Ch. 35 Warm-Up 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 _______. The main photosynthetic organs of a plant are the __________.

Plant Structure, Growth, and Development 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 Tissues Cell Types Roots Stems Leaves Dermal Vascular Ground Cell Types Xylem Phloem Parenchyma

I. Plant Organs Above ground Stems, leaves Underground (usually) Roots Shoot system Underground (usually) Roots Root system

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 Taproots Mat of thin roots spread just below surface Shallow Increased surface area One thick, vertical root Many lateral (branch) roots Firmly anchors Stores food Taproot (carrot) Fibrous Root (scallion)

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 Rhizome Bulb – underground shoot 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 petiole blade

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 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

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

Primary Growth of a Root Cortex Vascular cylinder Epidermis Key Zone of maturation Root hair Dermal Ground Vascular Zone of elongation Apical meristem Zone of cell division Root cap 100 µm

Primary Growth of Shoots Shoot apical meristem: dome of dividing cells at tip of terminal bud; divide and elongate

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

Primary and Secondary Growth of a Stem in a two-year-old stem Secondary phloem Vascular cambium Cork cambium Secondary xylem Late wood Early wood Periderm Cork Epidermis Cortex Pith Primary phloem Primary xylem Vascular cambium Transverse section of a three-year- old Tilia (linden) stem (LM) Vascular cambium Primary phloem Cortex Epidermis Xylem ray Primary xylem Bark Phloem ray Growth Pith Xylem ray 0.5 mm 0.5 mm Primary xylem Primary and Secondary Growth of a Stem Secondary xylem Vascular cambium Secondary phloem Primary phloem First cork cambium Cork Periderm (mainly cork cambia and cork) Growth Primary phloem Secondary phloem Secondary xylem (two years of production) Vascular cambium Secondary xylem Vascular cambium Secondary phloem Primary xylem Bark Most recent cork cambium Pith Layers of periderm Cork

Angiosperm Reproduction Chapter 38 Angiosperm Reproduction

Angiosperms have 3 unique Features: Flowers Fruits Double Fertilization (by 2 sperm)

REPRODUCTIVE VARIATIONS

Pollination: transfer pollen from anther to stigma

“Pin” and “thrum” flower types reduce self-fertilization Some plants are self-pollinated Cross-pollinated plants: Self-incompatibility: plant rejects own pollen or closely related plant Maximize genetic variation Stigma Pin flower Anther with pollen 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

(Vegetative Reproduction) 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 beta-carotene (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