Life of a Flowering Plant Chapter 20 Life of a Flowering Plant

20.1 Reproductive Adaptations Flower is a specialized shoot with modified leaves sepals: outermost ring; covers flower bud petals: second ring; colorful to attract pollinators stamens and carpels: center ring; reproductive structures

Reproductive Structures Male Gametophytes produced in stamens anther: sac on top of stalk of stamen Spores develop into pollen grains Pollen = 2 cells with protective wall Female Gametophytes produced in carpels Ovary at base Ovules produce 4 cells each; 3 die Each undergo 3 cycles of mitosis embryo sac: resulting gametophyte style: leads to ovary stigma: sticky tip

Pollination pollination: pollen grains released from anthers land on stigma Pollen grain absorbs water and extends a pollen tube which grows toward ovary Pollen cell divides forming 2 sperm (n) One fertilizes egg = zygote (2n) = embryo The other fertilizes the central cell = (3n) endosperm

Seed Dispersal Fruits protect seeds and help disperse Travel by sticking to animal’s fur (burr) Fleshy fruit that attracts animals; seeds are passed through digestive system Water; coconuts Wind; puffy dandelion

Seed Development Seed coat: outer layer around seed that protects embryo and endosperm Miniature root and shoot cotyledon: storage and transfer of nutrients to embryo Dicots = dicotyledon = 2 Monocots= (mono)cotyledon Embryo grows through a few stages of mitosis and stops to be dispersed (stage that you see in fruit)

Seed Germination germination: embryo grows when conditions are favorable Soak up water split seed coat trigger metabolic changes

Adaptations and Conditions Protections for developing shoots Hooked tip Sheath covering Seedling: young plant that has just emerged from the soil Vary among species Desert plants: after heavy rainfall Harsh winters: only after long period of cold Fire: clears other growth

Asexual Reproduction vegetative reproduction: asexual reproduction Cacti; dropped shoots become new plant Strawberries and grasses send out runners Some trees send out shoots from underground stems

Different Life Cycles Annuals: complete life cycle in one year Biennials: 2 years, flower in second Perennials: multiple times per year

20.2 Plant Structure Roots fibrous root: mat of thin roots spread out below the soil surface Increased surface area grasses taproot: one large vertical root with smaller branches Starch-storing Carrots

Shoots Stems, leaves, and flowers stems: support leaves and flowers nodes: point where leaves and stems attach internodes: portions of stem between nodes Transport water and nutrients

buds: undeveloped shoots Terminal bud: tip of stem Axillary: in the angles of a leaf - branches blade: main part of the leaf Primary photosynthesis site petiole: stalk that connects leaf to stem veins: throughout leaves to carry water and nutrients Some plants have modified leaves Celery stalks are leaves; onion is underground shoot

Plant Tissues Dermal Vascular Ground Meristematic: differentiates into the others

Dermal Tissue Outer covering or “skin” Epidermis: tissue of nonwoody organs One or more layers of cells Covers and protects young parts Secretes waxy cuticle Periderm: older tissue

Vascular Tissue Transports water, mineral nutrients, and organic molecules; structure xylem: water and dissolved minerals phloem: food; made in leaves and transported to parts that don’t photosynthesize

Ground Tissue Fills the spaces between dermal and vascular Most of young nonwoody plant Photosynthesis, stoage and support cortex: ground tissue in a root

Leaf Structure

Types of Plant Cells parenchyma: thin cell walls and large central vacuoles Food storage Photosynthesis and cellular respiration Fruits Phloem collenchyma: unevenly thick cell walls Grouped in strands or cylinders Support to young parts Young stems and petioles sclerenchyma: specialized for support Die and leave behind a “skeleton” xylem

20.3 Primary Growth Plants continue to grow their entire lives meristems: tissues that differentiate into new dermal, vascular, and ground tissue apical meristems: tips of roots and buds of shoots Grow in length and branches primary growth: growth in length

Primary Growth of Roots root cap: tip of the root Protects dividing cells of apical meristem Apical meristem Replaces cells of root cap Produces cells for primary growth Forms 3 cylinders of cells; dermal, ground, vascular Cells elongate by taking up water

Primary Growth of Shoots Apical meristem: tip of terminal bud Elongation just below Auxillary buds Formed as elongating cells push upward Cylinders of cells

20.4 Secondary Growth Growth in plant width Woody plants; vines, shrubs, trees Vascular cambium and cork cambium vascular cambium: cylinder of actively diving cells between xylem and phloem Adds secondary vascular tissue to primary Accumulates as wood

Cork cambium cork cambium: meristem that develops from parenchyma cells Produces tough outer layer of cork Dead cork cells leave thick, waxy walls; protects and prevents water loss bark: everything outside vascular cambium Phloem, cork, cork cambium

Tree Rings Rings = yearly activity of vascular cambium Spring; cells are larger and thinner Cool and wet Summer: cells are smaller and thicker Hot and dry Heartwood - dead xylem Sapwood - xylem transports water