Plant Anatomy and Nutrient Transport

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Plant Anatomy and Nutrient TransportChapter 43 In order to survive, plants have toThe best ways to appreciate plants is to consider how they overcome the challenges encountered by life on Earth

Obtain energy Obtain water and other nutrients Distribute water and nutrients through the body Exchange gases Support the body Grow and develop Reproduce

Evolution has produced a variety of different types of plants Plant body Organization Two major parts The root system of a plant The shoot systemRoot SystemsBranched portions of the plant body Embedded in the soilSix functions -Anchor the plant Absorb water and minerals from soil Store surplus food, carbohydrates manufactured in the shootTransport water, minerals, sugars, hormones to and from shoot Produce hormones Interact with soil fungi and bacteria that help provide nutrients to the plant The Shoot The shoot system is buds, leaves, flowers, fruits - all on parts of stems Buds give rise to leaves or flowers Leaves - sites of photosynthesis Flowers - reproductive organs, producing male and female gametes, then help them to reach one another Flowers produce seeds enclosed within fruits (protect and aid in dispersal)Stems - branched, elevate the leaves, flowers, fruitElevating the fruit helps disperse the seeds Some parts are specialized to transport water, minerals, food molecules, others produce hormones Two groups of flowering plants Monocots - lilies, daffodils, tulips, palm trees, grasses lawn grasses, and wheat, rice, corn, oats, bamboo

Dicots - broad-leafed plants, including deciduous trees, bushes, vegetables, and flowers in fields and gardens

There are differences between monocots and dicots, but the characteristic that gives these groups their name is the number of cotyledons

The part of a plant embryo that absorbs and stores food reserves in the seed, then transfers the food to the rest to the embryo when the seed sprouts

Monocots have a single cotyledon Dicots have two cotyledons

structuresleaf primordiaapical meristemleafterminal bud branch rootslateral bud flowerstembranchfruitbladepetiolenoderoot hairsroot capenergy acquisitionby photosynthesis;gas exchangereproductionbody support;transport of waterand nutrientsAcquisitionof water andmineralsreproductiongrowth anddevelopment ofplant structuresfunctionsrootshoot systemroot systemThe Structures and Functions of a Flowering Plant Characteristics of Monocots and Dicots

FlowersLeavesRootsSeedsStemscotyledonembryocotyledonsembryoFlower parts are inthrees or multiplesof threeFlower parts are infours or fives or multiplesof four or fiveLeaves have smooth edges,often narrow, with parallel veinsLeaves are palmate (handlike)or oval with netlike veinsVascular bundlesare scatteredthroughout the stemMonocots have afibrous root systemThe seed has onecotyledon (seed leaf)The seed hastwo cotyledons(seed leaves)Dicots have ataproot systemVascular bundlesare arranged in aring around the stemDicotsMonocotsPlant Development Dramatically different from animalsOne difference - timing and distribution of growth

In animals, the proportions of a newborn differs from an adult, parts of a newborns body grow until they reach adult size and structure, then growth stops

Flowering plants grow throughout their lives, never reaching a stable adult body form

Most plants grow longer or taller only at the tips of their branches and roots A swing tied to a tree branch or initials carved in tree bark do not move farther up from the ground as the tree grows

Plants are composed of two types of cellsDuring plant growth, meristem cells give rise to differentiated cells

Meristem cells, like animal stem cells, are unspecialized and capable of mitotic cell division Some daughter cells lose the ability to divide and become differentiated cells, with specialized structures and functions Continued division of meristem cells keep the plant growing throughout its lifeDifferentiated daughter cells form the non-growing parts of the plant, as leaves -10Where Growth OccursPlants grow as a result of cell division and differentiation of meristem cells found in two general locations

Apical meristems - located at the tips of roots and shoots Growth produced by apical meristem cells is primary growthIncrease in the height or length of a shoot or root, development of specialized parts of the plant - leaves and buds Lateral meristems (side meristems, cambium) - concentric cylinders of meristem cells

Animation: Primary Growth

Secondary Growth Division of lateral meristem cells and differentiation of their daughter cells produce further concentric cylinders of secondary growth, an increase in the diameter and strength of roots and shoots Occurs in woody plants - deciduous trees, shrubs, conifers Some woody plants become very tall and thick and may live hundreds to thousands of years

