C35 | Plant Structure and Growth

Are Plants Computers?

(True) - Plants such as romanesco, grow according to a genetically determined, repetitive program.

Plant Development - It is also dependent on environmental conditions, much more so than animals.

(True) - Growth in response to environmental change facilitates resource acquisition in plants.

Concept 35.1: Plants Have a Hierarchical Organization Consisting of Organs, Tissues, and Cells.

(True) - Plants have organs composed of different tissues, which in turn are composed of different cell types.

Cell - It is the fundamental unit of life.

Tissue - A group of cells consisting of one or more cell types that together perform a specialized function.

Organ - Consists of several types of tissues that together carry out particular functions.

Basic Vascular Plant Organs: Roots, Stems, and Leaves

Morphology - Basic ___ of vascular plants reflects their evolution as organisms that draw nutrients from below ground and above ground.

Water and Minerals - What do plants take up below ground?

CO2 and Light - What do plants take up above ground?

Roots, Stems, Leaves - Three basic organs evolved to facilitate efficient resource acquisition.

Root System & Shoot System - Plant organs are organized into two systems, which are?

Roots - What relies on sugar produced by photosynthesis in the shoot system?

Shoots - What relies on water and minerals absorbed by the root system?

Roots

Root - An organ that anchors the plant, absorbs minerals and water, and stores carbohydrates.

Primary Root - What is the first emerging root?

Lateral Roots - The primary root branches to form , which improve anchorage and water absorption.

Taproot System - Tall plants with large shoot masses generally have a _ System.

Taproot - This generally develops from the primary root and functions in anchoring the plant in the soil.

Fibrous Root System - Small or trailing plants generally have this root system that spreads out like a thick mat below the soil surface.

(True) - In the fibrous root system, the primary root dies early on and does not form a taproot.

Adventitious Roots - These roots arise from the stem and give rise to many branching lateral roots.

(True) - In most plants, absorption of water and minerals occurs primarily near the tips of roots.

(True) - Absorption primarily occurs in the tips of the lateral roots.

Root Hairs - Finger-like extensions of epidermal cells, form near the root tip and increase the absorptive surface of the root.

Mycorrhizal Associations - Most root systems form ___ Associates.

(True) - Many plants have root adaptations with specialized functions.

Stems

Stem - A plant organ consisting of an alternating system of nodes and internodes.

Nodes - Points at which leaves are attached.

Internodes - The stem segments between nodes.

Apical Bud - The growing tip that causes elongation of a young shoot.

Axillary Bud - A structure that has the potential to form a lateral branch, thorn, or flower.

Stem - Its primary function is to elongate and orient the shoot to maximize photosynthesis.

(True) - Many plants have modified stems that perform alternate functions (eg. rhizomes, stolons, tubers).

Leaves

Leaf - It is the main photosynthetic organ of most vascular plants. They intercept light, exchange gases, dissipate heat, and defend the plant from herbivores and pathogens.

(True) - Leaves generally consist of a flattened blade and a petiole.

Blade & Petiole - What generally comprises leaves?

Petiole - A stalk that joins the leaf to a node of the stem.

(True) - Monocots and eudicots differ in the arrangement of veins.

Veins - It is vascular tissue of leaves.

Monocots - Parallel veins in leaves = ?

Eudicots - Branching veins in leaves = ?

Mainly Floral Morphology, sometimes a variation in Leaf Morphology - What do taxonomists rely on as a criterion for identifying angiosperms.

(True) - A leaf shape may be simple or compound.

(True) Some plant species have evolved modified leaves that serve various functions.

Dermal, Vascular, and Ground Tissues

Dermal, Vascular, Ground - Three tissue types that compose roots, stems, and leaves.

(True) - Each of the three tissue types forms a tissue system, which is continuous throughout the plant.

Dermal Tissue Systems

Epidermis - In nonwoody plants, the dermal tissue system consists of the?

Cuticle - A waxy coating that helps prevent water loss from the epidermis.

