Plants: From Cells to Systems

Transcription

1 Plants: From Cells to Systems Key terms: Cell specialization Cell differentiation Tissue Organ Meristematic cell Transpiration Gall Cell specialization Cell specialization For many years, scientists wondered how cells specialized. They knew that all cells in an organism were produced through mitosis, however not all cells are identical. At some point in a cell s development, cells that start out the same undergo a differentiation process called cell differentiation. Cell differentiation Key points:

2 Specialized Cells and Tissues in Plants In living organisms, groups of specialized cells form tissues. Tissues Groups of tissues working together are called organs Organs In plants, their continued growth is a result of specialized cells called meristematic cells or meristem. Meristematic cells Meristematic cells are undifferentiated cells that can form specialized cells in plants. These cells have also been referred to as permanent embryos because of their lifelong ability to produce the cells that can become new tissues and organs in their part of the plant. Meristematic cells are responsible for creating specialized that combine to form three major types of tissues found in the body of a plant: 1) Dermal tissue

3 2) Ground Tissue 3) Vascular Tissue Vascular tissue cells: Xylem: Phloem: Repairing and replacing specialized cells The cells, tissues and organs found in multicellular animals such as worms, fish, snakes, birds and mammals are formed as the embryo develops. While some cells and tissues can be repaired and replaced, organs must last for a plants lifetime. Plants, on the other hand, are different...

4 Consider the following plant diagram: In addition to cells and tissues, plants form new organs periodically. Ex. So, why do growing plants push upward, downward, and outward? What is a bud? Where does a plants most active growth occur? What are lateral buds?

5 In general, branches and roots grow because of dividing meristematic cells. A plant s stem becomes wider because of meristematic cells in a layer called the cambium. Growing up or branching out Cells in the terminal bud produce the plant hormone auxin, which holds back plant growth in buds elsewhere in the plant. Task: How, exactly, does auxin effect the growth of lateral buds? Explain? Tissues working together: Plant organs Although human beings have many organs in their body, plants only have three or four. The three types of organs that make up the body of a plant are: i) The leaf ii) The stem iii) The root These organs are what make it possible for the plant to live and grow. The fourth organ, the flower, is a reproductive organ found in many, but not all, plants.

6 The Leaf The most important job a leaf has to provide a large surface area where photosynthesis can take place. Even those leafs that resemble thin needles, such as those found on coniferous trees, produce a large surface area because the plant has so many of them. If the plant produces more glucose than necessary, the excess is converted into starch and stored in the leaf. As a result, the rate of photosynthesis slows. As depicted above, the following diagram is that of the leaf and its internal structure. The Upper and Middle leaf

7 Lower Leaf Surface Transpiration:

8 Inside the chloroplast Characteristics: The Stem Two main functions: 1. 2.

9 Characteristics: The Roots Characteristics:

10 Tumours in Plants: Plant Galls Plant Galls Characteristics: Plant Reproduction: The flower Characteristics:

11