ch 2 bot nomenclature anatomy phys

Practical Horticulture 7th edition By Laura Williams Rice and Robert P. Rice, Jr.

© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458

OBJECTIVES The student will be able to…

•  Locate the genus, specific epithet & cultivar/variety in the scientific name of a plant.



OBJECTIVES The student will be able to…

•  List the principal differences between monocot and dicot plants.

•  Be able to diagram the principal vegetative and reproductive plant parts.

•  Recognize fibrous, tap, and fleshy root systems. •  Explain the processes and importance of

respiration, photosynthesis, translocation, and absorption.



WHAT IS A PLANT?

•  People once thought it easy to tell what was a plant and what was an animal. –  Animals moved, plants did not.

•  There was the plant kingdom and the animal kingdom.

•  Invention of the microscope revealed organisms, neither animals nor plants, with qualities of both.

•  The simple two-kingdom model of life was replaced by three domains: Eukarya, Bacteria, and Archaea. –  Plants fall within the Eukarya domain.

–  There is no universally accepted definition of what a plant is.



WHAT IS A PLANT?

•  Current taxonomic (classification) attempts to group organisms based on phylogeny. –  Evolution of a genetically related group of organisms as

distinguished from development of individual organisms.

•  Some scientists consider only the embryophytes (plants with embryos) to belong to Plantae. –  Others contend it should include some or all green algae.

•  About 350,000 plants are known to exist, and new ones still are being discovered.



WHAT IS A PLANT?

•  As of 2004, scientists have named 287,655 plants. –  258,650 are flowering plants.

–  The rest are mosses, ferns, and green algae.

•  Plants occupy most of the earth’s surface, and are also found in both fresh and marine systems. –  For purposes of this text, the term plant will refer to

a land plant.



PLANT NOMENCLATURE AND CLASSIFICATION

•  Botanical nomenclature is the orderly classification and naming of plants. –  The botanical naming system is not overly complex,

and it does not require any background in Latin.

•  A number of common names are the same as botanical names, such as iris, fuchsia, and citrus.

•  Several reasons for using botanical names in place of common names: –  Universality of botanical names.

–  Precision.

–  Botanical name can give clues to growing requirements.



PLANT NOMENCLATURE AND CLASSIFICATION

•  The requirement for both a genus and a specific epithet to name a species is what defines the system as “binomial” –  Derived from Latin bi = 2; nomin = name.

Example:

Quercus rubra = “red oak”



PLANT NOMENCLATURE AND CLASSIFICATION The Origin and Construction of Botanical Names

•  The branch of botany that deals with the naming of plants is called taxonomy. –  People doing the work are taxonomists.

•  The naming system used dates back 250 years to the Swedish botanist Carolus Linnaeus. –  Who named and published the first references to many

plants using a naming method called the binomial system.




•  The binomial system specifies that a plant name must have at least two parts.

•  In the botanical name for the French marigold, Tagetes patula: –  Tagetes is called the genus

(genera, plural).

–  patula is called the specific epithet. •  When combined, these two

words form the plant species.




•  For ease of understanding, the genus can be thought of as the last name, or surname of a plant, indicating it is related to other plants in that same genus.

•  The specific epithet can be thought of as the first name of the plant, the name distinguishing it from relatives in the same genus.

Genus specific epithet Smith John Catalpa speciosa



PLANT NOMENCLATURE AND CLASSIFICATION The Origin and Construction of Botanical Names Tagetes patula is a small marigold with thumbnail-sized blossoms.

Tagetes erecta is a tall marigold with fist-sized blossoms. While both plants are marigolds, they are so unlike, they are given different specific epithets, and hence, become separate species.



PLANT NOMENCLATURE AND CLASSIFICATION The Origin and Construction of Botanical Names •  New plants, mutations are bred from existing species, and

are being developed constantly.

–  To distinguish them from parent plants, a third part called the variety or cultivar is added to the name.

–  Tagetes patula ‘Lemondrop; –  Tagetes patula ‘Petite Harmony’

•  A plant variety is a naturally occurring mutation or offspring different significantly from the parent.

