Module 15: Kingdom Plantae: Physiology and Reproduction March 31, 2016 Honors Biology Module 15: Kingdom Plantae: Physiology and Reproduction March 31, 2016

Class Challenge Sing a Song!

Identify the following: 6. Is this a monocot or dicot cross section?

Answers Epidermis Vascular bundle Phloem Xylem Cortex Monocot

Plant Physiology Physiology is the study of life processes in an organism. Why do plants need water? Some plants need more and others need less.

Water is used for Four Processes: Photosynthesis Turgor pressure Hydrolysis Transport We have discussed all of these processes before during the year.

Module 5: Photosynthesis Is how a plants makes its own food By using Carbon Dioxide and Water to make glucose. So without water, the plant would not be able to manufacture its own food.

Module 6: Turgor Pressure In a plant cell, there is a large central vacuole that fills with water by osmosis. As more and more water fills the vacuole, the cell becomes pressurized. This pressure is called Turgor Pressure. This keeps the plant (especially the stems) stiff. This is why plants wilt when deprived of water.

Turgor pressure Is responsible for some flowers opening their flower petals during the day and closing at night. This is also known as nastic movement that is a plant’s response to a stimulus such that the direction of the response is preprogrammed and not dependent on the direction of the stimulas.

Examples of Nastic movement Crocus flower opens at temperatures of about 60 degrees or higher and it closes at temperatures lower that that. Evening primrose flower opens at dusk due to changes in turgor pressure that are triggered by a change in the amount of light the plant receives.

Module 6: Hydrolysis When a cell takes in larger molecules, it must first break them down into smaller molecules in order to use them. The cell accomplishes this by adding water to the larger molecules. In the presence of specialized enzymes, the addition of water will break down the large molecules. If a plant manufactures too much Glucose it is stored as starch. When a plant needs it, it then can be broken down by hydrolysis for food.

Although water is used for photosynthesis, turgor pressure and hydrolysis, most water is used by the plant for transportation. Plants need more than carbon dioxide and water to live. Plant cells must carry on all sorts of biosynthesis, which requires a lot of raw materials. They are absorbed from the environment and transported throughout the plant. The raw materials are dissolved in water and the water carries them up the xylem. This requires transpiration

Water Absorption A vascular plant absorbs water by its roots. A vascular plant cannot absorb water by its leaves. It can absorb water vapor through its leaves if its stomata are open. Most vascular plants have their roots in the soil, so most roots absorb water from the soil.

How does water actually move in a plant? The xylem provide a path for the water to travel just like our veins and arteries. But plants don’t have a “water pump like a heart. So….. That still does not answer the question, “How does it move?”

Scientists are not completely sure! The theory is called cohesion-tension theory. It says that transpiration causes the water to move up the xylem of the plant. In Module 10 transpiration is defined as the evaporation of water from the leaves of a plant. In transpiration, water actually evaporates out of the inside of a leaf. It does this because in order to have carbon dioxide for photosynthesis, the leaves must have their stomata open. Water is then exposed to the air and the water begins to evaporate.

How does evaporation cause transpiration? Water has a very strong tendency towards cohesion. Cohesion is the phenomenon that occurs when individual molecules are so strongly attracted to each other that they tend to stay together, even when exposed to tension

Figure 15.2 Cohesion is the attraction that like- molecules have for each other. Let’s have an example to further explain cohesion. Last paragraph….

Now cohesion has its limits… If most animals went walking on the water they would sink. So the strength of cohesion between the water molecules must be greater than whatever force is trying to pull them apart from one another.

When Water Evaporates From the leaves, there is a deficit of water. This causes tension which pulls up on the water molecules just below where the deficit of water exists. These water molecules, in response to the tension, move up to replace the evaporated water molecules. The water molecules near the ones that move up do not want to be separated. Because of cohesion these water molecules keep moving up to stay near the ones that have moved up. This results in a “chain reaction,” with all water molecules moving upwards due to cohesion.

The Cohesion-Tension theory explains how substances move upwards through the xylem in a plant, it does not explain how substances travel throughout the plant in the phloem. This process is called translocation.

Translocation Is the process by which organic substances move through the phloem of a plant. Water and minerals need to travel up the plant (xylem). The substances produced from photosynthesis (glucose) need to move down from the leaves to nourish stems and roots. (phloem) Remember some plants store food in their roots (starch).

Translocation

Cells that make up xylem die when they mature Cells that make up xylem die when they mature. Xylem are simply tubes to allow water to flow. Phloem cells need to be alive because they actively expend energy to guide the flow of the organic molecules throughout the plant.

Plant Control http://youtu.be/HdwIcIkSoBY

Flower Dissection https://youtu.be/ZbEj5Hy3NHE

Experiment 15.1 Flower Anatomy Object: To observe various types of flowers and compare their differences and similarities.

Parts of a Flower

Homework Module 15 Read pages 478 – 490; Answer OYO questions 15.1 – 15.11; Answer Study Guide Questions a-j and 2-8; Finish Experiment 15.1 in lab book; Quiz: Parts of Flower Class Challenge: Arm Wrestling