Plant Structure and Function Chapters 35-39

Evolution of Plants All Plants… multicellular, eukaryotic, autotrophic, alternation of generations

Alternation of Generations Sporophyte (diploid) produces haploid spores via meiosis Gametophyte (haploid) produce haploid gametes via mitosis Fertilization joins two gametes to form a zygote

Angiosperms Monocots vs. Dicots named for the number of cotyledons present on the embryo of the plant + monocots - orchids, corn, lilies, grasses + dicots - roses, beans, sunflowers, oaks

Plant Morphology Morphology (body form) shoot and root systems + inhabit two environments - shoot (aerial) + stems, leaves, flowers - root (subterranean) + taproot, lateral roots vascular tissues + transport materials between roots and shoots - xylem/phloem

Plant Anatomy Anatomy (internal structure) division of labor + cells differing in structure and function - parenchyma, collenchyma, sclerenchyma (below) - water- and food-conducting cells (next slide) Parenchyma St: “typical” plant cells Fu: perform most metabolic functions Collenchyma St: unevenly thickened primary walls Fu: provide support but allow growth in young parts of plants Sclerenchyma St: hardened secondary walls (LIGNIN) Fu: specialized for support; dead

Plant cell types Parenchyma cells Collenchyma cells Cell wall Sclerenchyma cells

Plant cell types Xylem Phloem Vessel Tracheids Tracheids and vessels WATER-CONDUCTING CELLS OF THE XYLEM Vessel Tracheids Tracheids and vessels element Pits SUGAR-CONDUCTING CELLS OF THE PHLOEM Companion cell Sieve-tube member Sieve-tube members: longitudinal view Sieve plate Nucleus Cytoplasm Companion cell

Water- and Food-conducting Cells Xylem (water) dead at functional maturity tracheids- tapered with pits vessel elements- regular tubes Phloem (food) alive at functional maturity sieve-tube members- arranged end to end with sieve plates & Companion cells

Plant Tissues Three Tissue Systems dermal tissue + epidermis (skin) - single layer of cells that covers entire body - waxy cuticle/root hairs vascular tissue + xylem and phloem - transport and support ground tissue + mostly parenchyma - occupies the space b/n dermal/vascular tissue - photosynthesis, storage, support

Plant Growth Meristems perpetually embryonic tissues located at regions of growth + divide to generate additional cells (initials and derivatives) - apical meristems (primary growth- length) + located at tips of roots and shoots - lateral meristems (secondary growth- girth)

Roots A root Is an organ that anchors the vascular plant Absorbs minerals and water Often stores organic nutrients Taproots found in dicots and gymnosperms Lateral roots (Branch roots off of the taproot) Fibrous root system in monocots (e.g. grass) Figure 35.3

Modified Roots Many plants have modified roots (a) Prop roots (b) Storage roots (c) “Strangling” aerial roots (d) Buttress roots (e) Pneumatophores (a) Prop roots (b) Storage roots

Primary Growth of Roots apical meristem + root cap + three overlapping zones - cell division - elongation - maturation

Stems A stem is an organ consisting of Nodes (could be opposite or alternate) Internodes

Modified Stems Stolons Storage leaves Rhizomes Stem Node Root Bulbs Tubers (c) Bulbs Stolons (a) Storage leaves Stem Root Node Rhizome

Buds An axillary bud Is a structure that has the potential to form a lateral shoot, or branch A terminal bud Is located near the shoot tip and causes elongation of a young shoot Gardening tip: Removing the terminal bud stimulates growth of axillary buds

Primary Growth in Shoots apical meristem (1, 7) + cell division occurs + produces primary meristems - protoderm (4, 8) - procambium (3, 10) - ground meristem (5, 9) axillary bud meristems + located at base of leaf primordia leaf primordium (2, 6) + gives rise to leaves

The leaf Is the main photosynthetic organ of most vascular plants Leaves generally consist of Blade Stalk Petiole

Leaf Morphology In classifying angiosperms Taxonomists may use leaf morphology as a criterion Petiole (a) Simple leaf (b) Compound leaf. (c) Doubly compound leaf. Axillary bud Leaflet

Modified Leaves Tendrils Spines Storage leaves Bracts Reproductive leaves. The leaves of some succulents produce adventitious plantlets, which fall off the leaf and take root in the soil.