Periderm - In woody plants, these protective tissues replace the epidermis, especially in the older regions of the stems and roots. They are thicker and stronger than the epidermis.

Guard Cells - These are specialized epidermal cells that facilitate gas exchange in shoots.

Trichomes - Outgrowths of the shoot epidermis that can reduce water loss and reflect light. These hair-like structures can also help defend against insects.

Vascular Tissue System

Vascular Tissue System - This system facilitates the transport of materials through the plant and provides mechanical support.

Xylem & Phloem - What are the two vascular tissues?

Xylem - Conducts water and dissolved minerals upwards from the roots to the shoots.

Phloem - Transports sugars from where they are made to storage structures or to sites of growth.

Stele - What do you call the collective vascular tissue of a root or stem?

Vascular Cylinder - In angiosperms, the stele of the root is a solid, central .

Vascular Bundles - The stele of stems and leaves is divided into _ , strands of xylem and phloem.

Ground Tissue System

Ground Tissue System - All other tissues neither dermal nor vascular are part of what system?

Pith - Ground tissues internal to the vascular tissue.

Cortex - Ground tissues external to the vascular tissue.

(True) Ground tissue includes cells specialized for storage, photosynthesis, support, and transport.

Common Types of Plant Cells

Cell Differentiation & Specialization - During development, what do plant cells undergo in terms of structure and function?

Parenchyma, Collenchyma, Sclerenchyma, Water-Conducting Cells of Xylem, Sugar-Conducting Cells of Phloem - What are the major types of plant cells?

Parenchyma Cells - Have thin and flexible primary walls and they generally lack secondary walls. They also have a large central vacuole.

Parenchyma Cells - They perform the most metabolic functions and also have the ability to divide and differentiate.

Collenchyma Cells - Grouped in strands and help support young parts of the plant shoot.

Collenchyma Cells - These cells provide flexible support without restraining growth, through their unevenly thickened primary cell walls.

(True) - Collenchyma cells are capable of living past functional maturity.

Sclerenchyma Cells - Are rigid due to thick secondary walls which contain lignin.

Lignin - It is a strengthening polymer found in sclerenchyma cells.

(True) Sclerenchyma cells die at functional maturity.

Sclereids & Fibers - Two types of sclerenchyma

Sclereid - Sclerenchyma cells that are short and irregular in shape and have thick, lignified secondary walls. It’s basically the standard sclerenchyma, by figure description.

Fibers - Sclerenchyma cells that are long, slender, and arranged in threads.

Water-Conducting Cells of Xylem

Tracheids & Vessel Elements - What are the two types of water-conducting cells in the xylem?

(True) Upon reaching functional maturity, Tracheids and Vessel elements die.

Tracheids - Are long, thin cells with tapered ends found in the xylem of all vascular plants.

Pits - Thin regions in tracheids that lack secondary cell walls. It allows for the movement water between tracheids.

(True) Vessel elements are common to most angiosperms, and a few gymnosperms and seedless vascular plants.

Vessel Elements - Water-conducting cells that align end to end to form long pipes. At the end of these pipes are plates that allow water to flow freely through them.

Vessels - Long pipes of vessel elements.

Perforation Plates - These are found at the end of vessels that allow free passage of water through the vessel elements.

Sugar-Conducting Cells of the Phloem

(True) - Cells of the phloem are alive at functional maturity, but lack organelles.

Sieve Cells - In seedless vascular plants and gymnosperms, these cells transport sugars.

Sieve-Tube Elements - In angiosperms, sugars are transported through these tubes/chains of cells.

Sieve Plates - The porous end walls between sieve-tube elements that allow fluid to flow between cells along the sieve tube.

Companion Cell - Each sieve-tube element is connected to this by a plasmodesmata.

(True) - The nucleus and ribosomes of companion cells serves both sieve-tube elements connected to it.

Concept 35.2: Different Meristems Generate New Cells for Primary and Secondary Growth

Indeterminate Growth - The ability of plants to grow throughout its life.

