Upload
michael-oduor
View
218
Download
1
Embed Size (px)
Citation preview
8/13/2019 Basic Botany 2
1/92
BOTANY BASICS
David ShiblesMaster Gardener Coordinator
Polk County Cooperative Extension
Adapted from Botany Basics by Dr. Ann MarieVanDerZanden, Extension Master Gardener
Coordinator, Oregon State University
8/13/2019 Basic Botany 2
2/92
THE PLANT WORLD
The plant world is extremely diverse,ranging from one celled algae to huge oaksand sequoias.
It contains plants like mushrooms which haveno green color.
In our gardens we find lichens and mosses,which are green plants, but have no true
roots, no leaves and no flowers.
Many of us grow ferns in our gardens. They
are green plants with true leaves and roots,but no flowers.
8/13/2019 Basic Botany 2
3/92
Finally there are the flowering or seedbearing plants, which make up the vastmajority of plants on earth. These are the
plants that we wish to discuss today.
8/13/2019 Basic Botany 2
4/92
SEED PLANTS-Spermatophyta
The seed plants are those which produce
seeds, each containing an embryo (aminute, inactive plant) that germinates(begins to grow) under favorable
conditions.
Seed bearing plants have true leaves,
stems, roots and vascular tissue.
They consist of two classes-the
Gymnospermae and Angiospermae
8/13/2019 Basic Botany 2
5/92
Gymnospermae-gymnosperms
All gymnosperms are woody, perennial, andwith few exceptions evergreen. Thereproductive organs are borne in structurescalled catkins or in cones.
Their leaves may be fern-like, scale-like,
strap-shaped, or needle shaped. This groupis represented primarily by cone bearingtrees (conifers) and palm-like plants called
cycads.
Members of this group are cypress, cycads,
ginkgo, pine and cedars, podocarpus, yewsand torre a.
8/13/2019 Basic Botany 2
6/92
Angiospermae
The angiosperms include those groups which
have flowers and seeds always protected bya fruit.
They are broken down into two main groupsthe Monocotyledoncae and theDicotyledoncae.
These divisions are determined by thenumber of cotyledons or seed leaves foundin the seed.
8/13/2019 Basic Botany 2
7/92
MONOCOTS
1. Have one seed leaf.
2. Xylem and phloem are paired in bundlesand are dispersed throughout the stem.
3. The floral parts are usually in multiplesof three.
4. The leaves often have parallel veins.
8/13/2019 Basic Botany 2
8/92
DICOTS
1. Have two seed leaves.
2. The xylem and phloem are inside the stem.The ring of phloem is near the bark; the
xylem forms the inner ring.
3. The floral parts are usually in multiples offour or five.
4. The leaves are usually net veined.
8/13/2019 Basic Botany 2
9/92
PLANT LIFE CYCLES
1. Annuals-completes its full life cycle in oneyear. Winter and summer annuals. Summer
annuals include many flowers, crabgrass andspurge. Winter annuals include annual blue-grass and henbit.
8/13/2019 Basic Botany 2
10/92
2. Biennials-produce vegetative the firstyear, then produces seed the seconds year.Examples are Swiss chard, carrots, beets.Weeds include cudweed and bull thistle.
8/13/2019 Basic Botany 2
11/92
3. PERENNIALS - plants that live 2 years ormore and are divided into herbaceous andwoody perennials.
- Herbaceous perennials have soft nonwoodystems that generally die back to the groundeach winter if the temperature is cold enough
and new stems grow from the plants crown inthe spring. Or they may just keep on growing.
- Woody perennials have woody stems that canwithstand cold winter temperatures and includeshrubs and trees.
8/13/2019 Basic Botany 2
12/92
PERENNIALS (cont)
8/13/2019 Basic Botany 2
13/92
INTERNAL PLANT PARTS
Cells are the basic unit of plants. Plant reactionssuch as cell division, photosynthesis, respiration
go on at the cellular level.
Plant tissues such as meristems, xylem andphloem are large organized groups of cells that
work together to perform specific functions.
A unique feature of plant cells is that they are
totipotentSpecialized groups of cells called meristemsare the plants growing points.
8/13/2019 Basic Botany 2
14/92
EXTERNAL PLANT PARTS
Leaves, stems, roots, flowers, fruits, and seedsare known as organs. They can be divided intosexual reproductive and vegetative.
8/13/2019 Basic Botany 2
15/92
Sexual reproductive parts produce seed. Theyinclude flower buds, flowers, fruit and seed.
Vegetative parts include roots, stems, shoot buds,and leaves. They are not directly involved withsexual reproduction.