–  A species with white flowers might spontaneously mutate and a new variety with pink flowers appear.

•  A cultivar is human-made and/or -maintained. –  The name is short for “cultivated variety.”



PLANT NOMENCLATURE AND CLASSIFICATION Writing and Pronouncing Botanical Names

•  The variety of ash tree known as Modesto ash may be written as: –  Fraxinus velutina ‘Modesto’

–  F. v. v. Modesto

–  F. v. var. Modesto

•  The genus or specific epithet is written out once and is abbreviated thereafter.




•  The International Code of Botanic Nomenclature is adhered to strictly when new species are named. –  Genera and specific epithets

must be in Latin-like form.

•  Frequently, a Latin name conveys information about the plant it represents. –  Specific epithets rubra, alba,

atropurpurea & variegata are used to connote colors.




•  Writing botanical names follows a prescribed pattern. –  Genus always is capitalized, followed by the specific

epithet beginning with a lowercase letter. •  Both are italicized (preferred) or underlined.

•  Any variety name follows and may be set off from the species by “v.” or “var. –  The abbreviation “cv.” is used to designate a cultivar.

•  Single quotes around variety or cultivar name can substitute.




•  Another botanical abbreviation is the use of the genus name followed by the word “species,” “sp.,” or “spp.” –  “Species” or “sp.” indicates an unknown species in that

genus.

–  “Spp.” is plural, used to refer collectively to all species of that genus.

–  Botanists disagree on certain pronunciations, but there are guidelines for this.

•  See handout.



PLANT NOMENCLATURE AND CLASSIFICATION Botanical Classification of Plants

•  Ninety percent of cultivated plants have flowers, reproducing by seed. –  A few of the commonly

grown ones do not.

Figure 2-1 Evolutionary English Translations of Common Specific Epithets and Cultivars.

Ferns, the most widely known Pteridophytes, emerged early in plant evolution.

They have a reproductive system based on spores




•  Seed plants are further divided into two groups. –  Gymnosperms are the

smaller of the two groups.


Includes evergreen cone-bearing plants like pines, spruces, junipers and yews.

Foliage generally is needlelike, and they do not have flowers or juicy fruits.

Cycad, podocarpus & Norfolk Island pine are common houseplant types.




•  Seed plants are further divided into two groups.


This group includes all flowering plants & nearly all food plants.

Primary identifying characteristic is the flower, which includes a plant ovary, which swells to become the fruit with seeds inside.

–  Angiosperms make the majority of cultivated plants.




•  Angiosperms are further separated into the Monocotyledoneae and Dicotyledoneae.

•  Monocots are nonwoody plants with short stems and overlapping leaves arranged in a whorl, a form called a rosette. –  Leaves are frequently long & narrow, with parallel veins

running the length.

–  Flower petals are in multiples of three.

–  Fibrous or fleshy root system

•  Included among the monocots are all grasses, lilies, irises, onions, cattails, and most flowering bulbs.




•  Monocots do not produce wood. –  When monocots are what appear

to be woody plants, such as palms, they have an internal stem structure that might resemble Figure 2-11.

Figure 2-11 Cross sections showing arrangements of vascular tissue inside woody dicot and monocot stems.

What appears to be wood in the trunk of a palm is fibrous pseudo-wood, not wood at all.




•  Many dicots grow to a large size. –  Leaves have a branching vein pattern. –  Flowers have parts in multiples of four or five, such as the

four flower petals of apple blossoms.

•  Most trees and shrubs are dicots, as well as most fruits and garden vegetables. –  Their internal stem structure differs from that of monocots.

•  Whether a plant is a monocot or dicot can help determine its method of propagation and susceptibility to weed killers.




•  The classification of plants leads ultimately to the smallest division, variety, or cultivar.

•  Each family groups a number of genera having like characteristics together. –  These families have both Latin &common names.

Figure 2-2 A botanical classification of the tomato cultivar ‘Big Boy.’



PLANT NOMENCLATURE AND CLASSIFICATION Horticultural Classification of Plants

•  Botanists are interested primarily in classifying plants by evolutionary relationship to each other. –  Horticulturists frequently classify plants additionally

according to use.

