Organs in Plants Packet #53 Chapter #

Introduction There are four major organs of a plant Flower* (Not all plants) Stem Leaf Root

Flower

The flower contains the organs of plant sexual reproduction It attracts insects needed to carry the pollen between plants to allow pollination It's important for reproduction

Stem

The stem is the organ which holds the leaves upright in the air and facing the light It carries water and minerals to the leaves, and food around the plant The stem is important for nutrition, excretion and growth

Stem II Stem Alternating system of nodes Locations where the leaves are attached Internodes Stem segments between nodes Auxiliary Bud Angle, or axil, formed by each leaf of the stem Has the potential to form a branch Most though are dormant

Stem III Growth of a young shoot is usually concentrated at its apex (tip), where there is a terminal bud with developing leaves and a compact series if nodes and internodes The presence of terminal bud prohibits the growth of the axillary bud Apical dominance “evolutionary response that directs growth toward light

The Leaf

Leaf I The leaves are the sites of photosynthesis, gas exchange and transpiration. They make all the food that the plant needs Leaves contain chlorophyll, which uses light energy to change carbon dioxide and water into glucose They have tiny little pores, which allow essential carbon dioxide in and waste gases out Leaves are important for nutrition and excretion

Leaf II The external structure of a leaf consists of a flattened blade and a petiole Stalk Joins the leaf to the node on the stem Leaves are in various sizes, shapes and arrangement of leaves.

Variations of Leaves Simple, Pinnate Feather Shaped Simple, Palmate Palm Shaped

Variations of Leaves Simple, Cordate Heart-Shaped Simple, Orbicular Round

Variations of Leaves Pinnately Lobed Feather-Shaped Palmately Lobed Palm-Shaped

Variations of Leaves Pinnately Compound

Roots

The root is the organ which provides anchorage for the plant so that it does not blow away or fall over With its root hairs it provides a big surface area to help take in water and minerals from the soil - these are both essential for photosynthesis The root is therefore important for nutrition

Root Hairs At the tip of roots, a vast number of root hairs can be found. Why? Most absorption of materials occur near the tips of roots Increases the surface area of roots. Root hairs are extensions of epidermal cells

Adventitious Roots Roots that develop out of above ground stems or leaves are called adventitious roots These roots occur as of adventitious tissue Tissue that grows in an atypical location Provide additional support for taller plants.

Modified Roots

Modified Roots I Prop Roots Develop from branches, or a vertical stem and grow downward into the soil to help support certain plants in an upright position Fichus tree South Florida? Buttress Roots Swollen bases or braces that support certain tropical rainforest trees that have shallow root systems

Modified Roots II Pneumatophores Aerial “breathing” roots that may assist in getting oxygen to submerged roots Contractile Roots Roots that grow into the soil and then contract Pulling plant deeper into the soil Corms bulbs

Mutualistic Relationship Between Roots & Other Organisms

Relationships Mycorrhizae Mutually beneficial associations between roots and soil fungi Root nodules Swellings that develop on roots of legumes and house millions of rhizobia (nitrogen fixing bacteria) Root Graft Natural connection between the roots of trees belonging to the same or different species.

Basic Morphology of Plants

The basic morphology of plants reflects adaptations that have developed so that an organism can inhabit and obtain resources from soil and air. More to come on organ systems later.

Review