Plants, Tissues and Nutrition Plant types and their evolution • Terrestrial plants evolved from aquatic green algae • There are three main types: • Bryophytes- mosses and hornwarts • Ferns, Lycophytes and horsetails • Gymnosperms and angiosperms Fig. 15-1, p.245 charophytes flowering bryophytes lycophytes horsetails ferns cycads ginkgos conifers gnetophytes plants seed plants plants with true leaves vascular plants land plants (closely related groups) Fig. 15-4, p.246 zygote only, no sporophyte green algae bryophytes ferns gymnosperms angiosperms Fig. 15-3, p.246 Bryophytes • Mosses and Hornwarts – “Leaves” have a cuticle to conserve water – A rudimentary root system anchors them to substratum and allows for absorption – Need to live in moist environment – Produce spores and free swimming sperm, need water – Most can survive drying out by going dormant Ferns Lycophytes and Horsetails • Share features with bryophytes • Have rudimentary roots • Have vascular system Carboniferous Lycophytes •Some formed vast forests •Source of our modern “fossil fuels” •Extinct except for a few groups Lepidodendron Fig. 15-7a, p.249 Ferns and Horsetails • Have “true leaves” • Root system vegetative stem • Still need moisture • Produce spores (swimming sperm) strobilus on fertile stem Fig. 15-8c, p.249 Seed Producing plants: Gymnosperms Gymnosperms Have all adaptations for living on land: Produce seeds Have a vascular system Well developed roots “true leaves” conserve water and exchange gases with atmosphere Angiosperms (Flowering Plants) • Flowers – Ovules and (after fertilization) seeds develop in ovary petal stamen (microspores form here) sepal ovule carpel in an (megaspores ovary form here) Fig. 15-14, p.254 Flowering Plants • Have all the same land adaptations as gymnosperms plus flowers • Dominate the plant kingdom • Magnoliids, eudicots and monocots Monocots and Eudicots • Two major plant groups • Same tissues, but arranged in different ways • Eudicots are the more diverse group Monocots and Eudicots • Differ in – Cotyledon number – Leaf venation – Floral parts – Pollen structure – Arrangement of vascular bundles in stem a Eudicots b Monocots Inside seeds, two cotyledons Inside seeds, one cotyledon (seed leaves of embryo) (seed leaf of embryo) Usually four or five floral Usually three floral parts parts (or multiples of (or multiples of threes) four or five) Leaf veins usually Leaf veins usually running in a netlike array parallel with one another Three pores and/or One pore or furrow in furrows in the pollen grain the pollen grain surface surface Vascular bundles organized Vascular bundles distributed as a ring in ground tissue throughout ground tissue Fig. 18-4, p.303 Plant Body Plan • Plant body plan is DERMAL TISSUES divided into VASCULAR TISSUES • Shoots • Roots GROUND TISSUES SHOOT SYSTEM ROOT SYSTEM Body Plan • Ground tissue system- support • Vascular tissue system- transport • Dermal tissue system- conserve water Plant organ and tissue systems • Shoots – Produce food by photosynthesis – Carry out reproductive functions • Roots – Anchor the plant – Penetrate the soil and absorb water and dissolved minerals – Store food shoot tip (terminal bud) activity at meristems primary tissues form as new cells lengthen, differentiate primary tissues form as new cells lengthen, activity at differentiate meristems root tip Fig. 29-3a, p.494 Meristems • Regions where cell divisions produce plant growth • Apical meristems – Lengthen stems and roots – Responsible for primary growth • Lateral meristems – Increase width of stems – Responsible for secondary growth Simple Tissues • Made up of one type of cell – Parenchyma – alive • Found in soft photosynthetic tissues – Collenchyma – alive • Provides support – Sclerenchyma – dead at maturity • Provides even more support Simple Tissues collenchyma parenchyma lignified secondary wall celery Flax fibers Pear fruit Complex Tissues Composed of mixed cell types Xylem Phloem Epidermis Vascular Tissues Xylem Phloem • Conducts water and • Transports sugars dissolved minerals • Main conducting • Conducting cells are cells are sieve-tube dead and hollow at members maturity • Companion cells assist in the loading of sugars one sieve plate cell’s Tissues in of sieve wall tube cell a Stem pit in wall companion cell a b c vessel of fibers of xylem sclerenchyma parenchyma phloem Epidermis • Covers and protects plant surfaces • Secretes a waxy, waterproof cuticle • Contains stomata • In woody plants, periderm replaces epidermis Primary Shoot Structure • Eudicot and monocot stems petiole axillary bud blade node sheath blade stem node Internal Structure of a Eudicot Stem • Outermost layer is epidermis • Cortex lies beneath epidermis • Ring of vascular bundles separates the cortex from the pith • The pith