•  Most cultivated plants are valued for ornamental or for edible value. –  With a few multipurpose plants such as herbs and

ornamental vegetables.




•  Within the edible group, plants are commonly classified as shown here.

The last category, grains, is generally not covered under horticulture.

Grains are classified as field crops and fall under the study of crop science or agronomy.




•  Within ornamentals, the classification system links the plant to its form & use.



PLANT NOMENCLATURE AND CLASSIFICATION Plant Identification •  Determining identity of a plant may be easy if the

plant is commonly grown. –  But becomes difficult and time consuming if the plant

is a wildflower or other uncultivated species.

•  As a first step, cut off a stem with foliage and, if possible, flowers and/or fruits. –  Without flowers or fruits, identification may be impossible.

•  Unless the plant is a foliage houseplant.

–  Enclose the sample in a plastic bag to lessen wilting, having sprinkled it previously with water if possible.



PLANT NOMENCLATURE AND CLASSIFICATION Plant Identification •  Make note of:

–  The relative size of the plant. –  Whether it is woody or nonwoody –  Where it was growing.

•  Sun, shade, marsh, landscape, other relevant conditions.

•  To have the unknown plant identified, begin by showing the sample to a knowledgeable worker at a local nursery. –  If he/she is unfamiliar with it, consult mail-order plant

catalogs, library books with photographs or the Internet. •  If the plant was growing wild, botanical references

called botanical “keys” may be necessary.



Figure 2-4 Vegetative parts of a typical plant.

Collectively these are termed vegetative organs because they are not part of the sexual reproductive system of the plant.

PLANT ANATOMY Vegetative Plant Organs and Their Function

•  Nearly all cultivated plants are composed of a limited number of basic parts, or organs. –  Leaves, stems, buds, and roots.




•  Leaves are the most obvious part of most plants. –  Two main parts are the wide section, termed the blade,

and the petiole, or leaf stem.

•  The angle formed between the petiole & its supporting stem is the leaf axil. –  In the axil will be a bud.

Figure 2-4 Parts of a simple leaf.

The primary function of leaves is photosynthesis.



PLANT ANATOMY Vegetative Plant Organs and Their Function •  A compound leaf is composed of individual leaflets.

–  But will only have a bud at the base of the entire leaf.

Figure 2-5 Types of compound leaves. Photo by Rick Smith.




•  Leaves of cone-bearing gymno-sperms are often scale-like or needle-like.

Figure 2-6 Leaves of gymnosperm plants. Photo by Kirk Zirion.




•  Margin - The outside edge, with characteristics that are a means of identifying plants . –  The margin may be entire (meaning smooth), toothed,

barbed, lobed, or in any other way different from smooth.

–  Barbed or spined margins can also protect a plant from being eaten by grazing animals.




Figure 2-7 Types of leaf margins. Photo by Kirk Zirion.

Barbed Crenate Smooth




•  Veins - The patterns of veins in leaves can be seen by looking closely or holding the leaf up to the light.

Dicot plants usually have a central vein (midvein) with many branch veins.

Figure 2-8a Elm leaf with midvein and branch veins. Drawings by Bethany Layport.

midrib





Some have leaves shaped like the palm of the hand (palmate) with multiple veins of equal size.

Figure 2-8b Maple leaf with three main veins and numerous branch veins.



Figure 2-8c Amaryllis leaf with parallel veins. Drawings by Bethany Layport.



Monocot plants have parallel veins running the length of the leaf.




•  Leaf apex - The tip of the leaf. –  Pointed, blunt, notched, or a number of other shapes.

•  Leaf base - The part of the blade that attaches to the petiole or directly to the stem. –  If the leaf has no petiole it is

sessile.




•  Leaf covering - Any hair, scales, or film on the leaf blade can be considered a leaf covering. –  Almost all leaves have an invisible wax layer, called the

cuticle, which prevents water loss from the leaf surface.

•  A leaf may have hairs (called trichomes) or scales in addition to this cuticle. –  The hairs give extra insulation against water loss and

discourage plant-eating animals by making leaves less palatable.




