5.3.1 PHOTOSYNTHESIS Photosynthesis accounts for more than 90 percent of the dry matter yield of horticultural plants and is the ultimate source of food and fossil fuel. Photosynthesis is the single most important chemical reaction in nature. It impacts the environment significantly through its effects on the oxygen content of the air. This major physiological process is important not only because of its tremendous impact on a variety of functions in nature but also because an understanding of the process enables scientists to maximize its rate for higher crop productivity. Photosynthesis is a reaction occurring in green plants whereby plants utilize water and the energy of sunlight to fix inorganic carbon dioxide in the form of organic compounds, releasing oxygen in the process. In other words, the sun’s energy is transformed by plants through photosynthetic processes into chemical energy usable by other living organisms. The importance of this process is more readily apparent when we understand that plants are ultimately the source of all food. Plants may be used directly as food (e.g., vegetables, fruits, grains, nuts, and tubers) or may be used by animals and then indirectly become available through animal products (e.g., poultry, fish, meat, and dairy products). Lest we limit the importance of plants to food, it should be made clear that plants are also sources of materials for fuel, clothing, and medicines. They are utilized widely in the beautification of the landscape and performance of other functional roles. The general chemical reaction of photosynthesis is Photosynthesis The process by which plants convert light to chemical energy. 6CO 2 12H 2 O green plant light energy C 6 H 12 O 6 6O 2 6H 2 O This reaction occurs in the chloroplasts, using chlorophyll as an enzyme. Carbon dioxide comes from the air and water from the soil. Phases of Photosynthesis Light-Dependent Reactions LIGHT The nature of the electromagnetic spectrum is discussed in Chapter 4. Figure 4–4 shows that visible light is only a small portion of the vast electromagnetic spectrum. Only certain wavelengths of light are involved in photosynthesis. These specific wavelengths depend on the absorption spectrum (the range of wavelengths of light absorbed) of the various pigments involved in photosynthesis. A pigment may absorb a broad range of wavelengths, but certain ones are more effective than others in performing specific functions. The action spectrum of a pigment describes the relative effectiveness of different wavelengths of light for a specific light-dependent process such as flowering or photosynthesis. Light-Independent Reactions The light-independent reactions stage is also collectively called the dark reaction of photosynthesis. At this stage, carbon dioxide is reduced to carbohydrate, a process called carbon dioxide fixation. This stage does not depend directly but rather indirectly on light, since the ATP and NADPH required are produced by the light-dependent reactions. Further, the two chemicals do not accumulate in the cell but are used up as fast as they are produced. The fixation of carbon dioxide (CO 2 ) comes to a halt soon after the light supply is terminated. Carbon dioxide fixation occurs by one of two major pathways, which are distinguished by the first product formed. These are the three-carbon (C 3 ) pathway and the four-carbon (C 4 ) pathway. Carbon Dioxide Fixation A cyclical series of reactions in which carbon dioxide is reduced to carbohydrate. 1. The Calvin cycle. Named after its discoverer, the first product of the Calvin cycle is a three-carbon compound. Thus this pathway is also called the C 3 pathway. Plants that photosynthesize by this pathway are called C 3 plants. Carbon dioxide enters the cycle and becomes covalently bonded to a five-carbon sugar with two phosphate groups called ribulose 1,5-bisphosphate (RuBP) (Figure 5–5). This process (fixation) is catalyzed by the enzyme RuBP carboxylase, also commonly 5.3 Plant Growth Processes 161