Vegetative parts can be used in asexual forms ofreproduction such as cutting, budding andgrafting.
8/13/2019 Basic Botany 2
16/92
External Plant Parts-roots
Their principle functions are to absorbnutrients and moisture, anchor the plant,support the stem, and store food. They can beused for propagation in some plants. Themeristematic zone manufactures new cells.
zone of maturation -cells become specifictissues-epidermis,cortex, or vascular
tissue.
zone of elongation -cells increase in size andpush the root throughthe soil.
8/13/2019 Basic Botany 2
17/92
Epidermis-outermost layer which absorbs waterand nutrients.
Cortex cells help move water to vascular tissueand storing food.Root cap protects the end of the root.
8/13/2019 Basic Botany 2
18/92
Root hairs are epidermal cells that occur in asmall zone behind the roots growing tip. They
increase the absorptive capacity of the root. Theyusually live one or two days.Roots often have a symbiotic relationship withcertain fungi - mycorrhizae (fungus + root).
8/13/2019 Basic Botany 2
19/92
Types of roots
1. Primary or taproot-if the primary rootelongates downward and develops few lateralroots then it is called a taproot. Examples arehickory and pecan trees and carrots.
2. Lateral root-is a side or branch root that arisesfrom another root. If the taproot ceases to
grow then a fibrous root system forms.
8/13/2019 Basic Botany 2
20/92
How do roots grow - fertility, moisture and
air spaces.Factors Important For Good Root Growth -1. Roots in water saturated soil may die from
lack of oxygen.2. Roots penetrate much deeper in loose, well
drained soil, than in heavy, poorly drainedsoil.
3. A dense compacted soil can restrict orterminate growth.4. Container plants have a restricted area for
growth and the roots may be more sensitive
to cold damage.5. Keep in mind that plants grow downwardas well as laterally.
8/13/2019 Basic Botany 2
21/92
Vascular System-consists of xylem, phloem,
and vascular cambium.
Xylem-conduct water and dissolved minerals.Phloem-carries food such as sugars.
Cambium-is a layer of meristematic tissue thatseparates the xylem and phloem and produces new
xylem and phloem cells.
The vascular cambium
is important in grafting,because they need to lineup or the graft will fail.
8/13/2019 Basic Botany 2
22/92
Dicots-the vascular system is said to be continuousbecause it forms rings inside the stem.The ring of phloem is near the bark and eventuallybecomes part of the bark.
The xylem forms the inner ring and is often calledthe sapwood and heartwood.This is important to the gardener because herbicideslike 2,4-D kill only dicots.
8/13/2019 Basic Botany 2
23/92
Roots As Food -
An enlarged root is the edible portion of severalvegetables. Sweet potatoes are a swollen tuberousroot: carrots, parsnips, salsify, and radishes are
elongated taproots.
8/13/2019 Basic Botany 2
24/92
STEMS
Support buds and leaves and act as aconduit for carrying water, minerals, and foodfrom photosynthesis. They may be above or belowground.
The vascular system inside the stem forms acontinuous pathway from the roots to the leaves.
8/13/2019 Basic Botany 2
25/92
Stems may be long with great distances between
leaves and buds (branches of trees) or they maycompressed like crowns of strawberry plants,fruit spurs and African violets.
Above ground stems-crowns, spurs or stolons
8/13/2019 Basic Botany 2
26/92
Crowns are compressed stems with leaves and
flowers on short internodes (strawberries,dandelions, and African violets).
8/13/2019 Basic Botany 2
27/92
Spurs are short, stubby side stems that arisefrom a main stem. They are the fruit bearing
stems on pears, apple, cherry trees, etc.
Do not do severe pruning close to fruit-bearingspurs, because the spurs can revert back to
vegetative stems.
8/13/2019 Basic Botany 2
28/92
Stolons are fleshy or semi-woody, elongated,
horizontal stems that often lie on the soil surface.Leaves and roots develop from the nodes (spiderplants, St. Augustinegrass and strawberries).
8/13/2019 Basic Botany 2
29/92
Under-ground stems
Potato tubers, iris rhizomes, and tulip bulbsare underground stems that store food for theplant.
It is sometimes difficult to distinguish betweenroots and underground stems, but one sure wayis to look for nodes. Stems have nodes; rootsdo not.
8/13/2019 Basic Botany 2
30/92
Below ground stems-tubers (potatoes)
The eyes in potato tubers areactually nodes, and each eyehas a cluster of buds.
When growing potatoes fromseed pieces, it is importantthat each piece contain at leastone eye and be about the size ofa golf ball
l d
8/13/2019 Basic Botany 2
31/92
Rhizomes resemble stolons because they growhorizontally from plant to plant. Some are fleshy
compressed (iris), while others are slender andhave long internodes (bentgrass).Johnsongrass is a particularly bad rhizomonousweed.