•  Stomata - The stomatal complex is a minute opening or stoma, and the cells that surround it. –  There are great numbers of these, found primarily

on the undersides of leaves.

•  The central stoma are flanked on either side by guard cells that open and close the stoma according to environmental conditions. –  The stomatal complex regulates the flow of gases

and water vapor in and out of the leaves.




•  Stipules - Small, often leaflike appendages found normally at the base of a petiole. –  Not all plants have stipules.

–  In many species, stipules die, shrivel, and abscise (fall off) relatively soon after the leaf has finished growing.

•  Stipules may have been, in prehistoric times, protection for the leaf bud or emerging leaf. –  Now they may have a minor photosynthetic role or be

modified into spines or tendrils.




•  Modified leaves - Evolved to perform functions other than the photosynthetic function customarily associated with leaves. –  Poinsettia “petals” are modified leaves called bracts.

•  Twining tendrils and spines can also be modified leaves.




•  Growth of stems increases plant height or width. –  The stem transports water and other substances.

•  Also the site of leaf and flower attachment.

–  Some stems are also photosynthetic.

•  Not all stems grow above ground. –  Underground bulbs contain short stems and attached

scales (ie: onion layers), which are modified leaves.

–  The everyday baking potato is an underground stem thickened to serve as a storage site and called a tuber.




•  Shortened stems found in the aboveground portions of plants create the rosette plant form. –  Rosette plants are recognized easily

because of the shortened stem.

•  Leaves appear to grow from one central point and radiate outward like the overlapping petals of a rose.

Figure 2-9 Typical rosette-form plants.

Many plants grow in rosette form, including African violets, cabbages, strawberries, and daylilies.



Figure 2-10 Types of leaf attachment & node locations.

Leaves arranged alternately are attached stepwise down a stem


•  Leaves can be arranged in an opposite, alternate, or whorled pattern on a stem. –  Pattern of leaf arrangement

is important, and is used in identifying plant species.



Figure 2-10 Types of leaf attachment & node locations.

Leaves arranged oppositely grow in pairs.


•  Leaves can be arranged in an opposite, alternate, or whorled pattern on a stem. –  Pattern of leaf arrangement

is important, and is used in identifying plant species.



A bud will be present at each node, although it can be undeveloped and difficult to distinguish.

Knowing the locations of nodes and internodes on a stem is important in pruning and propagation.


•  Whorled leaves occur in groups of 3 or more, that all grow from one point on the stem. –  The site at which a leaf is/was attached is called a node.

–  The section of stem between nodes is the internode.




•  A plant’s vascular system is the network of path-ways that moves carbohydrates, minerals, water, and other substances within the plant.

•  These pathways are divided into xylem and phloem. –  Water and nutrients are moved up in the xylem from

the roots, through the stem, and out to the leaves.

–  Carbohydrate (the plants “food”) is manufactured in the leaves and moves down the phloem to the roots or to other parts of the plant where it is needed.




•  Dicots that will grow into woody shrubs or trees have their xylem and phloem arranged in concentric rings inside the stem when they are young.

Figure 2-11a Arrangement of vascular tissue inside woody dicot stems.

The rings in a tree are made by the secondary xylem laid down in yearly layers in the center of the tree.




•  Monocots have xylem and phloem together in vascular bundles scattered throughout the stem.

Figure 2-11b Arrangement of vascular tissue inside monocot stems.

Both xylem and phloem extend through the stem and all the organs of a plant.




•  The vascular cambium manufactures new xylem & phloem cells to maintain/increase the transporting abilities of the vascular system.

Figure 2-11b Arrangement of vascular tissue inside monocot stems.

The cambium is a thin layer of rapidly dividing cells found between the xylem & phloem areas in the stem.




•  In woody stems, the cork cambium produces bark cells and is found directly beneath the bark surface.

Figure 2-11a Arrangement of vascular tissue inside woody dicot stems.

Technically, the “bark” of a woody plant is all stem tissue outside the vascular cambium.




•  Buds - contain immature plant parts –  A vegetative bud is the site of new leaf and stem

growth. It contains a leaf or leaves and, sometimes, an embryonic shoot.

