Chapter 13 Plant Processes

Section 1: Objectives Describe photosynthesis. Compare photosynthesis and cellular respiration. Describe how gas is exchanged in the leaves of plants. Describe two ways in which photosynthesis is important.

Capturing Light Energy Photosynthesis is the process by which plants algae, and some bacteria use sunlight. Carbon dioxide, and water to make food. Chlorophyll is a green pigment that captures light energy by photosynthesis. Chlorophyll is located in structures called grana. Grana are stacks that are found in the chloroplasts of a plant cell.

Chloroplast Structure

Capturing Light Energy The light energy captured by chlorophyll is used to help form glucose molecules. In turn, oxygen gas (O2) is given off by plant cells. Photosynthesis can be summarized by the following chemical equation:

Photosynthesis

Capturing Light Energy Glucose molecules store energy. Plants use this energy for their life processes. Cellular respiration is the process by which cells use oxygen to produce energy from food.

Gas Exchange Stomata (singular, stoma) are openings in a leaf or stem that enable gas exchange to occur. Each stoma is opened and closed by two guard cells. Transpiration is the process by which plants release water vapor into the air through stomata. If too much water is lost, a plant wilts.

Gas Exchange

Gas Exchange Plants and other photosynthetic organisms, such as some bacteria and many protists, form the base of nearly all food chains on Earth. Photosynthesis provides the oxygen that plants, animals, and most other organisms need for cellular respiration.

Section 2: Objectives Describe pollination and fertilization in flowering plants. Explain how fruits and seeds are formed from flowers. List three reasons why a seed might be dormant. List three examples of asexual reproduction in plants.

Fertilization Pollination happens when pollen is moved from anthers to stigmas. Pollen contains sperm. After pollen lands on the style, a tube grows to the ovule. Fertilization happens when a sperm fuses with the egg in the ovule.

Pollination and Fertilization

Fertilization After fertilization, the ovule develops into a seed. The ovary around the ovule becomes a fruit. What types of plants would these fruits grow on?

Seed Production

Fertilization The fruit helps protect the seed. Fruit often help spread the plant seeds. Many fruits are edible. Animals eat these fruits and discard the seeds far from the parents. Other fruits get caught on animal’ s fur or are carried by the wind.

Fertilization The young plant inside the seed stops growing once the seed is fully developed. Dormant describes the inactive state of a seed or other plant part when conditions are unfavorable to growth. What other organism have we talked about that enters a dormant stage?

Fertilization When seeds are dropped or planted in a suitable environment, the seeds sprout. Most seeds need water, air, and warm temperatures to germinate, or sprout. Each plant had an ideal temperature at which most of its seeds will begin to grow.

Germination Of A Seed

Fertilization The following methods are ways that flowering plants reproduce asexually: Plantlets Tiny plants grow along the edges of a plant’s leaves until they fall off and grow on their own. Tubers Underground stems, or tubers, can produce new plants. Runners Above-ground stems from which new plants can grow are called runners.

Chapter 13 Section1-2 Recap 1) What are grana and what do they contain? 2) What type of sugar does photsynthesis produce in plants? 3) What do glucose molecules store? 4) What is the function of guard cells? 5) What must happen before fertilization occurs?

Ch. 13 Section 1-2 Recap 6) After fertilization, what does the ovule develop into? 7) After fertilization, what does the ovary around the ovule develop into? 8) List 2 things that the fruit helps plants do. 9) When does the young plant inside the seed stop growing? 10) List 3 ways plants reproduce asexually.

Section 3: Objectives Describe how plants may respond to light and gravity. Explain how some plants respond to night length. Describe how some plants respond to the changes of season.

Plant Tropisms Tropism is the movement of all or part of an organism in response to an external stimulus, such as light. Plant growth toward a stimulus is a positive tropism. Plant growth away from a stimulus is a negative tropism.

Plant Tropisms The shoot of a plant’s tips bend toward the a source of light. Bending toward the light is a positive tropism. A change in the direction a plant grows that is caused by light is called phototropism.

Plant Tropisms Plant growth also changes in response to the direction of gravity. This change is called gravitropism. Shoot tips have negative gravitropism. They grow away from the center of the Earth. Root tips have positive gravitropism. They grow towards the center of the Earth.

Plant Tropisms The difference between day length and night length is an important environmental stimulus for many plants. This stimulus can cause plants to begin reproducing. Plants that reproduce in fall or winter are called short-day plants. Plants that reproduce in spring or summer are called long-day plants.

Night Length and Flower Color

Plant Tropisms Evergreen trees, such as pine and holly, shed leaves year round so that some leaves are always on the tree. Deciduous trees, such as maple, oak, and elm trees, lose all of their leaves each year. Deciduous trees lose all of their leaves around the same time each year.

Plant Tropisms The leaves of deciduous trees may change color before they are lost. Green chlorophyll breaks down in fall, revealing pigments that are usually hidden.

Seasonal Pigment Changes