Plants

PLANT TISSUES ,[object Object],[object Object],Vascular Plant Form & Function cells tissue Tissue systems organs Organ systems 1.Dermal Tissue 2.Ground Tissue 3.Vascular Tissue

[object Object],[object Object],Dermal Tissue 1. Epidermal cells 2. Root Hair cells 3. Guard Cells (Leaves)

The Cuticle - a waxy coating designed to minimize water loss and act as a physical barrier against disease. Upper and Lower Epidermis – an outer layer which does not contain chloroplasts. Their thick walls are helpful for their protective function. Guard Cells – There are spaces in the epidermis called stoma which permit oxygen and water vapour to leave the leaf and carbon dioxide to enter. Each stoma has two guard cells around it, which regulate the opening and closing of the stomates. The structure of leaves is geared to ensure that photosynthesis takes place as efficiently as possible. Leaves are composed of a number of specialised cell types: Leaves

Spongy Mesophyll – active area of photosynthesis. Air spaces are between the cells and are involved in gas excange during photosynthesis. Vascular Bundles – composed mainly of xylem and Phloem. Water, minerals and other dissolved substances are conducted in the xylem, carbohydrates are conducted in the phloem. Palisade Mesophyll – these cells contain the greatest concentration of chloroplasts and is the most active area of photosynthesis.

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Roots have a number of vital jobs which are important to plants: Roots 1.Tap Roots 2. Fibrous Roots

Monocotyledons – these are fibrous roots that contain many roots of equal size. Monocotyledons also have bands of xylem and phloem around a central region. Fibrous Root System – Draw Picture Cross Section – Draw Picture Dicots – Tap Picture – Draw Picture Vascular Bundle Cross Section ,[object Object]

Root Adaptations – Depth and extent of root systems depends upon: ,[object Object],[object Object],[object Object],[object Object],Dicotyledons – These have taproot systems with vascular bundles containing xylem and phloem vessels. b) Aerial Roots – grow out from leaves to absorb oxygen c) Toxin Releasing Roots – Release substances to reduce competition

[object Object],[object Object],[object Object],Stems Primary Tissue – found in short lived herbaceous plants. This tissue is able to photosynthesise. Secondary Tissue – produces woody tissue. This tissue continues to live year after year and evolves into several tissue types. Each year produces a ring of growth.

[object Object],[object Object],[object Object],Water & Food Transport Water Transport ,[object Object]

[object Object],[object Object],[object Object],Adhesion – this is the force of attraction between unlike molecules. Water tends to become attracted to the walls of thin xylem vessels by adhesion.

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[object Object],[object Object],[object Object],[object Object],[object Object],Food Transport ,[object Object]

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In Monocotyledons – seeds develop consisting of: In Dicotyledons – the contents are much the same except that the seed contains two seed leaves (two cotyledons. ,[object Object],Seed Growth & Development ,[object Object],[object Object],[object Object],[object Object]

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Light – This is trapped by Chlorophyll and other Accessory pigments ; although only about 1% of the available light is used. ,[object Object],Day Length – This affects the quantity of light available. The photoperiod increases during the spring, is long during the summer; and decreases to a minimum during fall and winter. Day length plays a role in determining when a plant reproduces. E.g. Chrysanthemums – short days. ,[object Object],External Factors Affecting Plant Growth

[object Object],[object Object],[object Object],[object Object],Soil Nutrients Potassium Ions (K + ) Calcium Ions (Ca 2+ ) Nitrate Ions (NO 3- ) Sulphate Ions (SO 4 2- )

Light, Gravity, Reproduction, Nutrients ,[object Object],[object Object],[object Object],Hormones & the Control of Plant Growth

[object Object],[object Object],Auxins Apical Bud Growth Ripening of Fruit and Fruit Drop Cell Division

Gibberelins – Also promote cell division and elongation, particularly just before flowering occurs so that the flower is exposed to insects and wind. Cytokinins – Stimulates cell division, particularly in seeds and fruit. This has proved useful in tissue culture experiments. Ethylene – Important in fruit ripening. Growers store fruit in conditions which prevent its build up to slow down ripening. Ethylene can be added to induce ripening. ,[object Object],Abscisic Acid – Inhibits growth. This important effect stops germination during the winter.

[object Object],[object Object],[object Object],Succession

Primary Succession – This process begins when all that is present is bare rock. I.e. no living things exist, no organic material is present. ,[object Object],[object Object],[object Object]

[object Object],[object Object],[object Object],[object Object],Secondary Succession

[object Object],[object Object],[object Object],[object Object],Competition ,[object Object]

Plants

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