Parts of Plants and their Functions Objectives Note

Parts of Plants and their Functions

Objectives • Note contributions of plants to the life cycle on earth • List and describe the purpose of the four main parts of plants • Explain process of photosynthesis • Explain process of respiration • Explain major structural differences between dicot and monocot stems • Describe process of pollination

Importance of Plants • Without plants, life on earth would not exist • Plants are the source of food for humans and animals, directly or indirectly • Plants produce oxygen and are the major producers • Plants help keep us cool, renew the air, slow wind, hold soil in place, shelter wildlife, beautify space, perfume the air, furnish building materials, and fuel

ROOTS

Root Functions • Anchor the plant and hold upright • Absorb water and minerals from the soil and conduct them to the stem • Store large quantities of plant food • Propagate or reproduce some plants • The first three are essential to all plants

Root Structure • The internal structure of a root is similar to a stem • Older roots of shrubs and trees have a phloem on the outside, a cambium layer, and xylem (wood) on the inside • A phloem is the old outer layers of corklike bark

• The phloem carries manufactured food down to the root for food and storage • The xylem carries water and minerals up to the stem

• External structures of roots are different form stems • Roots have a root cap that produce new cells which lubricate a path and protect the cap as new roots push its way through the soil

• Behind the root cap are many root hairs which absorb moisture and minerals for larger roots and the stem • Side roots of increasing size form as the plant grows older

• Roots are important agricultural cash crops • Carrots, beets, radishes and sweet potatoes are roots • Roots also serve for propagation • Dahlia, peony, and sweet potato have tuberous root clumps that can be separated will sprout new roots and plants

Fibrous Roots • Fibrous root plants are very easy to transplant • Roots are smaller, shorter and more compact, allowing more roots to be saved

Tap Roots • Tap root systems have longer and fewer roots • Tap roots are usually cut off during transplanting which loses root hairs and the ability absorb water and nutrients • Tap roots will conduct and store water and nutrients but not absorb it

• Roots will move toward moisture in the soil • Central roots grow downward because of the force of gravity • This is know as geotropism and is controlled by the root tip

Types of Stems • Herbaceous – soft tissue that bends (ex: houseplants) • Woody – brittle, non-bendable, bark-like tissue (ex: trees, shrubs)

Functions of Stems • Transport materials up and down the plant through the vascular system ü Consists of xylem and phloem tissue ü Herbaceous stems have vascular bundles, which consist of both xylem and phloem ü Woody stems have a vascular cylinder in which the outer portion is the phloem and the inner portion is the xylem

Herbaceous Stem Woody Stem

Xylem Tissue • Moves water and nutrients UPward from the roots to the stems and leaves Phloem Tissue • Moves water and nutrients DOWNward from the stems and leaves to the roots

Other Functions of Stems • Provide physical support for leaves, flowers, and fruit • Store food (ex: onions, garlic, potatoes) • Green stems have chlorophyll in them and conduct minor photosynthesis • Capable of reproduction • Help establish tendrils which aid climbing plants

Underground stem that grows horizontally Ex: Iris, Ginger Enlarged stem that grows underground Ex: Potato Threadlike leafless growth on a stem that attaches itself to other stems/objects Ex: Sweet pea Underground food storage consisting of flat, fleshy leaves with roots on lower side Ex: Onion Above ground stem that grows horizontally Ex: Strawberry Food storage structure at the end of a stem that grows underground Ex: Gladiolus

Leaves

The Plant Body: Leaves • FUNCTION OF LEAVES o Leaves are the solar energy and CO 2 collectors of plants. o In some plants, leaves have become adapted for specialized functions.

EXTERNAL ANATOMY • Leaves possess a blade or lamina, an edge called the margin of the leaf, the veins (vascular bundles), a petiole, and two appendages at the base of the petiole called the stipules.

EXTERNAL ANATOMY

Phyllotaxy - Arrangement of leaves on a stem

Leaf types - Simple, compound, peltate and perfoliate • Simple leaf = undivided blade with a single axillary bud at the base of its petiole. • Peltate leaves = petioles that are attached to the middle of the blade; examples include mayapple • Perfoliate leaves = sessile leaves that surround are pierced by stems; examples include yellowwort and thoroughwort Yellow Wort Mayapple

Leaf types – Pinnately & Palmately Compound Leaves • Compound leaf = blade divided into leaflets, leaflets lack an axillary bud but each compound leaf has a single bud at the base of its petiole o pinnately-compound leaves: leaflets in pairs and attached along a central rachis; examples include ash, walnut, pecan, and rose. o palmately-compound leaves: leaflets attached at the same point at the end of the petiole; examples of plants with this leaf type include buckeye, horse chestnut, and shamrock.

Venation = arrangement of veins in a leaf • Netted-venation = one or a few prominent midveins from which smaller minor veins branch into a meshed network; common to dicots and some nonflowering plants. o Pinnately-veined leaves = main vein called midrib with secondary veins branching from it (e. g. , elm). o Palmately-veined leaves = veins radiate out of base of blade (e. g. , maple). • Parallel venation = characteristics of many monocots (e. g. , grasses, cereal grains); veins are parallel to one another. • Dichotomous venation = no midrib or large veins; rather individual veins have a tendency to fork evenly from the base of the blade to the opposite margin, creating a fanshaped leaf (e. g. , Gingko).