Below ground stems -
8/13/2019 Basic Botany 2
32/92
Tulips, lilies, and onions produce bulbs, whichare shortened, compressed underground stemssurrounded by fleshy scales (leaves) that envelopa central bud at the tip of the stem.
After a bulb-producing plant flowers, its phloemtransports food reserves from its leaves to thebulbs scale. When the bulb begins growing in
the spring, it utilizes the stored food. So dont cutthe old leaves off until they have withered and died.
Bulbs are classified as tunicate and non-tunicatebulbs.
8/13/2019 Basic Botany 2
33/92
Tunicate bulbs have a thin papery covering
which is actually a modified leaf (narcissus, daffodilsamaryllyis, tulips and onions). This helps protectthe bulb from drying out and mechanical damage.
Non-tunicate bulbs (various lilies) do not havethe papery covering. They have to handled withcare.
8/13/2019 Basic Botany 2
34/92
Corms are another kind
of below ground stem.
Bulbs and corms arecomposed of the same
tissue, but they are notthe same.
A corm is a solid mass of stem tissue with aterminal bud on top. In additional to the terminalbud, axillary buds are produced at nodes.It is protected against injury and water loss by dry
leaf bases similar to the tunic in true bulbs(gladiolus, Watsonia, Tritonia, Freesia,and African lily).
8/13/2019 Basic Botany 2
35/92
Some plants produce a modified stem called atuberous stem (tuberous begonia and cyclamen).These stems are short, flat, and enlarged. Buds
and shoots arise from the crown, and fibrousroots grow from the bottom.
Other plants (dahlias and sweet potatoes) produce
underground storage organs called tuberous roots.These are often confused with bulbs and tubers,however, these are root tissue and not stem tissue.
They do not have nodes or internodes.
8/13/2019 Basic Botany 2
36/92
Stems and Propagation -
Aboveground stems with nodes and internodescan be used to create new plants.
Below-ground stems are also good propagative
tissue. Rhizomes can be divided into pieces,bulblets or cormels can be removed from theparent, and tubers can be cut into piecescontaining eyes.
8/13/2019 Basic Botany 2
37/92
Types of plants and their stems -
Trees have one or two main trunks and are usuallytaller than 12 feet while shrubs have many main
stems and are usually less than 12 feet tall. Bothhave large amounts of hardened xylem in the core.
Herbaceous or succulent stems contain lessor
amounts of sapwood - may only live a year andre-grow from the crown.
Canes are stems with relatively large pith. Theylive only 1-2 years (roses, grapes, blackberries,and raspberries). For fruit production it is good toknow which canes to prune.
8/13/2019 Basic Botany 2
38/92
Vines-have long trailing stems.
Some vines grow along the ground while othersneed a structure to grow on. Twining vines circle
a structure for support.Some circle clockwise (hops and honeysuckle),while other circle counterclockwise (pole beans
and Dutchmans pipe).
Climbing vines are supported by either aerialroots (English ivy and poison ivy), by slender
tendrils that encircle an object (cucumber,gourds, grapes, and passion flower), or by tendrilswith adhesive tips (Virginia and Japanese creeper).
8/13/2019 Basic Botany 2
39/92
Stems as food-The edible portion of several plants,such as kohlrabi, is an enlarged edible, succulentstem.
The edible parts of broccoli are composed of stemtissue, flower buds, and a few small leaves.
The edible part of a potato is a fleshy undergroundstem.
The edible part of cauliflower is actuallyproliferated stem tissue.
8/13/2019 Basic Botany 2
40/92
Buds-A bud is an undeveloped shoot from which
leaves or flower parts grow.
Buds of many plants require a cold period beforethey start to grow in the spring-central Florida
peaches require 250 hours (chill units) below45 degrees).
8/13/2019 Basic Botany 2
41/92
A leaf bud is composed of a short stem with
embryonic leaves. Leaf buds are often less plumpand more pointed than flower buds.
8/13/2019 Basic Botany 2
42/92
Terminal buds are located at the apex of a stem.
Lateral (auxillary) buds are located on the sidesof a stem and usually arise where a leaf meets astem (an axil).
Adventitous buds arise at sites other than theterminal or axil, such as roots, stem internode,edge of a leaf blade, or callus tissue at the end of
a stem or root.
8/13/2019 Basic Botany 2
43/92
Buds as food
Cabbage and head lettuce are unusually largeterminal buds.
Succulent axillary buds are the edible partsof Brussels sprouts.