Meristems - These are unspecialized tissues composed of dividing cells. Their activities are the reason why plants can grow continuously.

Determinate Growth - Unlike most plants, most animals and some plants cease to grow at a certain size. This phenomenon is called?

Apical & Lateral - What are the two types of meristems?

Apical Meristems - These meristems are located at the tips of roots and shoots.

Primary Growth - This is the process wherein apical meristems elongate shoots and roots.

Lateral Meristems - These meristems add thickness to woody plants.

Secondary Growth - A process in woody plants wherein lateral meristems add thickness to its parts.

Vascular Cambium & Cork Cambium - What are the two types of Lateral Meristems?

Vascular Cambium - This lateral meristem adds layers of vascular tissues.

Secondary Xylem (Wood) & Phloem - These are the vascular tissues the vascular cambium adds during secondary growth.

Cork Cambium - Lateral meristem that replaces the epidermis with the periderm.

(True) - The epidermis is thinner and weaker than the periderm.

(True) - Cells in the apical and lateral meristems divide frequently during the growing season.

Initials - These are the new cells that remain in the meristem and produce more cells.

Stem Cells - Initials are also called?

(True) - But not all new cells get to be initials. Other new cells may be displaced form the meristem and become specialized in mature tissues.

The Three Primary Meristems

(True) - During primary growth, cells produced by the meristem give rise to three primary meristems that will produce the mature tissues of the plant.

Protoderm, Ground Meristem, Procambium - What are the three primary meristems?

Protoderm - Primary meristem that produces dermal tissue.

Ground Meristem - Primary meristem that produces ground tissue.

Procambium - Primary meristem that produces vascular tissue.

(True) - In woody plants, primary and secondary growth occur simultaneously, but in different locations.

Flowering Plants

(True) - Flowering plants can be categorized based on the length of their life cycle.

Annuals, Biennials, Perennials - Three categories of flowering plants.

Annuals - Complete their life cycle in a year or less.

Biennials - Require two growing seasons.

Perennials - Live for many years.

Concept 35.3: Primary Growth Lengthens Roots and Shoots

Primary Growth - Growth that arises from cells produced by apical meristems and elongates roots and shoots.

(True) - In herbaceous plants, most of the plant consists of primary growth.

(True) - In woody plants, only new, non-woody parts experience primary growth.

Primary Growth of Roots

Root Cap - It covers the root tip and protects the root apical meristem as the root pushes through soil.

Cell Division, Elongation, Differentiation/Maturation - Growth occurs just behind the root tip, in three zones, namely:

Epidermis (Dermal Tissue), Ground Tissue, Vascular Tissue - The primary growth of roots produces?

(True) - The primary growth produces the three main tissues that comprise roots, stems, and leaves.

==Protoderm ==- It is the outermost primary meristem and it gives rise to the epidermis.

70-90% - Root hairs and epidermal cells modified for absorption make up how much of the total root surface area?

(True) - The ==ground meristem== is sandwiched between the protoderm and the procambium. It gives rise to the ground tissue.

(True) - The ground tissue, mostly parenchyma cells, fills the cortex--the region between the vascular cylinder and epidermis.

Parenchyma Cells - Are plant cells that mostly comprise the ground tissue that fills the cortex.

Endodermis - The innermost layer of the cortex. It regulates passage of substances from the soil to the vascular cylinder.

==Procambium ==- The innermost primary meristem. It gives rise to the central vascular cylinder.

Pericycle - A cell layer that surrounds the solid core of the vascular cylinder.

Xylem & Phloem - What comprises the core of a vascular cylinder?

(True) - In most eudicots, the xylem is starlike in appearance, and the phloem is between its ‘arms’.

(True) - In many monocots, a core of parenchyma cells is surrounded by alternating rings of xylem and phloem.

(True) - Lateral roots arise from the pericycle and destructively push through the outer tissues.

Primary Growth of Shoots

Shoot Apical Meristem - A dome-shaped mass of dividing cells at the shoot tip.

