also support plant - holds up the plant against the pull of gravity.

Structure:

• Xylem vessels

Dead (no protoplasm), hollow and cylindrical usually (cells stacked end to end and cross walls broken down).

[pic]

Cellulose cell wall is strengthened to the inside with lignin(impermeable carbohydrate), may be in a pattern e.g. circular, spiral, scalariform(ladder-like), reticulate(branching) or pitted (completely lignified except for small unlignified spots). Pits allow for lateral movement of water.

• Tracheids

Elongated dead cells with fine tapering ends, fit into one another. Cross walls are pitted. Heavily lignified.

[pic]

Phloem tissue

Complex tissue composed of different types of cells.

[pic]

• Sieve tubes

Structure: Living, long, cylindrical cells, placed end to end. No nucleus. Thin, cellulose walls. Cross walls pitted and known as sieve plates.

Function: transport of food and hormones (auxins) to all plant cells from the leaves.

• Companion cells:

Structure: Living, thin-walled, long cells. Nucleus present. Lie beside sieve tubes in vascular bundles.

Controls the activities of the sieve tubes

|Monocot |Dicot |

|e.g. grasses |e.g. buttercup |

|Flowers: | |

|Flower parts occur in 3, or in multiples of 3 |Flower parts occur in pairs (or multiples |

|Outer parts of flower are bracts (unspecialised green covers) |of 2) or in 5s. |

|Flowers often wind-pollinated. |Outer parts of flower are protective (sepals) and attractive |

| |(petals) |

| |Flowers often insect-pollinated |

|Seeds: | |

|Embryo has one cotyledon - popcorn! |Embryo has 2 cotyledons (seed leaves) |

|Leaves: | |

|Leaves are long, narrow and pointed, with parallel veins. |Leaves have a broad lamina (blade) with a network of veins |

| |(reticulate). |

|Stem: | |

|Vascular bundles scattered |Vascular bundles arranged in a ring |

|No vascular meristem - no secondary thickening. |Vascular meristem - secondary thickening. |

|Root: | |

|No root hairs |Has root hairs. |

|Many small fibrous roots and adventitious roots attached | |

| |One main taproot with lateral roots. |

Practical activity

[pic]

LC questions

Section A

2005 HL

3. Indicate whether the following are true (T) or false (F) by drawing a circle around T or F.

(h) Lenticels serve the same function as stomata. T F

(i) Parallel leaf veins are characteristic of monocotyledonous plants. T F

2006 HL

1. (b) The walls of xylem vessels are reinforced with ……………………………………………………

2007 HL

6. The diagrams represent two forms of a vascular plant tissue, as seen under the microscope.

(a) Name this vascular tissue ……………………………………….

a) Identify the two forms of this tissue.

A ………………………………………………….. B ………………………………………..……

b) The walls of A and B are reinforced with a hard material. Name this material ...……………….…

c) Where precisely is this vascular tissue found in the stem of a young dicotyledonous plant?

………………………………………………………………….…………………………………...

d) Name another vascular tissue ...………………………………………………………………….....

2009 HL

5. (f) Give one location where mitosis occurs in flowering plants. _________________________

2012 HL Q5

[pic]Section B

2004 HL

8. (a) Observation of a transverse section of a dicotyledonous stem reveals vascular and other

tissues.

Name two of the tissues that are not vascular tissues.

1 …….…………………………..…………. 2 ………………..……..………………….

(b) Answer the following questions in relation to the preparation of a microscope slide of a transverse section of a dicotyledonous stem.

State one reason why you used an herbaceous stem rather than a woody one.

………………………………………………………………...………………………………

………………………………………………………………...………………………………

Explain how you cut the section.

………………………………………………………………...………………………………

………………………………………………………………...………………………………

………………………………………………………………...………………………………

………………………………………………………………...………………………………

Why is it desirable to cut the section as thinly as possible? ………………………………….

………………………………………………………………...………………………………

………………………………………………………………...………………………………

Draw a diagram of the section as seen under the microscope. Label the vascular tissues that can be seen.

State one precise function of each of the vascular tissues labelled in your diagram.

………………………………………………………………...………………………………

………………………………………………………………...………………………………

………………………………………………………………...………………………………

………………………………………………………………...………………………………

2009 HL

7. (a) (i) Why is a dicotyledonous (dicot) plant so called? ____________________________

(ii) Name a dicotyledonous plant. ___________________________________________

(b) (i) Describe in detail how you prepared a microscope slide of a transverse section of the

stem of a dicotyledonous plant.

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

___________________________________________________________________

(ii) Give an account of the procedures that you followed in order to view your slide under the microscope.

____________________________________________________________________

____________________________________________________________________

____________________________________________________________________

____________________________________________________________________

____________________________________________________________________

____________________________________________________________________

(iii) In the space below draw enough of your section to show and label the location of each of the following:

1. Phloem. 2. Xylem. 3. Ground tissue.

2011 HL

8. (iv) In the course of your practical work you prepared a transverse section (T.S.) of a dicot stem

for microscopic examination.

How did you prepare the T.S.?

__________________________________________________________________________

__________________________________________________________________________

2017 HL Q9

[pic]

[pic]

2019 HL Q9

[pic]

Section C

2005 HL

14 (a) The passage of water through a plant is known as the transpiration stream. Answer the following

questions in relation to the transpiration stream.

(iii) How is xylem adapted for its role in water transport?

2006 HL

14. (c) The diagram shows part of a transverse section through a dicotyledonous stem.

[pic]

i) Copy the diagram into your answer book and identify each of the following by placing the appropriate letter on your diagram:

phloem P, ground tissue G, xylem X, dermal tissue D.

ii) In which of the tissues that you have identified are sugars mainly transported?

iii) State a function of D.

iv) In the course of your practical work you cut and observed a transverse section of a stem.

Answer the following in relation to that procedure.

1. What did you use to cut the section?

2. How did you support the stem while you were cutting the section?

3. How did you transfer the section to a microscope slide?

(v) State one way in which a transverse section through a monocotyledonous stem differs from the one that you cut.

2008 HL

14. (c) (i) Draw a large labelled diagram of a transverse section through a young root.

2011 HL

15. (b) (i) Name the tissue in plant stems through which water rises to the leaves.

(ii) Give one way in which this tissue is adapted for the transport of water.

(iii) Give a precise location of this tissue in the stem.

(iv) State another function of the tissue referred to in (i).

2014 HL Q14

[pic]

2017 HL Q11 (a)

[pic]

2018 HL Q14 (b)

[pic]

2020 Hl Q11

[pic]

2020 HL Q15(c)

[pic]

2021 HL Q14(c)

[pic]

2022HL Q15(c)

[pic]

[pic]

Marking Scheme

2005 HL 3 (h)(i)

[pic]

2006 HL 1(b)

[pic]

2007 HL Q6

[pic]

2009 HL Q5(f)

[pic]

2012 HL Q5

[pic]

Section B

2004 HL Q8

[pic]

2009 HL Q7

[pic]

2011 HL Q8 (b) (iv)

[pic]

2017 HL Q 9 (b)(ii)

[pic]

2019 HL Q9

[pic]

Section C

2006 HL Q14 (c)

[pic]

2005 HL Q 14 (a) (iii)

[pic]

2008 HL Q14(c)(i)

[pic]

2011 Q15 (b)

[pic]

2014 Q14

[pic]

2017 HL Q11(a)

[pic]

2018 HL Q14 (b)

[pic]

2020 HL Q15(c)

[pic]

[pic]

2021 HL Q14(c)

[pic]

2022 Hl Q15(c)

[pic]

-----------------------

A

B

................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download