lies in the center of the stem xylem cell epidermis cortex vascular bundle pith companion cell in sieve tube phloem in phloem Fig. 18-5a, p.304 Internal Structure of • The vascular bundles a Monocot are distributed throughout the ground Stem tissue • No division of ground tissue into cortex and pith collenchyma air vessel sheath space in xylem epidermis vascular bundle pith sieve tube companion in phloem cell in phloem Fig. 18-5b, p.304 Adapted to Photosynthesis • Leaves are usually thin – High surface area-to-volume ratio – Promotes diffusion of carbon dioxide in, oxygen out • Leaves are arranged to capture sunlight – Are held perpendicular to rays of sun – Arranged so they don’t shade one another Leaf Structure UPPER cuticle EPIDERMIS PALISADE MESOPHYLL phloem SPONGY MESOPHYLL xylem LOWER EPIDERMIS CO one stoma O2 2 Leaf Veins: Vascular Bundles • Xylem and phloem; often strengthened with fibers • In eudicots, veins are netlike • In monocots, they are parallel p.305 Leaf Epidermis • Covers every leaf surface • Specialized cells Stem Growth and Development • Cells at tip of apical meristem divide • Their descendents divide and differentiate, giving rise to specialized tissues • Lateral buds are undeveloped meristematic tissue that gives rise to stems, leaves, and flowers immature leaf Stem shoot apical meristem Development procambium protoderm procambium ground meristem epidermis cortex primary phloem procambium primary xylem pith Roots Structure • Taproot system – eudicots • Fibrous root system – monocots Root Systems fibrous root system taproot system of of a grass plant a California poppy Root Structure • Root cap covers tip • Apical meristem produces the cap – Cell divisions at the apical meristem cause the root to lengthen – Farther up, cells differentiate and mature • Root Hairs- – Provide large surface area for water and mineral absorption Internal Structure of a Root • Outermost layer is epidermis • Root cortex is beneath the epidermis • Vascular cylinder contains xylem and phloem • Endodermis, then pericycle surround the vascular cylinder • In some plants, there is a central pith VASCULAR CYLINDER endodermis pericycle xylem phloem cortex epidermis root hair Vessel members are mature; root hairs are about to form. New root cells lengthen, sieve tubes mature, vessel members start forming. Most cells have stopped dividing Meristem cells are dividing fast. root tip No cell division is occurring here. root cap Fig. 18-10a, p.307 epidermis root cortex root cortex endodermis pericycle primary xylem primary phloem b Vascular cylinder, cross section Fig. 18-10b, p.307 Secondary Growth • Woody plants • A ring of vascular cambium produces secondary xylem and phloem • Wood is the accumulation of these secondary tissues, especially xylem Secondary Growth Ongoing cell divisions enlarge the inner core of secondary xylem and displace vascular cambium toward the stem. VASCULAR CAMBIUM stem surface primary xylem primary phloem VASCULAR CAMBIUM secondary xylem secondary phloem Fig. 18-11b, p.308 outer surface of stem root division division One of the One of the One of the cells two daughter two daughter vascular cells cells cambium at differentiates differentiates the start of into a xylem into a phloem secondary cell (coded cell (coded growth. blue), and the pink), and the The same pattern of cell other remains other remains division and differentiation meristatic. meristatic. into xylem and phloem cells continues through the growing season. Fig. 18-11c, p.308 Formation of Bark • All tissues outside vascular cambium • Periderm – Cork – New parenchyma – Cork cambium • Secondary phloem Woody Stem secondary HEARTWOOD SAPWOOD periderm phloem BARK vascular cambium Tree Rings • Form as a result of xylem tubes with different diameters – Wide tubes develop during wet season – Narrow tubes develop during dry season – Different diameters create discernable pattern of year’s growth vessel in xylem direction of growth early wood late wood early wood Fig. 18-12b, p.309 Tree Rings cork 2° phloem vascular cambium Annual Growth Ring 2° xylem Late wood 1° xylem Early wood Pith Woods a. Pine b. Oak c. Elm Fig. 18-13b, p.309 Plant Nutrition, Transport and Gas Exchange Soil • Minerals mixed with humus – Minerals come from weathering of rock – Humus is decomposing organic material • Composition of soil varies • Suitability for plant growth depends largely on proportions of soil particles Macronutrients Mineral elements that are required in amounts above 0.5% of the plant’s dry weight Carbon Nitrogen Magnesium Hydrogen Potassium Phosphorus Oxygen Calcium Sulfur Micronutrients Elements that are required in trace amounts for normal plant growth Chlorine Zinc Iron Copper Boron Molybdenum Manganese Leaching • Removal of nutrients from soil by water