Many plants do not undergo secondary growth Plants that lack secondary growth are soft bodied, with flexible, fairly short stems These herbaceous, typically short-lived plants include lettuce, beans, lilies, and grasses

Tissues and Cell Types? As meristem cells differentiate, they produce a variety of cell types One or more specialized types of cells work together to perform a specific function, as conducting water and minerals = tissue Functional groups of more than one tissue = tissue systems Dermal tissue system covers the outer surface of the plant Ground tissue system makes up the body of young plants; its functions include photosynthesis, storage, and support Vascular tissue system transports fluids throughout the plant bodyTissues and Cell Types

Dermal TissuesDermal tissue system covers the plant body Two types of dermal tissues: epidermal tissue periderm Epidermal Tissues Epidermal tissue forms the epidermis - outermost cell layer covering the leaves, stems, and roots of all young plants, also covers flowers, seeds, and fruit In herbaceous plants, it forms the outer covering of the entire plant body throughout its life Above ground - generally composed of tightly packed, thin-walled cells, covered with waterproof, waxy cuticle secreted by the epidermal cells The cuticle reduces the evaporation of water from the plant and helps protect it from the invasion of disease microorganisms Adjustable pores regulate the movement of water vapor, O2, and CO2 across the epidermis of leaves and young stems In contrast, the epidermal cells of roots are not covered with cuticle that would prevent them from absorbing water and minerals

PeridermReplaces epidermal tissue on the roots and stems of woody plants as they age

Composed of multiple layers of cork cells on the outside of the root or stem and a layer of lateral meristem tissue - cork cambium - that generates the cells Cork cells produce thick, waterproof cell walls as they grow, then die as they reach maturity Because of multiple layers of waterproof cork cells on their surface, root segments that are covered with periderm help anchor the plant in the soil, but can not absorb water and minerals

Ground Tissue Compromises most of the young plant body

All of the tissue of the plant body except dermal and vascular tissues

Three types of ground tissues are parenchyma, collenchyma, and sclerenchyma Parenchyma Parenchyma - most abundant - makes up most of young plant body The cells - called parenchyma cells - have thin cell walls and are alive at maturity They carry out the plants metabolic activities, photosynthesis , secretion of hormones, food storage Potatoes, seeds, fruits, storage roots are packed with parenchyma cells that store sugars and starches Help to support the bodies of many plants, especially herbaceous plantsSome cells can divide In addition to making up much of the ground tissue system, parenchyma cells are found in periderm and vascular tissues

Parenchyma

(a) Parenchyma cells in a white potatothin cell wall stored starchCollenchyma Cells that are elongated, with thickened but flexible cell walls Alive at maturity, generally cannot divide Collenchyma tissue provides support for entire body of young and non-woody plants, the leaf stalks, or petioles, of all plants Celery stalks are thick petioles, are supported by strings composed of collenchyma cells

(b) Collenchyma cells in a celery stalkthick cell wallCollenenchyma Sclerenchyma Composed of cells with thick, hardened cell walls Sclerenchyma cells support and strengthen the plant body; they die after they differentiate Their thick cell walls then remain as a source of support Sclerenchyma cells form nut shells and the outer covering of peach pits Scattered throughout the parenchyma cells in a pear, sclerenchyma cells give pears their gritty texture Sclerenchyma cells support vascular tissues and form an important component of wood

(c) Sclerenchyma cells in a pearthick cell wallSclerenenchyma Transports water and nutrients Conducts water and dissolved substances throughout the body Consists of two conducting tissues: xylem and phloem The Vascular Tissue SystemXylem Transports water and dissolved minerals from the roots to the rest of the plant, only in one direction.

In angiosperms, xylem contains supporting sclerenchyma fibers and two specialized conducting cell types: tracheids and vessel elements Both tracheids and vessel elements develop thick cell walls, then die as their final step of differentiation, leaving hollow tubes of nonliving cells wall Xylem Tissues Tracheids - thin, elongated cells stacked atop one another Tapered, overlapping cells resemble the tips of hypodermic needles The ends and sides of tracheids contain pits - porous dimples in the walls that separate adjacent cells Because the cell wall in a pit is both thin and porous, water and minerals pass freely fr