A working knowledge of plant structure is important in order to understand how plants grow, and how environmental factors affect that growth. For this study, we will start with the smallest components and work our way up to the larger, more complex plant parts. The relationships of a cell's components can be summarized as follows: Organelles make up cells -->
Cells are the basic unit of tissues -->
Tissues combine and form organs -->
Organs make up plants|
To learn about the organelles and other components of a plant cell, take a self-test on the components and even build a plant cell, click on: Interactive Cell Structure and choose Plant Cell.
As you enjoy this interactive experience, make notes in your Plant Morphology Study Sheet. Plant Tissues
Recall that the next level of organization up from cells is the plant tissue. Plant tissue can be divided into four basic categories: meristematic tissue, ground tissue (not related to its location), vascular tissue, and dermal tissue. To learn more about each tissue type, click on the Plant Tissue Video to view a Flash presentation that explains the four tissue types. Plant Organs and Functions
The function of the roots in a plant are three-fold: anchor the plant in the soil; uptake and transport of water and nutrients; and storage of carbohydrates. Regions of the Root Tip
* Root cap - protects the dividing cells
* Zone of cell division - area where new cells are formed * Zone of cell elongation - area of water uptake and increase in volume * Zone of cell maturation and differentiation - area where vascular tissues form. Root Tissues
* Epidermis - protects the root; origin of root hair
* Cortex - location of stored carbohydrates
* Endodermis - prevents the outward movement of water from the root * Pericycle - origin of branch roots, site of water and nutrient uptake. * Xylem - transports water and nutrients
* Phloem - transports products of photosynthesis.
Root systems are primarily either tap roots or fibrous roots. The tap root is characteristic of dicot or broadleaf plants with one main root and multiple lateral roots. The fibrous root system is found in monocot plants and consist of a mass of small roots near the soil surface.
Stems provide structure the plant and also contain the transport vessels for water, nutrients, and the products of photosynthesis (photosynthate) within the plant. Stems can be modified in many ways to form some familiar structures: * Corm - enlarged and fleshy with a few leaves
* Bulb - closely packed fleshy leaves
* Tuber - enlarged underground stem with buds
* Rhizome - underground lateral stem
* Stolon - aboveground lateral stem
* Tendril - extension used for climbing
* Thorn - protrusion used for defense
Attached to the stems at specific regions known as nodes are the leaves. The regions in between the points of attachment are internodes. Not only are leaves the site of photosynthesis, but also leaves are the location for water and gas exchange. * The internal leaf structure is composed of the following elements: * Cuticle waxy barrier
* Epidermis - thick upper layer of cells
* Palisade mesophyll cells - contain chloroplasts for photosynthesis. * Spongy mesophyll cells - provide flexibility and cushioning. * Vascular bundle
* Xylem - conducts water
* Phloem - transports photosynthate
* Sclerenchyma fibers - provide support to the vascular bundle * Stomates- small pores that allow for the passage of gases * Guard cells - open and close stomate
Leaves come in many types and arrangements. Click on the Leaf Video for a better understanding of the different leaf shapes and arrangements. Wood
Horticulture is a unique discipline that has specific plants known as woody species. Therefore, it is important to understand how wood develops. Wood is considered secondary growth and the...