Plant Defenses, Pollination and Angiosperm Life Cycle

• Secondary compounds help plants defend themselves.
• Plants space themselves out and attract pollinators.

Plant Defenses

• Plants have various defenses, including nectar, phenolic secretions, poison oak, and poison ivy.
• Some plants utilize ants and other insects for protection.
• Layers of bark that shred, sticky traps, and oils/saps deter critters.
• Plants with hallucinogenic or bad-smelling properties discourage animals.
• Chemical compounds and alkaline types of chemicals act as plant defenses.

Pollination

• Pollinators are attracted to flowers through nectar and other means.
• Some pollinators are drawn to scents resembling rotting corpses or feces.
• Pollen is transferred from one plant to another via pollinators.

Angiosperm Life Cycle

• Angiosperm life cycle includes both male and female parts in the flower.
• Mechanisms exist to prevent cross-pollination.
• Plants have multiple chromosomes, allowing adaptation to different morphologies.
• The flower contains male (anthers) and female (ovules) parts.
• Ovules contain megaspores and food.
• Pollen grain attaches to the stigma and divides into two sperm.
• Double fertilization: two sperm fertilize the egg and initiate endosperm development.
• Endosperm nourishes the developing baby plant.

Double Fertilization

• Double fertilization occurs when two sperm are discharged into the ovule.
• One sperm fertilizes the egg to form the baby plant (zygote).
• The other sperm combines with two nuclei to create the endosperm (food for the baby).
• The process is unique to angiosperms.
• This results in a triploid (3n) endosperm.

Angiosperms

• Double fertilization in angiosperms leads to the formation of the baby and its food source.
• Ovary around the seed attracts something to eat it.

Evolution

• The oldest known angiosperm fossil is 162 million years old from the mid-Jurassic period in China.
• Basic primitive fossils of angiosperms are often found near water.
• Male and female parts (stamens and carpals) are modified leaf structures.

Eudicots and Monocots

• Angiosperms are divided into two main groups: dicots and eudicots.
• Eudicots called "true dicots."
• Cotyledons are the first leaves of a plant.
• Dicots have two cotyledons, while monocots have one.
• Two thirds of angiosperm species aee eudicots

Plant Structures

• Magnoliids are very ancient flowering plants.
• Flowers may appear before leaves in some plants like magnolias.
• Grasses and other monocots have tiny flowers.

Plant Anatomy and Tissues

• Plants have organs composed of tissues, which are composed of cells.
• Roots rely on sugars produced by photosynthesis, while shoots rely on water and minerals from the roots.
• Roots anchor the plant, absorb minerals and water, and store organic nutrients.
• Tap root systems have a main vertical root with lateral roots (e.g., California Poppy).
• Adventitious roots arise from stems or leaves.
• Roots and fungi work together almost immediately to absorb food.
• Roots, stems, and leaves are the major plant organs

Modified Roots

• Modified roots include prop roots, aerial roots, food storage roots, and parasitic roots.
• Pneumatophores are aerial roots that help cypress trees avoid waterlogging.
• Parasitic roots (haustoria) penetrate other plants to obtain nutrients.

Stems

• A stem contains alternating nodes (where leaves attach) and internodes (between nodes).
• Roots developed coming from stems attached to the ground
• Modified stems include bulbs, corns, rhizomes, runners, tubers, tendrils, and cladophylls e.g. potatoes
• Runners grow above ground, while rhizomes grow underground.
• Tubers are underground modified stems for storage (e.g., potatoes).
• Cactuses use thorns for protection.
• Bulbous structures in plants like onions store energy

Auxiliary Definitions

• Auxiliary buds are structures with the potential to form new lateral shoots or branches.
• Apical buds are located at the tip of shoots and cause elongation.
• Apical dominance inhibits the growth of non-apical buds
• Cutting off the apical bud causes lateral buds to grow sideways.

Leaves

• The leaf is the main photosynthetic organ of a plant
• It consists of a flattened blade and a petiole (stalk).
• Leaf structure differs between monocots and dicots and arrangement of their veins.
• Monocots have parallel veins, while dicots have netted veins.
• Modified leaves include floral leaves, bracts, spines, reproductive leaves, and window leaves.
• Succulent leaves and cone-shaped leaves can allow photosynthesis.

Modified Leaves

• Plants can have modified leaves incl; tendrils, Succulent, insecticide leaves.
• Spines are modified leaves that provide protection.
• Some plants have succulents in their leaves to minimize the evaporation rate
• Plant can have window leaves that allow light in, and not let water out
• Insectivorous leaves trap insects to supplement nutrients (e.g., Venus flytraps)
• Pitcher plants are insectivorous leaves that trap insects.
• Plant can be carnivorous because Nitrogen is lacking in the soils

Plant Tissues

• Each plant organ has dermal, vascular, and ground tissue systems
• The dermal tissue consists of epidermis, and has is color coded
• Epidermis can have a waxy coating (cuticle) to prevent water loss and protect the plant (especially in drier climates)
• Ground tissue: It is essential
• Epidermis can be replaced by periderm in older plants.
• Vascular tissue is the plumbing in the plant.
• There different types of plant cells: Parenchyma, Collenchyma and Sclerenchyma.
• Vascular tissue is for water

Parenchyma Cells.

• Mature parenchyma cells have thin and flexible primary walls.
• Parenchyma tissue are fleshy parts of an apple has this tissues
• It does lack the secondary walls

Collenchyma Cells

• Collenchyma cells has thicker than the one just described(Parenchyma tissues)
• It gives the plants a little more sturdyness, and not as flimsy,
• Celery are primary example, they don't have the secondary walls

Sclerenchyma Cells

• There are rigid because of the thicker secondary cell walls, because it's strengthened with lignin, a material from wood and maturity
• At their functional maturity, the sclerenchyma cells are DEAD.
• Hemp and flax are an example,

Plant Xylem and Phloem

• The plumbing of the water in the parts, and the pholem

Explore plant defenses such as nectar, secretions, and symbiotic relationships with insects. Learn about pollination, including how plants attract pollinators through scents and nectar. Understand the angiosperm life cycle, covering male and female parts, and mechanisms to prevent cross-pollination.