 24.1 The Plant Body is Organized and Constructed in a Distinctive Way Plants are stationary (sessile) Stems, leaves, and roots have structural adaptations that enable plants anchored to one spot to capture scarce resources effectively, both above and below ground Ability to grow throughout lifetime enables plants to respond to environmental cues by redirecting their growth to exploit environmental opportunities, a when roots grow toward a water supply Plant organs organized into two systems Root system Anchors plant, absorbs water and dissolved minerals, and stores the products of photosynthesis Shoot system, consists of stems, leaves, and flowers Leaves chief organ of photosynthesis Arise from nodes on stem, and between the nodes is called phytomer Stems hold and display leaves to sun and provide connections for transport of materials between roots and leaves Flowers are reproductive organs Angiosperms categorized into two clades: Monocots and Dicots Four processes that govern the development of all organisms are: Determination: the commitment of an embryonic cell to its ultimate fate in organism Differentiation: the specialization of a cell Morphogenesis: the organization and spatial distribution of cells into tissues and organs Growth: increase in body size In plants, these processes influenced by apical meristems, cells walls, and totipotency of most cells- Apical meristems: “always embryonic” and produces new roots, stems, leaves and flowers throughout plant's lifetime- Cells walls: Rigid extracellular matrix that makes it impossible for cells to move place to place- Plant morphogenesis occurs which changes direction in which tissue grows - Plant cytokinesis occurs along cell plate- Location of plant cell plate is determined as early as mitotic prophase- Totipotency: All cells in plants, even differentiated cells, are pluripotent (can readily repair damage caused by environment or herbivores)Two patterns of plant embryo formationApical-basal axis: arrangement of cells and tissues along he main axis from root to shoot Radial axis: concentric arrangement of tissue systems Formation of plant embryo Mitotic division of zygote, gives rise to 2 daughter cells Apical(upper) daughter cells produces embryo proper, other produces supporting structure called the suspensor In dicots cotyledon begins to grow(between cotyledons are shoot apical meristem and root apical meristem) Plant tissues: dermal, vascular, and ground Dermal tissue system Epidermis (outer covering of plant). Usually consists of single layerEpidermal cells can differentiate to form:-Stomata: pores for gas exchange in leaves-Trichomes (leaf hairs): provide protection against insects and damaging solar radiation- Roots hairs: increase root surface area, providing more surface for uptake of water and mineral nutrients  Cuticle, made of cutin (polymer composed of long chains of fatty acids) Limits water loss, reflects solar radiation, ad serves as barrier against pathogens  Stems and roots of woody plants develop dermal tissue called periderm Forms cork, layer impermeable to water and gases Ground Tissue System(most of plant body) 3 cells types: Parenchyma: most abundant ground tissue cells large vacuoles and ting cell walls perform photosynthesis (in shoot) and store protein (in fruits) and starch (in roots) Collenchyma: elongated cells that have thick cell walls provide support for growing tissues such as stems Schlerenchyma: cells have thick walls reinforced with polypherol polymer lignin most cells undergo programmed cell death (apoptosis), but strong cells walls provide support two types of schlerenchma cells: fibers and sclereids elongated fibers provide rigid support to parts of plants, organized into bundles Sclereids occur in various shapes and may pack together densely isolated clumps of sclereid, called stone cells, give pears and other fruits gritty texture Vascular Tissue System Xylem: distributes water and mineral ions taken up by roots to all cells of roots, stems, and leaves  Made up of dead cells - Contains two type of conducting cells- Tracheids: spindle-shaped cells, w/ thinner regions in cell wall called pits through which water can move with little resistance from one tracheid to its neighbors- Vessel elements: larger in diameter than tracheids- meet end-to-end and partially break down their end walls, forming open pipeline for water conduction Phloem: consists of living cells transport carbohydrates (primarily sugars) from sites produced by photosynthesis to sites where they are used or stored characteristic cell is sieve tube elements, which meet end-to-end, forming sieve tubes connected by plasmodesmata, which form set of pores called sieve plate 24.2 Meristems, Build Roots, Stems, and Leaves All plants experience primary growth, lengthening of roots and shoots by proliferation of new roots and shoots through branching Secondary growth, increase in thickness Plant that results entirely from primary growth consists of nonwoody issues and is referred to asherbaceous Two types of meristems contribute to growth and development: Apical meristems: orchestrate primary growth, giving rise to primary plant body. Growth characterized by cell division followed by cell expansion Lateral meristems: orchestrate secondary growth Two lateral mersitems, vascular cambium and cork cambium Growth of shoot or root is indeterminate  Division → Expansion → Differentiation Three primary meristems protoderm, ground meristem, procambium These meristems give rise to 3 tissue systems Protoderm → Dermal tissue  Ground meristem → Ground tissue system Procambrium → Vascular tissue system Root apical meristem gives rise to root cap and three primary meristems Root cap: protects delicate growing region of root as it pushes through soil cells of root cap often damaged and replaced constantly detects pull of gravity and controls downward growth of roots Apical and primary meristems constitute zone of cell division Zone of elongation: newly formed cells elongating and pushing root farther into soil Zone of cell maturation: cells differentiating Products of three primary meristems are tissue systems of mature root (epidermis, cortex, stele) Protoderm gives rise to epidermis, outer