called rubisco. Because this enzyme is abundant in chloroplasts, rubisco is said to be the most abundant protein in nature. The overall process can be summarized by the following equation: 6CO 2 12NADPH 12H + 18ATP → 1 glucose 12NADP + 18ADP 18P i 6H 2 O The intermediate product is glyceraldehyde 3-phosphate. Glucose is indicated in the preceding summary equation, but in practice, photosynthesizing cells generate a minimal amount of this sugar. Most of the fixed carbon dioxide is either converted to sucrose (which is the principal form in which sugar is transported in plants) or stored in the form of starch. 2. The four-carbon pathway. Many plants are known to be able to fix carbon dioxide by a pathway whose first product is a four-carbon substance. This pathway is also called the C 4 pathway, and plants that photosynthesize by this pathway are called C 4 plants. First, a CO 2 molecule is bonded to phosphoenol pyruvate (PEP), a threecarbon acceptor compound, resulting in the production of oxaloacetate. The reaction is catalyzed by the enzyme PEP carboxylase (Figure 5–6). C 4 plants are less efficient than C 3 plants in terms of the energy requirements in fixing CO 2 . To fix one molecule of CO 2 ,C 4 plants need five ATPs, whereas C 3 plants need only three. However, C 4 plants have higher photosynthetic rates than C 3 plants and also are able to continue photosynthesizing under conditions such as high temperatures and high light intensity when C 3 plants cannot (Figure 5–7). Generally, C 4 plants are adapted to tropical conditions. Select examples of both categories of plants are presented in Table 5–1. Under hot, sunny skies, C 3 plants undergo a process called photorespiration (lightdependent production of glycolic acid in chloroplasts and its subsequent oxidation in peroxisomes). C 4 plants use CO 2 more efficiently and hence are able to function at only partially closed stomata, as occurs on hot, sunny days. C 3 and C 4 plants are different structurally. The bundle sheath cells of C 3 leaves have small chloroplasts. Photosynthesis occurs only in the mesophyll cells. However, the bundle sheath cells of C 4 plants are large and contain large chloroplasts. These chloroplasts exhibit the Calvin cycle, while the mesophyll cells exhibit the C 4 pathway. All plants known to use the C 4 pathway are flowering plants. In FIGURE 5–5 The Calvin cycle or C 3 pathway of carbon dioxide fixation. 12 NADP + 12 12 NADPH 2 6ATP GA3P 12 ADP + 12P 2 GA3P CALVIN CYCLE 10 GA3P 12 ATP 2 3PGA 6 RuBP 6ADP START 6 CO 2 162 Chapter 5 Plant Physiology
HORTICULTURE Principles and Practic
HORTICULTURE Principles and Practic
With love to Theresa, quarterback;
Brief Contents Preface xxi PART 1 T
Contents Preface xxi PART 1 THE UND
5.3 PLANT GROWTH PROCESSES 160 5.4
8.20 COMMON GREENHOUSE DISEASES 276
12.3 INTERNAL ENVIRONMENTAL CONTROL
PART 6 Summary 541 References and S
22.18 INDOOR COMPOSTING SYSTEMS 668
Preface Horticulture is the area of
ACKNOWLEDGMENTS I am very grateful
PART 1 THE UNDERLYING SCIENCE CHAPT
1 What Is Horticulture? PURPOSE AND
(a) (c) (b) (d) FIGURE 1-1 The many
FIGURE 1 Bridge. The plaza view of
CYCADS Many people mistake these pr
FIGURE 2 The world's largest unbran
FIGURE 2 Sold flowers are loaded on
FIGURE 1-4 Formal landscaping featu
1.4 ROLEOFTHENURSERY AND SEED INDUS
1.5 HORTICULTURE AND SOCIETY Hortic
TABLE 1-3 U.S. Horticultural Export
Turfgrass Operation 1. Landscape te
What Is Horticulture? This site pro
Examples of botanical gardens http:
2 Classifying and Naming Horticultu
Eight major taxa are commonly used
TABLE 2-3 The Divisions of the King
HISTORY OF PLANT TAXONOMY PAUL R. F
AGE OF HERBALISTS Two major events
possible system of nomenclature. Ho
TABLE 1 Type Categories for Plant N
2.3 OTHER CLASSIFICATION SYSTEMS (O
2. Shrubs. A shrub has no main trun
Simple Fruits Fleshy Fruits Drupe B
FIGURE 2-14 A pome, represented by
2.3.5 CLASSIFICATION OF VEGETABLES
(a) (b) FIGURE 2-22 (Source: George
FIGURE 2-25 A narrowleaf plant. (So
FIGURE 2-29 Parts of a typical gras
such as rosemary, sage, thyme, marj
c. Leaves d. Bulbs 2. Cut across (t
Whole plant Organs FIGURE 3-1 Level
ibonucleic acid (RNA), proteins, an
called cristae; this extreme foldin
By virtue of its position, the prim
Phloem Tissue Structurally, phloem
(a) Stalk (b) Culm FIGURE 3-5 Cross
Scale Compressed stem (a) Whole bul
Upper epidermis Palisade layer FIGU
usually occur in xerophytes. In cer
FIGURE 3-22 Selected common leaf ma
FIGURE 3-25 Selected common leaf ti
absorption of water and minerals fr
Outer bark Inner bark FIGURE 3-37 T
Anther Filament Stamen FIGURE 3-41
Exocarp Parts of a typi- FIGURE 3-4
PRACTICAL EXPERIENCE LABORATORY 1.
