12.1: CHARACTERISTICS OF PLANTS

What are the basic needs of a plant?

1. Energy  (from sunlight)

2. Nutrients (from roots/soil)

3. Water (from root/soil)

4. Gas exchange (from leaves/stems → photosynthesis; from roots →stomata)

5. Protection from herbivores and diseases (thorns, poison, etc)

6. Reproduction (from seed, pollen, cones, fruit, flowers, spores)

How do plants capture energy?

They capture energy from incoming solar radiation and convert it into chemical energy through photosynthesis:

• 6CO2 (g)+ 6H2O(l)C6H12O6 (s)+6O2 (g)

• Carbon dioxide + water glucose + oxygen

• Plants are autotrophic.

What is glucose?

Glucose is a simple sugar and the primary source of energy for most living organisms. It is a carbohydrate that is produced during photosynthesis in plants.

What is a carbohydrate?

A Carbohydrate is a molecule that contains only atoms of carbon, hydrogen, and oxygen in a ratio of 1:2:1.

* Carbohydrates are the main source of chemical energy plants need for maintenance, growth, and development.

Nutrient Adaptions Of Plants

Plants need nitrogen, phosphorus, and potassium to synthesize proteins, lipids, and other compounds needed in their cells.

* Plants have a symbiotic relationship with Mycorrhizal fungi that are attached to their roots. This allows them to extend their surface area and absorb nutrients and water. They give plants nutrients and moisture in the soil in exchange for glucose.

Capturing Light Adaptations Of Plants

Because capturing light is an important process in photosynthesis, plants have developed different methods of maximizing capturing light. For example, some plants adjust the position of their leaves to maximize their exposure to sunlight. This process is called **phototropism**.

Protection From Herbivores Adaptations

Since plants are primary producers, they are the food source of many species. Since they can’t move away from herbivores, plants produce toxic or bad-tasting substances to keep herbivores away. Others produce tough, hairy, or prickly outer layers.

Gas Exchange Adaptations

Plants need gas exchange for cellular respiration and photosynthesis.

• In vascular plants, the gas exchange happens in the leaves.

• CO2 (g) for photosynthesis

• O2 (g) for cellular respiration

What are the four types of tissues in plants?

1. Dermal tissue: for protection

2. Vascular tissue: for transportation

3. Ground tissue: for support/structure/storage/photosynthesis

4. Meristematic tissue: for growth

Dermal tissues

**Description:** Two tissue types: epidermis and periderm Outermost cell layers often have thicker cell walls covered with a waxy cuticle

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**Role:** Protect against injury, herbivores, disease, and water loss.

Vascular tissues

**Description:** Two tissue types: xylem and phloemXylem—thick-walled cells, dead at maturityPhloem—thin-walled cells, living at maturity

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**Role:** Transport water and nutrients to support the plant body.

Ground tissues

**Description:** Three tissue types: Parenchyma—thin-walled cells, living at maturity, perform photosynthesis Collenchyma—thick-walled cells, living at maturity Sclerenchyma—cells with lignin in their cells walls, dead at maturity

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**Role:** Perform cellular processes to support growth and development (parenchyma and collenchyma)Store carbohydrates, especially starch (parenchyma)Support and protect plant body (collenchyma and sclerenchyma)

What are the three major groups of vascular plants?

1. Lycophytes

• A seedless vascular plant.

• Ex: club mosses

2. Gymnosperm

• A vascular plant that produces seeds in special structures called cones

• Ex: Pine trees

3. Angiosperms

• A plant that produces flowers.

• Ex: roses, orchids, jasmine, etc.

• Monocots and Eudicots are types of angiosperm plants.

What is phototropism?

Meristematic tissue

It is a tissue consisting of dividing undifferentiated cells (meristematic cells) found in areas of the plant where growth can take place. The meristematic cells eventually specialize. It is only present in vascular plants.