–  A flower bud includes rudiments of one or more flowers. •  Frequently it is larger than a vegetative bud.

–  A mixed bud contains the potential to produce both a shoot and a flower.




•  The arrangement of buds on a stem places them in either axillary or terminal positions.

Figure 2-4 Parts of a simple leaf. Figure 2-12 Stem with axillary and terminal buds.

Buds which form at other sites, such as along the veins of a leaf or the petiole & leaf blade junction, are called adventitious buds.




•  Roots - the fourth vegetative plant organ. –  The point at which they attach to the aboveground

portions of the plant is called the crown.

•  Roots anchor the plant in position, and absorb and transport water/nutrients for photosynthesis. –  Carbohydrates are stored in older parts of the root system.

•  In the development of a plant from seed, a single primary root is produced first.




•  In many plants, the primary root does not substantially branch, and remains the primary site of anchorage and absorption.

Figure 2-13a Types of root systems.

Such roots, called taproots, are typically found on citrus, dandelions & carrot plants.




•  In most plants, a netlike mass forms, usually called fibrous root systems.

Figure 2-13b Types of root systems.

In grasses, fibrous roots grow from the leftover base of the primary root, left when it died shortly after seed germination.

Lateral side roots grow and create the fibrous system.




•  In most plants, a netlike mass forms, usually called fibrous root systems.

Figure 2-13b Types of root systems.

Roots may also be classified as fleshy, meaning they are thick like taproots, but branch like fibrous roots.




•  Adventitious roots grow from any tissue other than root tissue.

Figure 2-14 Modified roots. Gripping roots allow ivy to climb up a wall. Courtesy Maureen Gilmer.

Adventitious roots of ivy & orchids attach the plants to trees.




•  Adventitious roots grow from any tissue other than root tissues.

Figure 2-14 Modified roots. Orchid roots both attach the plant where it grows and act like sponges to absorb water. Photo courtesy of Bob Hoffman, Huntington Beach Orchids, Huntington Beach, Calif.

Adventitious roots of ivy & orchids attach the plants to trees.




•  Adventitious roots grow from any tissue other than root tissues.

Adventitious prop roots of corn anchor it against uprooting by wind.

Figure 2-14c Modified roots. Prop roots on this corn plant help support the stem. Photo from Wilson, Botany, 5/e. ©1971 Brooks/Cole.By permission.




Figure 2-15 Parts of the root tip.

At the tip of every root is the root cap, made up of a layer of cells that prevents damage to the rest of the root as it pushes through the soil.




Directly behind is the root meristem, producing new cells to replace cells scraped off as the cap pushes against the soil and to lengthen the root.






Beyond the meristem is the zone of elongation.

Cells produced by the meristem lengthen the root in this zone & push the root through the soil.





Water and nutrients are absorbed in the zone of maturation & absorption.




•  Cells in the zone of maturation and absorption form fragile root hairs, about 1/16 inch long, through which water and nutrients enter the plant.

Root hairs often live only a few weeks and are replaced by hairs developing on younger cells.

In this way root hairs constantly contact fresh soil, ensuring a steady supply of nutrients.

Figure 2-16 Root hairs of a radish seedling. Photo by Michael Knee, Ohio State University.




•  Modified Roots - much the same as modified leaves and stems. –  Roots fashioned for storing large quantities of

carbohydrates are the most common. •  Sweet potatoes are an example of this modification.



PLANT ANATOMY Plant Sexual Organs

•  Flowers and fruits are found on most cultivated plants at some time during the life cycle. –  They may appear continuously, seasonally, or only once,

depending on the species and its growing conditions.

•  Flowers are often not essential for the continuation of the species –  Both nature and humans reproduce plants by the

vegetative parts, as in strawberry runners.

•  Flowers are classified by their sexual parts. –  A flower with both male & female parts is called perfect

or bisexual—most species produce perfect flowers.




•  A flower can be exclusively male or female, needing blooms of opposite sexes for seed formation.

•  Some species have male and female blooms on one plant and are called monoecious. –  Examples are cucumber, sweet corn, and pecan.