4.1 CLIMATE, WEATHER, AND HORTICULT
concentration in the atmosphere.A c
TABLE 4-1 Climatic Adaptation of Se
and upward. Another important gener
Rate of photosynthesis mg/sq. dm/hr
and plants that flower under only c
times of the year. Growers start th
content. This section is sometimes
PART 2 PROTECTING HORTICULTURAL PLA
7 Biological Enemies of Horticultur
8. Weeds may clog drains, waterways
is also a root parasite that obtain
LEGISLATIVE Both state and federal
Example Integrated cultural, physic
7.4.2 IMPORTANT INSECT ORDERS Insec
Egg FIGURE 7-3 Life cycle of an ins
sucking insects (also found with so
FIGURE 7-12 Corn earworm damage. (S
TABLE 7-1 Selected Fungal Diseases
7.6.1 SMALL ANIMALS Rabbits, mice,
FIGURE 7-16 The disease triangle. P
fungitoxic exudates in its leaves,
SUMMARY Insects are a major class o
For the home growers or those who c
for consumers and the environment).
TABLE 8-1 Strategy 4: Strategies an
gibberellic acid spray overcomes st
In a competitive industry, a variet
Chemicals gain access to humans thr
2. Pesticide management. Controllin
Every organism has its natural enem
TABLE 8-3 Selected Examples of Biol
1 2 YEAR 3 4 FIGURE 8-5 cycle. A cr
6. Heat treatment. In the greenhous
Organic Compounds (Organics) Organi
under enclosed conditions (e.g., wa
FIGURE 8-9 A tractor-mounted spraye
8.11.9 LANDSCAPE PESTS AND THEIR CO
application, a particular herbicide
Further, they do not provide unifor
SUMMARY Herbicides are chemicals us
Sulfur may be applied for both prev
8.23 PREVENTING GREENHOUSE DISEASES
PART 3 PROPAGATING HORTICULTURAL PL
9 Sexual Propagation PURPOSE AND EX
Anther Microspore Megaspore mother
Lettuce seeds Red light Darkness Fa
FEDERAL AND STATE SEED LAWS Federal
Germination Test In laboratory prac
FIGURE 15 The essential structures
processing into flour or meal). How
physiologically immature seeds must
seeds may be treated in this way be
The two basic modes of seedling eme
locations in the field. Home garden
FIGURE 9-9 A plastic flat. (Source:
(a) (b) FIGURE 9-12 (a) Sowing seed
y the gardener or grower. Whatever
REFERENCES AND SUGGESTED READING Co
species enables vegetative propagat
for rapid rooting. There are two ba
Cutting involving one node (e.g., s
This practice is especially importa
10.6.4 STICKING THE CUTTING Cutting
(a) Indexing by budding Diseased pl
10.11 M ETHODS OF GRAFTING Grafting
Scion Wax FIGURE 10-17 Steps in bar
MODULE 3 BUDDING 10.12 TYPES OF BUD
MODULE 4 LAYERING 10.13 TYPES OF LA
Buried part of shoot is nicked FIGU
variety of ways. In air layering, a
FIGURE 10-34 by using cormels. Prop
Psuedobulbs In the Dendrobium orchi
The technique is used widely in cro
PART 4 GROWING PLANTS INDOORS CHAPT
11 Growing Houseplants PURPOSE AND
TABLE 11-1 Common houseplants Commo
Saddle leaf Philodendron selloum To
Window Displays Plants in windows e
CONTAINER GARDENS DR. TERRI W. STAR
annuals and hardy perennial species
of the large container filled with
perfection about four to six weeks
FIGURE 11-6 Flowers displayed on th
TABLE 11-5 Plant Selected Plants fo
The lighting condition near these w
Fluorescent Lights Fluorescent ligh
may be used for one pot or a group
garden rooms, atriums, or a large c
The photoperiod affects when the ho
patted firm to keep the plant erect
Other Materials Apart from clay and
(a) ( FIGURE 11-25 Support for plan
TABLE 11-7 Common Problems of House
• Keep soil moist all the time
• Prefers high temperatures • P
amount and quality of light. If sup
12 Controlled-Environment Horticult
6. Curvilinear 7. Curved eave 8. Do
Detached greenhouses have several a
