Plant Organ Analysis

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Plant Organ Analysis by Mind Map: Plant Organ Analysis

1. Leaves

1.1. Main site of photosynthesis in a plant is in the green leaves that have lots of chlorophyll and chloroplasts in the leaves.

1.2. Leaves are adapted in many different shapes and sizes to account for (a)biotic factors of survival.

1.3. Are connected to the plant at points called nodes. The distance in between these nodes is the internode.

1.4. Leaves may also connect to nodes by a petiole, or small leaf stalk.

1.5. Guard Cells and Stomata

1.5.1. The stomata are small openings in the epidermal layer of the plant that allow for transpiration and gas exchange.

1.5.2. The opening of these is regulated by specialized epidermal cells called guard cells which react to concentrations of water and gas in the leaf.

1.6. Mesophyll

1.6.1. Makes up the bulk of what is inside the leaf between the top and bottom layers.

1.6.2. Is the main site for photosynthesis.

1.6.3. Palisade mesophyll layer.

1.6.3.1. The cells are closely packed and shaped like a defensive castle wall. These have many chloroplasts and are excellent at trapping light to perform photosynthesis.

1.6.4. Spongy mesophyll layer.

1.6.4.1. These cells are strangely shaped and have many air gaps around them. Ideal for carbon dioxide and oxygen diffusion in and out of the leaves.

1.7. Adaptations to Abiotic Factors

1.7.1. These adaptations include many things that the leaf may do to adapt to weather and light conditions they must live in such as:

1.7.1.1. Evolving to have broader leaves to survive in shadier areas

1.7.1.2. Being evergreen in regions with short growing seasons to avoid wasting energy replenishing all leaves annually.

1.7.1.3. Having pines as leaves to prevent water loss, even though it makes photosynthesis less effective.

1.8. Adaptations to Biotic Factors

1.8.1. This refers to leaves that have developed any sort of specialization that allows them to escape the wrath of herbivores. This may include:

1.8.1.1. Toxins like those in the milkweed plant that poison insects and large herbivores alike.

1.8.1.2. Spiny specialized leaves as in cacti

1.8.1.3. Leaves that don't taste good or aren't appealing to herbivores.

1.9. Different types of plants:

1.9.1. Xerophyte

1.9.1.1. Thrives in areas with little moisture available.

1.9.2. Mesophyte

1.9.2.1. Plant that thrives in an area with moderate moisture.

1.9.3. Hydrophyte

1.9.3.1. A plant that lives on or in water.

2. Roots

2.1. Primary Root

2.1.1. First main root that stems out of the plant.

2.2. Secondary Roots

2.2.1. Also known as lateral roots

2.2.2. Smaller roots branching sideways outwards from the primary root.

2.3. Taproots

2.3.1. Stem further downwards than laterally.

2.3.2. Found in plants that will need to go deeper into the ground to reach a water source.

2.4. Fibrous roots

2.4.1. Many more lateral roots that will not reach as far downwards into the ground.

2.4.2. Typically found in plants that will need to spread wider to get more water near the surface (rainwater, etc.)

2.5. Vascular Bundle

2.5.1. Found in the very centre of the roots, surrounded by the endodermis, which is the innermost layer of the cortex and it regulates the lateral movement of materials in the roots.

2.6. Pericycle

2.6.1. Surrounds the vascular cylinder and is what creates lateral roots.

2.7. Can be very large and may even be larger than the shoot system in its entirety

2.8. Crucial for nutrient absorption, water absorption, rooting the plant into the ground, storage of sugars and creation of hormones used throughout the plant.

3. Tissues

3.1. Dermal Tissue

3.1.1. Includes the:

3.1.1.1. Epidermis

3.1.1.1.1. Outermost layer on the plant body.

3.1.1.1.2. Creates the cuticle through secretions

3.1.1.1.3. Often has many specialized cells on it, such as the root hairs or leaf guard cells

3.1.1.2. Periderm

3.1.1.2.1. In plants that exhibit extensive secondary growth, the periderm replaces the epidermis as the outermost layer.

3.1.1.3. Cuticle

3.1.1.3.1. A waxy, noncellular layer created by the epidermis that works to prevent excessive water loss and protect against infection.

3.2. Ground Tissue

3.2.1. Parenchyma

3.2.1.1. Succulents

3.2.1.1.1. Usually found in cacti and plants in desert climates, these specialized parenchyma are built for water storage.

3.2.1.2. Pith

3.2.1.2.1. Used to describe most of the centre content of a plant. Consists of spongy parenchyma cells and stores water, carbohydrates and nutrients.

3.2.1.3. Cortex

3.2.1.3.1. The parenchyma cells that surround the pith for more rigid support.

3.2.1.4. Made up of living tissue.

3.2.2. Sclerenchyma

3.2.2.1. Often has a secondary cell wall consisting of cellulose and lignin.

3.2.2.2. The purpose of this is to provide support or hardness and durability to certain parts of the plant where it's needed (cactus spines, nut shells)

3.2.2.3. Most mature sclerenchyma cells are dead.

3.2.3. Collenchyma

3.2.3.1. Consists of living cells that are specialized to provide support to plant areas that require protection and flexibility. Specialized by their thickened cell walls.

3.2.3.2. Celery stalks have a lot of collenchyma cells.

3.3. Vascular Tissue

3.3.1. Xylem

3.3.1.1. Main tissue in plants for conducting water and minerals upwards.

3.3.1.2. Contain tracheids and vessels which are fibres and water-conducting cells.

3.3.1.3. These cells are dead at maturity, but continue to perform their functions.

3.3.1.4. Wood is primarily xylem tissue.

3.3.2. Phloem

3.3.2.1. Mature phloem is a living tissue.

3.3.2.2. Primary function is to transport nutrients and solutes throughout the plant to sinks where they are required.

3.3.2.3. Contain highly porous sieve tubes which allow for effective and unobstructed transport of required materials.

4. Stems

4.1. The main functions of the stem are to:

4.1.1. Provide support for the plant.

4.1.2. Link the shoot system to the root system.

4.1.3. Store nutrients for the plant.

4.2. Herbaceous Stems

4.2.1. Are stems that are green, thin, and don't contain much wood. They are usually very small and help photosynthesize.

4.2.2. Will regularly be found in smaller plants.

4.2.3. Tend to be very short-lived, thus don't grow past one year.

4.3. Woody Stems

4.3.1. Found in most trees and any plants with lots of wood (not herbaceous).

4.3.2. Look like herbaceous stems in the first year, but unlike them, they continue secondary growth and keep growing laterally.

4.4. Primary Growth

4.4.1. In all stems, primary growth will occur at the apical meristems.

4.5. Secondary Growth

4.5.1. Occurs in the vascular cambium, where the dead secondary xylem becomes wood and adds a new layer of wood to the plant every year.

4.6. Stem Adaptations

4.6.1. Stems can have many different types of adaptations to serve different purposes, such as:

4.6.1.1. Tubers: a special type of underground stem used for storage and asexual reproduction.

4.6.1.2. Runners: little stems that grown laterally along the ground.

4.6.1.3. Hollow stems: in order to house symbiotic insects.