Leaf Anatomy Epidermal Tissue upper/lower epidermis guard cells (stomata) Ground Tissue mesophyll +palisade/spongy parenchyma Vascular Tissue veins + xylem and phloem

Cutaway drawing of leaf tissues Leaf Anatomy Key to labels Dermal Ground Vascular Guard cells Stomatal pore Epidermal cell 50 µm Surface view of a spiderwort (Tradescantia) leaf (LM) (b) Cuticle Sclerenchyma fibers Stoma Upper epidermis Palisade mesophyll Spongy Lower Vein Xylem Phloem Bundle- sheath Cutaway drawing of leaf tissues (a) Air spaces Guard cells 100 µm Transverse section of a lilac (Syringa) leaf (LM) (c)

The Three Tissue Systems: Dermal, Vascular, and Ground

Dermal Tissue Protects plant from: Physical damage Pathogens H2O loss (Cuticle)

Vascular tissue Carries out long-distance transport of materials between roots and shoots Consists of two tissues, xylem and phloem

Ground Tissue Includes various cells specialized for functions such as storage, photosynthesis, and support Pith = ground tissue internal to the vascular tissue Cortex = ground tissue external to the vascular tissue

Secondary Growth Lateral Meristems vascular cambium + produces secondary xylem/phloem (vascular tissue) cork cambium + produces tough, thick covering (replaces epidermis) secondary growth + occurs in all gymnosperms; most dicot angiosperms

The Vascular Cambium and Secondary Vascular Tissue Is a cylinder of meristematic cells one cell thick Develops from parenchyma cells

2° Growth As a tree or woody shrub ages The older layers of secondary xylem, the heartwood, no longer transport water and minerals The outer layers, known as sapwood Still transport materials through the xylem

Cork Cambium Periderm protective coat of secondary plant body + cork cambium and dead cork cells - bark cork cambium produces cork cells

Plant Transport Chapter 36

A variety of physical processes Are involved in the different types of transport Sugars are produced by photosynthesis in the leaves. 5 Through stomata, leaves take in CO2 and expel O2. The CO2 provides carbon for photosynthesis. Some O2 produced by photosynthesis is used in cellular respiration. 4 CO2 O2 Light H2O Sugar Transpiration, the loss of water from leaves (mostly through stomata), creates a force within leaves that pulls xylem sap upward. 3 Sugars are transported as phloem sap to roots and other parts of the plant. 6 Water and minerals are transported upward from roots to shoots as xylem sap. 2 Roots exchange gases with the air spaces of soil, taking in O2 and discharging CO2. In cellular respiration, O2 supports the breakdown of sugars. 7 Roots absorb water and dissolved minerals from the soil. 1 O2 H2O CO2 Minerals

The Central Role of Proton Pumps Proton pumps in plant cells Create a hydrogen ion gradient Contribute to membrane potential CYTOPLASM EXTRACELLULAR FLUID ATP H+ Proton pump generates membrane potential and H+ gradient. – +

(Membrane potential and cation uptake Plant cells use energy stored in the proton gradient and membrane potential To drive the transport of many different cations + CYTOPLASM EXTRACELLULAR FLUID Cations ( , for example) are driven into the cell by the membrane potential. Transport protein K+ – (Membrane potential and cation uptake

Figure 37.6b Soil particle – K+ Ca2+ Mg2+ Cu2+ H+ H2CO3 HCO3– + (b) Cation exchange in soil. Hydrogen ions (H+) help make nutrients available by displacing positively charged minerals (cations such as Ca2+) that were bound tightly to the surface of negatively charged soil particles. Plants contribute H+ by secreting it from root hairs and also by cellular respiration, which releases CO2 into the soil solution, where it reacts with H2O to form carbonic acid (H2CO3). Dissociation of this acid adds H+ to the soil solution. H2O + CO2 H2CO3 HCO3– + Root hair K+ Cu2+ Ca2+ Mg2+ H+ Soil particle –

Cotransport A transport protein couples the passage of H+ to anions – NO3– NO3 – – + Cotransport of anions of through a cotransporter. Cell accumulates anions ( , for example) by coupling their transport to the inward diffusion

Contransport of a neutral solute Cotransport Is also responsible for the uptake of sucrose by plant cells H+ S Plant cells can also accumulate a neutral solute, such as sucrose ( ), by cotransporting down the steep proton gradient. – + Contransport of a neutral solute