12.2.3 FRAME DESIGN There are two b
horticultural business a less-expen
Texas, Hawaii, and California. The
source of heat for times when the t
FIGURE 12-17 Greenhouse production
FIGURE 12-21 Moving tables allowing
Research program on greenhouse engi
greenhouses equipped with a variety
FIGURE 1 Annual energy required per
This system was demonstrated in a 5
FIGURE 6 Amounts of waste energy ut
Ekholt, B.A., D.R. Mears, M.S. Gini
or object to be warmed. Failure to
objects in its path (e.g., the floo
FIGURE 12-27 Motorized ventilation
FIGURE 12-30 Movable internal shade
FIGURE 12-33 A high pressure sodium
Source of Water The quality of loca
FIGURE 12-37 Overhead sprinkler irr
Intermittent Feed Greenhouse plants
However, in winter, greenhouse vent
OUTCOMES ASSESSMENT 1. Explain the
. Foliage or green plants. Foliage
2. Labor. The size of the labor for
FIGURE 13-1 Greenhouse production o
FIGURE 13-2 Lettuce plug is inserte
13.8.4 AGGREGATE HYDROPONIC SYSTEMS
(a) (b) (c) FIGURE 13-6 Plug produc
14 Growing Succulents PURPOSE AND E
FIGURE 14-3 Leaf succulent represen
frost-hardy. Their rosettes are usu
TABLE 14-1 Plant Selected Popular S
(a) (b) FIGURE 14-12 Typical bromel
14.7.1 WHAT ARE CACTI? 14.7 CACTI C
FIGURE 14-16 Opuntia. (Source: Crai
FIGURE 14-23 Mammillaria. (Source:
FIGURE 14-28 Both desert and jungle
Growing mix Gravel Cacti (a) (b) FI
PART5 GROWING PLANTS OUTDOORS: ORNA
15 Principles of Landscaping PURPOS
8. Create recreational grounds. Suc
knowledge, with concern for resourc
(a) (b) (c) FIGURE 15-2 The occurre
GUIDELINES FOR LANDSCAPE DESIGN DAV
the landscape. Some very successful
Rhythm and Line Panoramic view of a
FIGURE 15-10 A formal garden. The e
How frequently do they entertain? A
the patio should be located on the
15.7.1 SELECTING PLANTS A homeowner
Plant Arrangement in the Landscape
Shadow FIGURE 15-15 Planting a tree
SUMMARY Landscaping enhances the su
3. Supply materials on a timely bas
such as preparation rooms (for mixi
of environmental fluctuations. Furt
FIGURE 16-4 A bare-root tree seedli
17 Installation of the Landscape PU
for walks, driveways, and patios (F
Planting may be limited to accentin
17.3.3 PREPARING THE BED The soil s
FIGURE 17-4 Bedding plants raised i
SUMMARY Bedding plants are largely
TABLE 17-6 Selected Ground Covers T
TABLE 17-7 Selected Ornamental Gras
they determine the success and surv
12. Wildlife attraction. Trees in t
pennsylvanica), hackberry (Celtis s
y winds. A stake, which is often a
TABLE 17-8 Selected Narrowleaf Ever
TABLE 17-11 Selected Deciduous Shru
Blooming bushes 1. Blue mist shrub
Planting Bulblets and Bulbils Speci
may be divided such that each secti
FIGURE 18-1 (Source: George Acquaah
Cool-Season (Temperate) Grasses In
Growth Habit Turfgrasses are the mo
Heavy Use Lawns on playgrounds and
The seed should be free from weeds
Source of Sod As with seed, sod sup
A plug of sod FIGURE 18-7 Plugging
way, plants are able to adapt to th
form of a can placed on the lawn wi
TABLE 18-3 Some Common Lawn and Tur
even surface soil surface for layin
MacCaskey, M. 1987. All about lawns
Pruning is sometimes done in conjun
4. Pruning may be done to reduce th
19.4.2 SAWS A saw may be designed t
defeat the purpose of pruning. The
Bud withers as cut end dries back d
19.6 STRATEGIES FOR PRUNING ABOVEGR
Rejuvenation Pruning Cut canes to a
3. In the third and subsequent year
(a) Cut Prune (b) FIGURE 19-16 Step
Eucalyptus and Paulownia are amenab
TRAINING & PRUNING DECIDUOUS FRUIT
Summer pruning eliminates an energy
a) b) FIGURE 2 Newly planted apple
FIGURE 6 Wooden limb spreaders can
