Topic 9 plant science
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Topic 9: Plant Science. Modified from S. Taylor, S. Frander and L. Ferguson. 9.1.2 Outline 3 differences between the structures of dicotyledonous plants and monocotyledonous plants.

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Topic 9: Plant Science

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Topic 9 plant science

Topic 9: Plant Science

Modified from S. Taylor, S. Frander and L. Ferguson


Topic 9 plant science

9.1.2 Outline 3 differences between the structures of dicotyledonous plants and monocotyledonous plants


Topic 9 plant science

9.1.1 Draw and label plant diagrams to show the distribution of tissues in the stem and leaf of a dicotyledonous plant.


Topic 9 plant science

Distribution of Tissues in Stem and Leaf of

Dichotyledonous Plants

  • Epidermis surrounds and contain stem/leaf organ and vascular tissue; outer layer of wax coated cells that provide protection.

  • Xylem is vascular tissue used in water transport.

  • Phloem is vascular tissue used in organic solutes transport.

  • Pith is the center of dicot plant stems; in some plants it breaks down forming a hollow stem, while in older woody plants it is filled with rigid xylem wood fiber.

  • Cambium are the single-celled layer of meristematic (dividing) tissues that continually divides to form phloem tissues toward the outside and xylem tissues toward the inside.  Cell division of the cambium tissues adds width to the stem.

  • Cortex is the primary tissues of a stem externally bound by the epidermis and internally by the phloem.Info from http://www.ext.colostate.edu/mg/gardennotes/133.html


Tissue organization of leaves

Tissue Organization of Leaves

  • The epidermis in leaves is interrupted by stomata, which allow CO2 exchange between the air and the photosynthetic cells in a leaf

  • Each stomatal pore is flanked by two guard cells,which regulate its opening and closing

  • The ground tissue in a leaf, called mesophyll, is sandwiched between the upper and lower epidermis


Topic 9 plant science

Fig. 35-18

Guard

cells

Key

to labels

Stomatal

pore

Dermal

Epidermal

cell

Ground

50 µm

Vascular

Cuticle

Sclerenchyma

fibers

Stoma

(b)

Surface view of a spiderwort

(Tradescantia) leaf (LM)

Upper

epidermis

Palisade

mesophyll

Spongy

mesophyll

Bundle-

sheath

cell

100 µm

Lower

epidermis

Cuticle

Xylem

Vein

Phloem

Guard

cells

Vein

Air spaces

Guard cells

(a) Cutaway drawing of leaf tissues

(c)

Cross section of a lilac

(Syringa)) leaf (LM)


Tissue organization of leaves1

Tissue Organization of Leaves

  • Below the palisade mesophyll in the upper part of the leaf is loosely arranged spongy mesophyll, where gas exchange occurs

  • The vascular tissue of each leaf is continuous with the vascular tissue of the stem

  • Veins are the leaf’s vascular bundles and function as the leaf’s skeleton

  • Each vein in a leaf is enclosed by a protective bundle sheath


Topic 9 plant science

9.1.3 Explain the relationship between the distribution of tissues in the leaf and the functions of these tissues.Absorption of light—parenchyma chloroplasts (ground tissue)Gas exchange stomata in epidermis--(controlled by epidermis guard cells) (dermal)Water conservation--cuticle produced by epidermis (and guard cells ) (dermal) Transport of water—xylem (vascular tissue)Transport of products of photosynthesis—phloem (vascular tissue)


Topic 9 plant science

9.1.4 Identify modifications of roots, stems and leaves for different functions: bulbs, stem tubers, storage roots and tendrils

Bulbs are vertical, underground shoots consisting mostly of the swollen bases of leaves that store food

Stem tubers are the swollen ends of underground stems that are specialized for storing food.


Topic 9 plant science

9.1.4 Identify modifications of roots, stems and leaves for different functions: bulbs, stem tubers, storage roots and tendrils

Storage roots are taproots that store food. The plant consumes this food during flowering and fruit production.

Tendrils modified stems or leaves as seen in climbing plants; provide flexible support


9 1 5 state that dicotyledonous plants have apical and lateral meristems

9.1.5 State that dicotyledonous plants have apical and lateral meristems

Meristem—plant tissue that remains embryonic for the life of the plant, allowing for growth throughout life, since they divide by mitosis.

9.1.6 Compare growth due to apical and lateral meristems in dicotyledonous plants.

Apical –primary (vertical) growth

--enables plant to reach light

Lateral--secondary (lateral) growth; form from cambium

--replaces epidermis with bark

--adds new vascular rings each year


Meristems generate cells for new organs

Meristems generate cells for new organs

  • A plant can grow throughout its life; this is called indeterminate growth

  • Some plant organs cease to grow at a certain size; this is called determinate growth

    • Annuals complete their life cycle in a year or less

    • Biennials require two growing seasons

    • Perennials live for many years

  • Meristems are perpetually embryonic tissue and allow for indeterminate growth

  • Apical meristems are located at the tips of roots and shoots and at the axillary buds of shoots

  • Apical meristems elongate shoots and roots, a process called primary growth


Secondary growth adds girth to stems and roots in woody plants

Secondary growth adds girth to stems and roots in woody plants

  • Secondary growth occurs in stems and roots of woody plants but rarely in leaves

  • The secondary plant body consists of the tissues produced by the vascular cambium and cork cambium

  • Secondary growth is characteristic of gymnosperms and many eudicots, but not monocots

  • Lateral meristems add thickness to woody plants, a process called secondary growth

  • There are two lateral meristems: the vascular cambium and the cork cambium

  • The vascular cambium adds layers of vascular tissue called secondary xylem (wood) and secondary phloem

  • The cork cambium replaces the epidermis with periderm, which is thicker and tougher


Topic 9 plant science

Fig. 35-11

Primary growth in stems

Epidermis

Cortex

Shoot tip (shoot

apical meristem

and young leaves)

Primary phloem

Primary xylem

Pith

Lateral meristems:

Vascular cambium

Secondary growth in stems

Cork cambium

Periderm

Axillary bud

meristem

Cork

cambium

Cortex

Primary

phloem

Pith

Primary

xylem

Secondary

phloem

Root apical

meristems

Secondary

xylem

Vascular cambium


9 1 7 explain the role of auxin in phototropism as an example of control of plant growth

9.1.7 Explain the role of auxin in phototropism as an example of control of plant growth

  • Auxin—a plant hormone that controls growth

  • Tropism—a plant response to an external stimulus

  • Phototropism—a plant response to light

    Proteins calledphototropinsabsorb light and bind to receptors that stimulate transcription of (growth)elongation genes in the cells, with the most auxin produced in the shaded cells.


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