Transcript Xylem
Ch. 35 Warm-Up 1. What are 3 ways that plant cells differ from animal cells? Most H2O and minerals taken up from the soil by a plant are absorbed by _______. 3. The main photosynthetic organs of a plant are the __________. 2. Chapter 35 Plant Structure, Growth, and Development What you must know The function of xylem and phloem tissue. The anatomy of a leaf The anatomy of a root Introduction to Plants Kingdom: Plantae Cell wall Autotroph (photosynthesis) Multicellular Angiosperms (flowering plants) ~90% plants Produce seeds within a fruit Key adaptations: flowers & fruits Plant Organization Organs • Roots • Stems • Leaves Tissues • Dermal • Vascular • Ground Cell Types • Xylem • Phloem • Parenchyma I. Plant Organs Shoot system •Above ground •Stems, leaves Root system •Underground (usually) •Roots A. Roots Anchors plant, absorbs H2O & minerals, stores sugars/starches Root hairs – tiny extensions of epidermal cells, increase surface area for H2O and mineral absorption Mycorrhizae: fungus + plant root symbiotic relationship Root hairs Fibrous Roots Mat of thin roots spread just below surface Shallow Increased surface area Fibrous Root (scallion) Taproots One thick, vertical root Many lateral (branch) roots Firmly anchors Stores food Taproot (carrot) Modified Roots Mangrove Forest in Florida B. Stems Function: display leaves Terminal bud: growth concentrated at top end of stem Secretes hormone to prevent growth of axillary buds; growth directed upward, toward light Axillary buds – located in V between leaf and stem; forms branches (lateral shoots) Pinching/pruning – removing terminal bud Modified stems Runner or stolin ◦ Aspen, strawberries, grass ◦ Grow on surface ◦ For asexual reproduction Rhizome ◦ ◦ ◦ ◦ Iris, ginger, potato, onion Grow underground Store food & DNA for new plant Tuber: end of rhizome Bulb – underground shoot ◦ Onion ◦ storage leaves C. Leaves Function: Photosynthetic organ blade petiole Modified leaves II. Plant Tissues A. Dermal Tissue Single layer, closely packed cells that cover entire plant Protect against water loss & invasion by pathogens (viruses, bacteria) Cuticle: waxy layer B. Vascular Tissue Continuous throughout plant Transports materials between roots & shoots ◦ Xylem & Phloem C. Ground Tissue Anything that isn’t dermal or vascular Function: storage, photosynthesis, support Pith: inside vascular tissue Cortex: outside vascular tissue III. Cell Types Xylem Conducts H2O and minerals up from root Dead, tubular, elongated cells B. Phloem Conducts sugar & organic compounds from leaves to other parts of plant Living cells aid movement of sugar 2 Cell Types: sieve tubes, companion cells A. Xylem Phloem Plant Growth Types of Flowering Plants: Annuals – 1 year life cycle Biennials – 2 years Perennials – continuous life cycle for many years Meristem: perpetually embryonic tissues ◦ Cells divide for plant growth Apical meristem: growth at tips of roots & buds of shoots; cause primary growth (increase length) Lateral meristem: growth thickens shoots and roots; secondary growth Primary and Secondary Growth Root Anatomy Root Hairs Zone of Maturation: primary growth becomes functionally mature Zone of Elongation: cells elongate; push root tip ahead Zone of Cell Division: apical meristem; new cells produced (mitosis) Root cap: protects meristem as it pushes through soil Leaf Anatomy ◦ Epidermis of underside interrupted by stomata (pores), flanked by guard cells (open/close stomata) ◦ Mesophyll: ground tissue between upper/lower epidermis ◦ Parenchyma: sites of photosynthesis Secondary Growth = increase diameter Involves lateral meristems ◦ Vascular cambium: produces secondary xylem (wood) ◦ Cork cambium: produces tough covering that replaces epidermis Bark = all tissues outside vascular cambium Secondary phloem Vascular cambium Secondary Late wood Early wood xylem Primary and secondary growth in a two-year-old stem Cork cambium Periderm Cork Epidermis Cortex Primary phloem Vascular cambium Primary xylem Pith Pith Primary xylem Vascular cambium Primary phloem Cortex Phloem ray Xylem ray Secondary xylem Primary xylem Cork Pith Secondary xylem (two years of production) Vascular cambium Secondary phloem Bark Most recent cork cambium Cork 0.5 mm Primary and Secondary Growth of a Stem Periderm (mainly cork cambia and cork) Vascular cambium Bark 0.5 mm Primary xylem Secondary xylem Vascular cambium Secondary phloem Primary phloem First cork cambium Primary phloem Secondary phloem Xylem ray Epidermis Transverse section of a three-yearold Tilia (linden) stem (LM) Layers of periderm Chapter 38 Angiosperm Reproduction Angiosperms have 3 unique Features: 1. 2. 3. Flowers Fruits Double Fertilization (by 2 sperm) REPRODUCTIVE VARIATIONS Pollination: transfer pollen from anther to stigma Some plants are self-pollinated Cross-pollinated plants: ◦ Self-incompatibility: plant rejects own pollen or closely related plant ◦ Maximize genetic variation Stigma Stigma Anther with pollen Pin flower Thrum flower “Pin” and “thrum” flower types reduce self-fertilization The development of a plant embryo Fruit Egg cell plant embryo Ovules inside ovary seeds Ripe ovary fruit Fruit protects enclosed seed(s) Aids in dispersal by water, wind, or animals Types of Fruit Seeds Mature seed dormancy (resting) ◦ Low metabolic rate ◦ Growth & development suspended ◦ Resumes growth when environmental conditions suitable for germination Germination Seed take up water (imbibition) trigger metabolic changes to begin growth ◦ Root develops shoot emerges leaves expand & turn green (photosynthesis) Very hazardous for plants due to vulnerability Predators, parasites, wind Plant Reproduction Sexual Asexual (Vegetative Reproduction) Flower Seeds Runners, bulbs, grafts, cuttings vegetative (grass), fragmentation, test-tube cloning Genetic diversity Clones More complex & hazardous for seedlings Simpler (no pollinator needed) Advantage in unstable environments Suited for stable environments Asexual reproduction in aspen trees Test-tube cloning of carrots Humans Modify Crops Artificial selection of plants for breeding Plant Biotechnology: ◦ Genetically modified organisms “Golden Rice”: engineered to produce betacarotene (Vit. A) Bt corn: transgenic – expresses Bt (bacteria) gene produces protein toxic to insects ◦ Biofuels – reduce CO2 emissions Biodiesel: vegetable oils Bioethanol: convert cellulose into ethanol