•  Dioecious species have male flowers on one plant and female on another. –  Plants of opposite sexes are needed to produce seed

on the female. •  These include holly, date palm, bittersweet, and kiwi.




•  Occasionally flowers are sterile—with neither male nor female parts. –  These are frequently prized by gardeners because they

often have double sets of petals.

•  Doubleness is caused by a mutation that causes sexual parts to develop into petals.




•  A typical flower is made up of:

Figure 2-17 Parts of a perfect flower.

–  A central female structure, the pistil.

–  The surrounding male parts called stamens.

–  A nonreproductive collection of parts called the perianth.

The perianth is the corolla (petals) and the calyx (sepals).




•  The typical pistil (or carpel) contains three main parts:


–  The top, called the stigma.

–  The thin vertical shaft, called the style.

–  The bulblike base called the ovary.

Inside the ovary are ovules that will develop into seeds.




•  Stamens are composed of:


–  The anther, at the top, which produces pollen

•  Functionally similar to sperm.

–  The supporting stalk, called the filament.





Surrounding or beneath the sexual parts are the petals and sepals, a leaflike base under the petals.






The colored petals attract insects, which transfer the pollen to the female parts.

They also shield the pistil and stamens from weather.








The sepals form a cover for the developing bud, protecting it from damage.








The sepals form a cover for the developing bud, protecting it from damage. Under the sepals is the receptacle,

the enlarged base on which the flower rests.




•  Not all flowers have easily distinguished parts. –  Instead the parts will

be in various forms due to the divergent evolution of plant families and genera.

Figure 2-18 Two flower forms. Drawing by Bethany Layport.




•  Not all flowers are produced singly. –  They often occur in

clusters. While each flower may be tiny, when grouped they form a showy head.

Figure 2-19 Three types of inflorescences. (a) head, (b) spike, (c) umbel. Drawings by Bethany Layport.

a) Daisy b) Gladiola

c) Onion




•  Following fertilization of the egg, some of the flower components may wither and drop off. –  Including the perianth (all or some) and stamen.

•  The ovary with its newly fertilized eggs continues to develop. –  The maturing ovary will develop into a fruit with one or

more seeds inside.

–  Fruits can be botanically classified most correctly by which parts of the flower develop to produce the “fruit.”

•  Technically “fruit” is a swollen ovary or ovaries.




•  For practical reasons, fruits are classified based on the appearance of the fruit tissue. –  Primary differences are whether fruits are fleshy or dry.

•  Fleshy fruits are those that contain appreciable amounts of water. –  Most eating fruits (plums, strawberries, oranges). –  Most vegetables from which the fruit is eaten (cucumbers,

squash, eggplant). –  Garden plants such as crabapples, roses, and fuchsia.

•  Dry fruits include sunflowers, pecans, and others that contain very little water.



Types of fleshy fruits



PLANT ANATOMY - Plant Sexual Organs •  Fruits are also different in appearance by whether the fruit splits

and releases the seeds at maturity.

•  Called dehiscent if they split at maturity.

•  Called indehiscent if they do not split.

To see a slideshow on the different categories of fruits:

http://www.slideshare.net/guest275ba2/types-of-fruits




•  Fruits are also classified by the position of the seeds relative to the fruit. –  Drupe fruits have a fleshy exterior and a single seed

encased in a hard covering. •  Peaches and plums.

–  Pome fruits mature from a multiple-seed ovary. •  Apples and pears.

–  A berry has one or more seeds in a soft fleshy covering. •  A grape is technically a berry, as is a tomato.

•  Raspberries & blackberries also meet the technical definition.




•  A few fruits are called achenes. –  The seeds can be borne outside the juicy part.

•  A strawberry is called a berry, but is botanically an achene.

•  As is a dandelion (because of the way the seeds form on the head), and the “helicopter” seed that falls from a maple tree.



PHYSIOLOGICAL PROCESSES I. Photosynthesis •  Photosynthesis in the chlorophyll complex is the

process by which plants manufacture carbohydrates (starches and sugars) needed to live and grow. –  Made possible by the green pigment chlorophyll.