FIGURE 9. An apple tree trained to
years to promote continued lateral
Horizontal Espalier The horizontal
19.16.1 CANE FRUITS Cane fruits are
FIGURE 19-26 Shearing of Christmas
pyramid-like form that is wider at
After selecting the appropriate spe
PART 6 GROWING PLANTS OUTDOORS: VEG
20 Growing Vegetables Outdoors PURP
The National Agricultural Statistic
(This item omitted from WebBook edi
growers should take to determine an
pests and reduce/ eliminate hail da
square yard (10 to 68 grams per squ
High tunnels help increase the prof
(This item omitted from WebBook edi
20.4 VEGETABLE MARKET TYPES Fresh V
Establishing the Crop Planting into
home water supply from the tap. Thi
Cole crop Cabbage Root Potato Bean
6. Adequate nutrition. While overfe
variable, ranging from creamy yello
There are two general production pr
This toxin is heat resistant and no
large, or jumbo. The bulb may be sw
REFERENCES Growing selected vegetab
TABLE 21-1 Popular Herbs and Their
(a) (b) (c) (d) (e) (f) FIGURE 21-1
22 Organic Farming PURPOSE AND EXPE
22.3 PRINCIPLES OF ORGANIC FARMING
and the specific materials to be us
22.8 MANAGING SOIL PHYSICAL QUALITY
preemergent or early postemergent o
Composting is a deliberate activity
22.14.5 THE CARBON-TO-NITROGEN RATI
Moisture Supply Water is required b
Compost materials FIGURE 22-4 a wir
As microbial decomposition proceeds
Establishment and Management of an
night, freezing can occur in spring
accomplished by stratification. It
transmitted by the dagger nematode
PART 7 SPECIAL TECHNIQUES AND HANDL
24 Cut Flowers and Floral Design PU
to more than four-fold in standard
Temperature and Humidity Wilting re
FLORAL DESIGN: AN OVERVIEW BY WM. J
Principle Definition Types (or Uses
pH value-a measure of the acidity o
FIGURE 6 Parallel Design-Parallel d
24.3.2 TOOLS AND MATERIALS The tool
3. Establish the focal point. 4. Ad
Natural Drying To dry naturally, fl
24.4.3 DRIED FLOWER ARRANGEMENTS Dr
25 Terrarium Culture PURPOSE AND EX
FIGURE 25-3 Terrarium containers ar
FIGURE 25-5 Assortment of tools use
25.6.7 ENHANCING THE DISPLAY Certai
(a) (b) FIGURE 26-1 Bonsai can be c
TABLE 26-3 Plant A Selection of Pop
26.3.1 COLLECTING BONSAI PLANTS FRO
Strip bark Bare branch FIGURE 26-9
26.5.2 SANITATION It is critical to
27 Postharvest Handling and Marketi
whereas oranges are picked (they ha
(b) (a) (c) (d) (e1) (e2) (f) FIGUR
To reduce packaging injury, contain
is replaced by the by-product of re
Stored produce may lose some color,
with pricing. When selling by volum
(a) (b) FIGURE 27-5 Horticultural p
APPENDIX A Temperature: Converting
APPENDIX B Metric Conversion Chart
APPENDIX D Common and Scientific Na
Pecan (Carya illinoensis) Peony (Pa
GLOSSARY A Abaxial Turned away from
Cellulose A complex carbohydrate th
Floriculture The science and practi
M Macronutrient An essential elemen
Root cap A mass of hard cells cover
INDEX A-frame, 395 A-horizon, 108 A
defined, 390 fertilization, 432-434
Radiant heaters, 378 Radicle, 90 Re
color plate 1 (a) (b) (c) (d) (e) M
color plate 3 (b) (a) (c) (d) (e) (
color plate 5 (a) (b) (d) (c) (e) (
color plate 7 (b) (c) (d) (a) (e) (
color plate 9 (a) (b) (c) (d) (e) (
color plate 11 (a) (c) (b) (d) Grow
color plate 13 (a) (b) (c) (d) (e)
color plate 15 (a) (b) (c) (d) (e)
color plate 17 (a) (b) (c) (d) (e)
color plate 19 (a) (b) (c) (d) (e)
color plate 21 (a) (b) (c) (e) (d)
color plate 23 (c) (b) (a) (d) (e)
color plate 25 (c) (a) (b) (d) (e)
color plate 27 (a1) (a2) (b2) (b1)
color plate 29 (a) (b) (c) (d) (e)
color plate 31 (a) (b) (c) Floral d
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