Chapter 25 Plant Response and Adaptations

What is a Plant? Plants are: ◦ Multi-cellular ◦ Eukaryotic ◦ Cell walls made of cellulose ◦ Develop from multi-cellular embryos ◦ Are photosynthetic organisms using green pigments  Chlorophyll a and b

What Plants Need To Survive Plants need: ◦ Sunlight ◦ Minerals ◦ Gas exchange ◦ Movement of water and nutrients throughout the plant body

What Do Plants Need to Survive: Sunlight Plants use energy from sunlight to carry out photosynthesis ◦ Every plant has adaptations shaped for their environment to gather sunlight ◦ Photosynthetic organs  Leaves are broad and flat and arranged on the stem.

What Plants Need to Survive: Water and Minerals Plant cells require a constant supply of water Water is a raw material of photosynthesis Minerals are absorbed with the water ◦ Minerals are nutrients in the soil that are needed for plant growth.

What Plants Need to Survive: Gas Exchange Plants require carbon dioxide and release oxygen from photosynthesis The exchange needs to take place with out a large loss of water.

What Plants Need to Survive: Movement of Water and Nutrients Take up water and minerals through their roots Make food in their leaves Specialized tissues carry water and nutrients up from soil.

Evolution of Vascular Tissue First Vascular Plants Tracheids: a great innovation of the plant kingdom. ◦ Tracheids are hollow cells with thick cell walls that resist pressure. In the plant they are connected end to end to create a straw-like design. ◦ The tracheid cells are located in the Xylem ◦ Xylem: a form of vascular tissues that carries water upward from the roots to every part of the plant

Evolution of Vascular Tissue Second Adaptation to Vascular Plants Phloem: transports solutions of nutrients and carbohydrates produced by photosynthesis. ◦ Cells are long and specialized to move fluids through the body of the plant body. Also produced lignin: a substance that makes cell walls rigid. ◦ The presence of lignin allows plants to grow tall and upright.

Evolution of Vascular Tissue Both forms of vascular tissue – Xylem and Phloem – can move fluids throughout the plant body, even against the force of gravity.

Plant Kingdom Mosses and Relatives Ferns and Relatives Cone-bearing Plants Flowering Plant

Flower Parts Stamen (male) ◦ Anther ◦ Filament Carpel (Pistil) ◦ Stigma ◦ Style ◦ Ovary ◦ Ovule

Plant Growth Respond to environmental factors: ◦ Light ◦ Moisture ◦ Temperature ◦ Gravity __________________________________ Questions???? How do plants know to grow down, how do stems know to grow towards the light? How do plants ensure that their growth is evenly balanced?

Plant Hormones Hormone: a substance that is produced in one part of an organism that affects another part of the same individual. ◦ Plant hormones are chemical substances that control a plant’s patterns of growth and development, and the plant’s responses to environmental conditions.

Hormones and Target Cells Hormones move through a plant from the place where they are produced to the place where it will trigger a response Target Cell: (target tissue) the portion of an organisms affected by a particular hormone.

Hormone  Auxin Auxin: produced by the tip of seedlings that regulate plant growth and stimulate cell elongation. ◦ Auxins are produced in the apical meristem (a group of undifferentiated cells that divide to produce increased length of stems and roots) and are transported downward into the rest of the plant.

Hormones  Cytokinins Cytokinins: a plant hormone that is produced in the growing roots and developing seeds and fruits. ◦ Cytokinins stimulate cell division and the growth of lateral buds (a group of undifferentiated cells found on the side of a stem that gives rise to side branches), and cause dormant seeds to sprout. ◦ Considered to have the opposite effect of auxins  Auxins cause cell elongation  Cytokinins cause cells to grow thicker

Hormones  Gibberellins Gibberellins: hormone that increases the size of stems and fruit.

Hormones  Ethylene Ethylene causes fruit to ripen by fruit tissues releasing small amounts of the hormone.

Tropisms Tropisms: the responses of plants to environmental stimuli. ◦ Plant tropisms include-  Gravitropism  Phototropism  Thigmotropism Each response s demonstrates the ability of plants to respond effectively to conditions in which they live.

Phototropism Phototropism: is the tendency of a plant to grow toward a source of light.

Gravitropism Gravitropism: a tendency of a plant to grow in a direction in response to the force of gravity. Half the plant responds with gravity (roots) Half the plant responds against gravity (stem)

Thigmotropism Thigmotropism: the response of plants to touch. ◦ A plant that is touched regularly may have a stunted growth. ◦ Vines and climbing plants growing around a house or fence are attracted to the feel of the object.  EX: grapes have tendrils that wrap around the object near them.

Photoperiodism Photoperiodism: plant responses to light and darkness ◦ Photoperiodism in plants is responsible for the timing of the seasonal activities such as flowering and growth. Short Day Plants: plants that flower when the period of light during the day is short. Long Day Plants: plants that flower when the period of light during the day is long.

Photoperiodism

Photoperiodism Phytochrome: this is the pigment found in plants that is responsible for photoperiodism. ◦ Absorbs red light and activates a number of signaling patheways within plant cells.

Winter Dormancy Dormancy: a period during which an organisms growth and activity is decreased or stopped. ◦ As cold weather approaches deciduous plants (plants that shed their leaves) turn off photosynthetic pathways, transport materials form leaves to roots and seal leaves off from the rest of the plant.

Leaf Abscission Leaf abscission is the process a deciduous plant undergoes to seal off the vascular tissue in the stem from the leaf. ◦ Causes the leaf to fall from the tree ◦ Occurs after chlorophyll no longer is able to absorb light.  Other pigments after chlorophyll become useful including:  Yellow and orange carotenoid  Red anthocyanins  Brown occurs when no pigments are left to absorb light