Water potential Is a measurement that combines the effects of solute concentration and pressure Determines the direction of movement of water Water Flows from regions of high water potential to regions of low water potential

Quantitative Analysis of Water Potential The addition of solutes Reduces water potential 0.1 M solution H2O Pure water (a)

Negative pressure Decreases water potential H2O (d)

Application of physical pressure Increases water potential H2O (b) H2O (c)

Aquaporin Proteins and Water Transport Aquaporins Are transport proteins in the cell membrane that allow the passage of water Do not affect water potential

Fluid Movement Movement of fluid in the xylem & phloem is driven by pressure differences at opposite ends of the xylem vessels and sieve tubes

Water and minerals ascend from roots to shoots through the xylem Plants lose an enormous amount of water through transpiration, the loss of water vapor from leaves and other aerial parts of the plant The transpired water must be replaced by water transported up from the roots

Pushing Xylem Sap: Root Pressure At night, when transpiration is very low Root cells continue pumping mineral ions into the xylem of the vascular cylinder, lowering the water potential Water flows in from the root cortex Generating root pressure

Root pressure sometimes results in guttation

Transpiration produces negative pressure (tension) in the leaf Which exerts a pulling force on water in the xylem, pulling water into the leaf The transpirational pull on xylem sap Is transmitted all the way from the leaves to the root tips and even into the soil solution Is facilitated by cohesion and adhesion

Upper epidermal tissue The stomata of xerophytes Are concentrated on the lower leaf surface Are often located in depressions that shelter the pores from the dry wind Lower epidermal tissue Trichomes (“hairs”) Cuticle Upper epidermal tissue Stomata 100 m

Translocation through Phloem Is the transport of organic nutrients in the plant Phloem sap Is an aqueous solution that is mostly sucrose Travels from a sugar source to a sugar sink

Sugar Source & Sink A sugar source Is a plant organ that is a net producer of sugar, such as mature leaves A sugar sink Is an organ that is a net consumer or storer of sugar, such as a tuber or bulb

Transpiration Lab

Control of Transpiration Photosynthesis-Transpiration Compromise guard cells help balance plant’s need to conserve water with its requirement for photosynthesis

Stomatal closing 1. Potassium ions move out of the vacuole and out of the cells. 2. Water moves out of the vacuoles, following potassium ions. 3. The guard cells shrink in size. 4. The stoma closes. Stomatal opening Potassium ions move into the vacuoles. Water moves into the vacuoles, following potassium ions. The guard cells expand. The stoma opens.

Chapter 37 Plant nutrition

Plant Nutrition What does a plant need to survive? 9 macronutrients, 8 micronutrients + macro- required in large quantities - C, H, N, O, P, S, K, Ca, Mg + micro- required in small quantities - Fe, Cl, Cu, Mn, Zn, Mo, B, Ni + usually serve as cofactors of enzymatic reactions

The most common deficiencies Are those of nitrogen, potassium, and phosphorus Phosphate-deficient Healthy Potassium-deficient Nitrogen-deficient

Hydroponics Remove only one macronutrient to see effects on plant

Soil Texture and Composition texture depends on size of particles + sand-silt-clay - loams: equal amounts of sand, silt, clay composition + horizons - living organic matter - A horizon: topsoil, living organisms, humus - B horizon: less organic, less weathering than A horizon - C Horizon: “parent” material for upper layers soil conservation issues + fertilizers, irrigation, erosion

Soil Aeration A mixture of mineral particles, decaying organic material, living organisms, air, and water, which together support the growth of plants

Soil Bacteria and Nitrogen Availability Nitrogen-fixing bacteria convert atmospheric N2 plants absorb ammonium (NH4+), nitrate (NO3-) Atmosphere N2 Soil Nitrogen-fixing bacteria Organic material (humus) NH3 (ammonia) NH4+ (ammonium) H+ (From soil) NO3– (nitrate) Nitrifying bacteria Denitrifying bacteria Root NH4+ Nitrate and nitrogenous organic compounds exported in xylem to shoot system Ammonifying bacteria

Nutritional Adaptations Symbiotic Relationships symbiotic nitrogen fixation + Legume root nodules contain bacteroids (Rhizobium bacteria) - mutualistic relationship - Crop rotation (Legumes mycorrhizae + symbiotic associations of fungi and roots parasitic plants + plants that supplement their nutrition from host - mistletoe, dodder plant, Indian pipe carnivorous plants + supplement nutrition by digesting animals