The fleshy basal part of the flower buds bractis eaten in globe artichoke along with the stem.
Broccoli is probably the most important crop
in Horticulture as the flower bud is eaten alongwith the stem and small leaves.
8/13/2019 Basic Botany 2
44/92
Leaves
Function and structure
The main function of
the leaf is to absorbsunlight to manufactureplant sugars throughphotosynthesis.
A leaf is held away from thestem by a petiole and it isattached to the stem at anode. Where they meet is aleaf axil which contains abud or buds.
Some leaves have hair-like
8/13/2019 Basic Botany 2
45/92
extensions called pubescence.
The cuticle is part of the epidermis and producesa waxy layer called cutin which protects the leaffrom diseases and dehydration.
x
Guard cells regulate
the passage ofCO2, O2 and waterthrough tiny openingscalled stomata.
8/13/2019 Basic Botany 2
46/92
8/13/2019 Basic Botany 2
47/92
Types of leaves
Scale leaves-are found on rhizomes and buds,which they enclose and protect.
Seed leaves-(cotyledons) on embryonic plants.They store food for the developing seedling.
Spines and tendrils-such as those found onbarberry and pea plants, protect a plant or helpsupport its stems.
Storage leaves-on bulbous and succulent plants.
Bracts-brightly colored (dogwoods and poinsettias).
Leaf venation monocots
8/13/2019 Basic Botany 2
48/92
Parallel veined-mostly grasses (monocots) wherethe veins run essentially parallel to each other,(base to apex) except such plants as banana, callaand pickerel-weed, whose veins run laterally fromthe midrib.
Leaf venation-monocots.
Leaf venation-dicots
8/13/2019 Basic Botany 2
49/92
Pinnate veins-veins extend laterally from the
mid-rib to the edge (apple, cherry and peach).
Palmate veins-principle veins extend outward,like the ribs of a fan (grapes and maples).
Leaf venation-dicots
Leaves shape and plant identification
8/13/2019 Basic Botany 2
50/92
lanceolate-longer than wide,tapering toward apex/base
linear-several times longer
than wide-same width
cordate-heart shaped-turnsin an forms a notch where
petiole is attached
ellipitical-2-3 x as long aswide-tapers to acute orrounded apex at base
ovate-egg shaped
Leaf edges
8/13/2019 Basic Botany 2
51/92
entire-smooth edgecrenate-rounded teethdentate-teeth ending in an
acute angle pointing outwardserrate-small sharp teeth
pointing toward the apexincised-cut into sharp
deep,irregular teethlobed-incisions extending
less than half way to
midrib
Leaf base shapes
8/13/2019 Basic Botany 2
52/92
Leaf base shapes
Cuneate-wedge shaped; triangular with the narrowend at the point of attachment.
Obtuse-tapering to a rounded point.
Cordate- turning in and forming a notch
Leaf apex shapes
8/13/2019 Basic Botany 2
53/92
Leaf apex shapes
Acute-ending in an acute angle, with a sharp,but not acuminate point.
Accuminate-tapering to a long narrow point.
Obtuse-tapering to a rounded edge.
8/13/2019 Basic Botany 2
54/92
Simple leaves-the leaf blade is single continuous unit.
Compound leaves-are composed of several separateleaflets arising from the same petiole. Some leaves
are doubly compound.
8/13/2019 Basic Botany 2
55/92
opposite-leaves are position across from each other.
alternate-leaves are arranged in alternate steps alongthe stem, with only one leaf at each node.
whorled-leaves are arranged in a circles along the
stem.
rosulate-leaves arranged in a rosette around the stem,with extremely short internodes.
8/13/2019 Basic Botany 2
56/92
Leaves as food-the leaf blade is the principal ediblepart of several horticultural crops, including chives,collards, dandelions, endives, kale, mustard, parsley,
spinach, Swiss chard and other greens.
The edible part of leeks, onions and Florence fennelis a cluster of fleshy leaf bases.
The petiole is the edible product in celery andrhubarb.
Flower Structure
8/13/2019 Basic Botany 2
57/92
Flower Structure
Collectively the sepalsare called the calyx.
Petals may containperfume-collectively thepetals are called the
corolla.
The flower is very important for plant identification.Flowers of dicots typically have 4-5 sepals and or petals.Monocots typically come in 3s or multiple of 3s.
8/13/2019 Basic Botany 2
58/92
Types of flowers
If a flower has a stamen, pistil, petals and sepals,it is called a complete flower. If one of these
parts is missing, then it is called an incompleteflower.
The stamen and pistal are the essential parts of
a flower for seed production. If it contains bothstamens and pistal, then it is called a perfectflower.