•  In the presence of water, light, and CO2, chlorophyll captures light energy and chemically converts it to carbohydrates, producing oxygen as a by-product:

Chlorophyll captures



PHYSIOLOGICAL PROCESSES 2. Cellular Respiration •  Cellular respiration can be thought of as an opposite

reaction to photosynthesis. –  Respiration breaks carbohydrates down into energy.

•  Cellular respiration requires carbohydrates and oxygen, yielding energy, water, and CO2

.

•  The photosynthetic process requires light, but cellular respiration does not. –  Cellular respiration continues constantly in every cell

of the plant, even as photosynthesis is taking place.



PHYSIOLOGICAL PROCESSES Cellular Respiration •  The relative rates of cellular respiration and

photosynthesis govern plant health & growth. –  Correct environmental conditions are crucial for obtaining

a high photosynthesis/low cellular respiration ratio.

•  Maximum photosynthesis can be encouraged by moderate to bright light intensity, sufficient water in the soil, and warm temperatures. –  Cellular respiration can be slowed by cooler temperatures.

•  As lower temperatures decrease photosynthesis, the best growing conditions are warm days and cool nights.



PHYSIOLOGICAL PROCESSES Cellular Respiration •  Occasionally a plant will have a higher rate of

cellular respiration than of photosynthesis. –  Such as a small tree growing in a forest of larger trees.

•  Shading from the larger trees reduces photosynthesis, while cellular respiration remains moderate and steady.

–  All the carbohydrate being produced, plus part of the stored reserve, is used for cellular respiration.

•  The tree stops growing and slowly dies.

–  Another example would be when a plant does not have enough water.

•  The stomata close to prevent water loss, but also deprive the plant of CO2 and slow or stop photosynthesis.



PHYSIOLOGICAL PROCESSES 3. Translocation •  The movement of carbohydrates, minerals, and

water through the plant is called translocation. –  Caused by negative tension, when water vaporizes from

the leaves.

•  Movement of sugars in the phloem is called a source-to-sink movement. –  Sugars are taken from their site of manufacture or storage

(source) to another storage or utilization site (sink). •  One of the primary sinks for carbohydrates is the roots. •  A second sink is developing flowers, fruits, leaves & seeds.

•  A third sink for photosynthesized sugars is the growing regions (meristems) at the stem and root tips.



PHYSIOLOGICAL PROCESSES Translocation •  Source-to-sink movement is seasonally dependent.

–  In spring the roots are the source of stored energy, which moves to the new leaves to fuel their development.

–  In fall the leaves are the source, and movement is to the roots to accumulate carbohydrates for winter storage and use in the following spring.



PHYSIOLOGICAL PROCESSES 4. Absorption •  Water and mineral absorption is the fourth internal

plant process. Primarily a function of the roots. –  Also occurs through leaves by foliar absorption.

•  Absorption and active transport is an energy- and oxygen-requiring process. –  Primarily responsible for absorbing/moving mineral

compounds.

•  Passive absorption/transport is through a process called osmosis, which moves only water through cell membranes. –  The main way plants take in water and move it between

cells.



PHYSIOLOGICAL PROCESSES 5. Transpiration •  Transpiration is the opposite of absorption in that

it involves the loss of water from the plant. –  Water in liquid form in the plant is released into the

air as vapor from the leaves, stems, and flowers.

•  Of all the water taken from the soil by absorption, a relatively small amount is used in photosynthesis –  The rest is lost through transpiration.

•  An increase in the amount of water in the leaf and guard cells is the main reason the stomata open. –  When the guard cells are plumped full of water, they

open the stomata, allowing transpiration to occur.



PHYSIOLOGICAL PROCESSES Transpiration •  Environmental factors such as temperature,

humidity, and wind affect transpiration. –  High temperature increases transpiration. –  High humidity decreases transpiration.

–  Wind usually increases transpiration by drawing newly transpired water vapor from the leaf.

•  Without transpiration, minerals or hormones would not move throughout the plant.

•  Transpiration also helps keep the plant adequately cool by transpiring out of the plant heat used in changing liquid water in the plant to a gas.



END OF CHAPTER

ch 2 bot nomenclature anatomy phys

Education

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plant nomenclature

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plant kingdom

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