(True) - The leaves of the apical bud protect the meristem.

Axillary Buds - They develop from meristematic cells left at the bases of leaf primordia.

(True) - Axillary Buds are kept dormant by chemical communication from the apical bud.

(True) - The closer an axillary bud is to the active apical bud, the more inhibited it is.

Apical Dominance - The power apical buds hold over axillary buds.

(False) - Axillary buds can never be released from the apical dominance.

(True) - Axillary buds are only released from the apical dominance if the shoot tip is removed or shaded.

Lateral Shoots - When the axillary buds have been released from dormancy, it creates?

Stem Growth and Anatomy

Epidermis & Waxy Cuticle - What are two things that cover the stem?

Parenchyma Cells - What are ground tissues primarily composed of?

Collenchyma & Sclerenchyma Cells - Which cells support and strengthen the stem?

(True) - Unlike roots, lateral shoots arise from axillary bud meristems on the stem surface. These do not damage stem tissues.

(True) - In most eudicots, the vascular tissue consists of vascular bundles arranged in a ring.

(True) - In most monocot stems, the vascular bundles are scattered throughout the ground tissue rather than forming a ring.

Leaf Growth and Anatomy

Leaf Primordia - Where do leaves develop from? It’s along the sides of the shoot apical meristem.

(True) - The epidermis in leaves is interrupted by stomata.

Stomata - These are pores that allow CO2 and O2 exchange between the air and the photosynthetic cells in a leaf.

(True) - Stomata are major avenues for evaporative loss of water.

(True) - Each stomatal pore is flanked by two guard cells, which regulate its opening and closing.

Mesophyll - It is the ground tissue in a leaf. It is sandwiched between the upper and lower epidermis.

Palisade, Spongy - What are the two layers of eudicot mesophylls?

Palisade Mesophyll - It is a mesophyll layer found in the upper part of the leaf.

Spongy Mesophyll - It is a mesophyll layer found in the lower part of the leaf. The loose arrangement allows for gas exchange.

(True) - The vascular tissue of each leaf is continuous with the vascular tissue of the stem.

(True) - Veins are the leaf’s vascular bundles and function as the leaf’s skeleton.

(True) - Each vein in a leaf is enclosed by a protective bundle sheath.

Concept 35.4: Secondary Growth Increases the Diameter of Stems and Roots in Woody Plants

(True) - Many land plants display secondary growth.

(True) - Secondary growth occurs in gymnosperms and many eudicots, but is rare in monocots.

(True) - Secondary growth occurs in stems and roots of woody plants, but rarely in leaves.

(True) - Primary and secondary growth occur simultaneously.

The Vascular Cambium and Secondary Vascular Tissue

Vascular Cambium - It is wholly responsible for the production of secondary vascular tissue.

(True) - In a typical woody stem, the vascular cambium is located outside the pith and primary xylem and to the inside of the primary phloem and cortex.

(True) - In a typical woody root, the vascular cambium forms exterior to the primary xylem and interior to the primary phloem and pericycle.

(True) - In cross section, the vascular cambium appears as a ring of meristematic cells, one cell layer thick.

(True) - Division of these cells increases the vascular cambiums’ circumference and adds secondary xylem to the inside and secondary phloem to the outside.

Elongated Initials - These are oriented parallel to the the axis of the stem or root. They give rise to tracheids, vessel elements, fibers of xylem, sieve-tube elements, companion cells, axially oriented parenchyma, and fibers of the phloem.

Shorter Initials - These are oriented perpendicular to the axis of the stem or root. They produce vascular rays, radial files of parenchyma cells that connect secondary xylem and phloem.

Secondary Xylem - The xylem that accumulates as wood and consists of tracheids, vessel elements (only in angiosperms), and fibers.

Early Wood - Wood formed in the spring in temperate regions, has thin cell walls to maximize water delivery.

Late Wood - Wood formed in the summer, has thick-walled cells and contributes more to stem support.