Venation Types Netted or Reticulate Venation

Leaf – Internal Anatomy

Specialized or Modified Leaves • Cotyledons: embryonic or "seed" leaves. First leaves produced by a germinating seed, often contain a store of food to help the seedling become established. • Tendrils - blade of leaves or leaflets are reduced in size, allows plant to cling to other objects (e. g. , sweet pea and garden peas. • Shade leaves = thinner, fewer hairs, larger to compensate for less light; often found in plants living in shaded areas. • Drought-resistant leaves = thick, sunken stomata, often reduced in size o In American cacti and African euphorbs, leaves are often reduced such that they serve as spine to discourage herbivory and reduce water loss; stems serve as the primary organ of photosynthesis. o In pine trees, the leaves are adapted to living in a dry environment too. Water is locked up as ice during significant portions of the year and therefore not available to the plant; pine leaves possess sunken stomata, thick cuticles, needle-like leaves, and a hypodermis, which is an extra cells just underneath the epidermis

Specialized or Modified Leaves • Prickles and thorns: epidermal outgrowths on stems and leaves (e. g. , holly, rose, and raspberries; Hypodermic trichomes on stinging nettles. • Storage leaves succulent leaves retain water in large vacuoles. • Reproductive leaves, (e. g. , Kalanchöe plantlets arise on margins of leaves. • Insect-trapping leaves: For example: pitcher plants, sundews, venus flytraps, and bladderworts have modified leaves for capturing insects; All these plants live under nutrient-poor conditions and digest insect bodies to obtain nitrogen and other essential nutrients. • Bracts: petal-like leaves. • Window Leaves: plant is buried in soil with transparent part exposed to light. Being buried reduces loss of war in arid environments. • Flower pot leaves: Structure to catch water and debris for nutrient collection - fairy-elephant's feet.

Cotyledons or “seed leaves”

Tendrils Garden Pea

Leaves as Needles and Spines

Leaves as Colorful Bracts

Flower Pot Leaves Fairy Elephant’s Foot

FLOWERS

Important Parts of a Flower • 4 main parts o o Sepal Petal Pistil (or carpel) Stamen

Sepals • Protect flower while developing from bud • Look like green little leaves • Collectively called CALYX

Petals • • Member of COROLLA All the petals make the corolla Brightly colored part of a flower Corolla and calyx make up perianth o Used to attract pollinators

Female Parts: PISTIL • Sits on the receptacle • Made of 4 parts: o o Stigma Style Ovary Ovule

Female Parts Continued • Stigma o Where pollen grains attach to • Style o Long filament structure o Prevents pollen contamination • Ovary o Protects ovule; becomes fruit when fertilized • Ovule o Becomes seed when fertilized

Male Parts: STAMEN • 3 parts o Anthers o Connective o Filament

STAMEN cont… • Anthers o Produce pollen o Contains thousands of pollen grains o Pollen contains male sex cells • Filament o Holds the anthers o Fine and hair like

Other Flower Parts • Receptacle o The part of the flower that holds everything together • Peduncle (pedicel) o Stalk of the flower

• • Types of Flowers Imperfect Perfect Complete Incomplete

Perfect Flower • Has both Pistil (Female) and Stamen (Male) • Examples: o Lilies, Roses, dandelions, wheat, apple, tomato

Imperfect flower • Has ONLY one type of reproductive organs o STAMEN OR PISTILS • Requires 2 flowers (1 male, 1 female) to reproduce • Examples: o Corn o Cucurbit family • Melons, gourds, cucurbits (cucumbers)

Male vs. Female Corn

Male vs. Female Cucurbit

Complete Flower • Has all 4 parts o Sepals, petals, pistil, stamen • All complete flowers are perfect, but not all perfect flowers are complete. Why? ? ?

Complete Flower • Examples: o Roses, zinnia

Incomplete Flower • Lacks one or more of the 4 parts • Examples: • Cucurbitaceae family o Melons, gourds, cucurbits (cucumbers) • Calla lily

Monoecious • 2 options: o Plant has perfect flowers (both sexes) o Plant has separate male and female flowers located on the same plant • Examples: o Easter Lily, pea, dandelion, rose

Dioecious • Has imperfect flowers on separate plants • One plant is male, one plant is female o Need 2 plants to reproduce • Examples: o Cucurbitaceae family

Monocot • • Embryo growth with single cotyledon Flower parts in multiples of 3 Major leaf veins run parallel Stem vascular bundles scattered Roots are adventitious Secondary growth absent Pollen with single pore

Dicot • • Embryo growth with 2 cotyledons Pollen with 3 pores Flower parts with multiples of 4 or 5 Stem vascular bundles in a ring Roots develop from radicle Secondary growth present Major leaf veins are netted