Mycorrhizae and Plant Nutrition Are modified roots consisting of mutualistic associations of fungi and roots The fungus Benefits from a steady supply of sugar donated by the host plant In return, the fungus Increases the surface area of water uptake and mineral absorption and supplies water and minerals to the host plant

Staghorn fern, an epiphyte Mistletoe, a photosynthetic parasite Unusual nutritional adaptations in plants Staghorn fern, an epiphyte EPIPHYTES PARASITIC PLANTS CARNIVOROUS PLANTS Mistletoe, a photosynthetic parasite Dodder, a nonphotosynthetic parasite Host’s phloem Haustoria Indian pipe, a nonphotosynthetic parasite Venus’ flytrap Pitcher plants Sundews Dodder

Phytoremediation Poplars remove nitrates Mustard removes uranium

Wetlands Pesticide Levels (ppb) in Ground Water Before & After Phytoremediation Activities Wetlands

Uptake of Soil Solution Symplastic Route continuum of cytosol based on plasmodesmata Apoplastic Route continuum of cell walls and extracellular spaces Lateral transport of soil solution alternates between apoplastic and symplastic routes until it reaches the Casparian strip

Casparian Strip A belt of suberin (purple) that blocks the passage of water and dissolved minerals.

Chapter 38 Plant Reproduction

Plant Reproduction Sporophyte (diploid) produces haploid spores via meiosis Gametophyte (haploid) produce haploid gametes via mitosis Fertilization joins two gametes to form a zygote

(a) An idealized flower. An overview of angiosperm reproduction Anther at tip of stamen Filament Anther Stamen Pollen tube Germinated pollen grain (n) (male gametophyte) on stigma of carpel Ovary (base of carpel) Ovule Embryo sac (n) (female gametophyte) FERTILIZATION Egg (n) Sperm (n) Petal Receptacle Sepal Style Ovary Key Haploid (n) Diploid (2n) (a) An idealized flower. (b) Simplified angiosperm life cycle. See Figure 30.10 for a more detailed version of the life cycle, including meiosis. Mature sporophyte plant (2n) with flowers Seed (develops from ovule) Zygote (2n) Embryo (2n) (sporophyte) Simple fruit (develops from ovary) Germinating seed Carpel Stigma

Mechanisms That Prevent Self-Fertilization Stigma Stigma Pin flower Thrum flower Anther with pollen The most common anti-selfing mechanism in flowering plants Is known as self-incompatibility, the ability of a plant to reject its own pollen

Preventative Selfing Some plants Recognition of self pollen Reject pollen that has an S-gene matching an allele in the stigma cells Recognition of self pollen Triggers a signal transduction pathway leading to a block in growth of a pollen tube

Double Fertilization Double Fertilization pollen grain lands on stigma + pollen tube toward ovule + both sperm discharged down the tube - egg and one of the sperm produce zygote - 2 polar nuclei and sperm cell produce endosperm + ovule becomes the seed coat + ovary becomes the fruit

Seed Structure and Development

The radicle In many eudicots Is the first organ to emerge from the germinating seed In many eudicots A hook forms in the hypocotyl, and growth pushes the hook above ground Foliage leaves Cotyledon Hypocotyl Radicle Epicotyl Seed coat

Monocots The coleoptile Use a different method for breaking ground when they germinate The coleoptile Pushes upward through the soil and into the air Foliage leaves Coleoptile Radicle

Plant Responses to Internal and External Signals Chapter 39 Plant Responses to Internal and External Signals

Tropisms Growth toward or away from a stimulus Gravitropism (Gravity) Phototropism (Light) Thigmotropism (Touch)

Etiolation The stems of plants raised in the dark elongate much more rapidly than normal, a phenomenon called etiolation.

Signal Transduction Pathway Figure 39.3 CELL WALL CYTOPLASM   1 Reception 2 Transduction 3 Response Receptor Relay molecules Activation of cellular responses Hormone or environmental stimulus Plasma membrane

Plant hormones help coordinate growth, development, and responses to stimuli Are chemical signals that coordinate the different parts of an organism

Photoperiod, the relative lengths of night and day + Is the environmental stimulus plants use most often to detect the time of year