If either the pital or stamen is missing, then it iscalled imperfect pistillate or staminate.
8/13/2019 Basic Botany 2
59/92
Plants with imperfect flowers are classified as:monoecious-have separate male and femaleflowers on the same plant (corn and pecan).
dioecious-species have separate male and femaleplants (holly, ginko, papaya and pistachio)
8/13/2019 Basic Botany 2
60/92
Types of inflorescences:
Some plants bear only one flower called a solitaryflower.
Most inflorescences belong to one of two groups-racemes and cymes. Racemes bloom from thebottom up while cymes bloom from the top down.
8/13/2019 Basic Botany 2
61/92
Pollination-is the transfer of pollen from ananther to a stigma, either by wind or bypollinators.
A chemical in the stigma stimulates pollen togrow a long tube down the style to the ovulesinside the ovary.
When the pollen reaches the ovules, it releasessperm, and fertilization typically occurs.
Cross-pollination-combines genetic material fromtwo parents.
8/13/2019 Basic Botany 2
62/92
Fruit
Fruit consists of fertilized, mature ovules (seeds)plus the ovary wall, which may be fleshy as in an
apple, or dry and hard as in an acorn.
In some fruit the seeds are enclosed within theovary (apples, peaches, oranges, squash and
cucumbers.
In others, the seeds are situated on the outside ofthe fruit tissue (corn and strawberries).
The only part of the fruit that has genes from bothparents is the seed. The rest is maternal.
8/13/2019 Basic Botany 2
63/92
Types of fruit
Simple-develops from a single ovary (cherries,and peaches (drupe), pears and apples (pome),
and tomatoes (berry).
Tomatoes, squash, cucumbers, and eggplants alldevelop from a flower and are considered to be
fruits.
Other types of simple fruit are dry. There wallis either papery or leathery and hard (peanuts/legume, poppies/capsule, maples/samara, andwalnuts/nut).
T f f it
8/13/2019 Basic Botany 2
64/92
Aggregate fruit-develops from a single flower withmany ovaries (strawberries, raspberries, and
blackberries).
The flower is a simple flower with one corolla, onecalyx, and one stem, but it has many pistils or
ovaries.
Each ovary is fertilized separately. If some ovulesare not pollinated successfully, the fruit will be
misshapen.
Types of fruit
8/13/2019 Basic Botany 2
65/92
Multiple fruits are derived from a tight cluster of
separate, independent flowers borne on a singlestructure.
Each flower has its own calyx and corolla.
Examples are pines, pineapples and figs.
Types of fruit
8/13/2019 Basic Botany 2
66/92
Seeds
8/13/2019 Basic Botany 2
67/92
Embryo-is a miniature plant in an arrested state ofdevelopment.Endosperm-is a built in food supply.Seed coat-hard outer covering which protects theseed from disease and water loss.
8/13/2019 Basic Botany 2
68/92
Germination
Germination is a process whereby a seed goes from
a dormant state to an actively growing state.
Before this happen the seed must have water,oxygen and a favorable temperature.
Some seeds such as celery also require light, whileothers require darkness.
8/13/2019 Basic Botany 2
69/92
Radicle-is the first part of the seedling to emerge
from the seed. It develops the primary root andgrows downward.
Hypocotyl-is the structure between the radicle andthe first leaf-like structure and grows upward.
Cotyledons-encase the embryo.
8/13/2019 Basic Botany 2
70/92
Seed dormancy-because seeds are reproductivestructures, they have many mechanisms to ensuretheir survival.
There are two types of seed dormancy:
seed coat dormancy-a hard seed does not allow
water to penetrate. A process called scarificationis used to break this dormancy.
embryo dormancy-these seeds must go through
a chilling before they will germinate.
8/13/2019 Basic Botany 2
71/92
Other factors affecting germination:
age of the seed
seedbed preparation
planting depth
moisture
Plant Growth
8/13/2019 Basic Botany 2
72/92
and Development
Photosynthesis
Respiration
Transpiration
The above 3 itemsdrive plant growth
Photosynthesis=s
8/13/2019 Basic Botany 2
73/92
carbon dioxide+water+sunlight=s Sugar+Oxygen
photosynthates-after producing carbohydrates,
the plant uses them for energy, stores them, orbuilds them into complex compounds (oils/proteins).The plant uses them when light is limited or storesthem in roots or fruit.
Photosynthesis occurs in the mesophyll inchloroplasts which contain chlorophyll.
Chlorophyll is the pigment that makes leaves green.It is responsible for trapping light from the sun.
8/13/2019 Basic Botany 2
74/92
Respiration
Carbohydrates (sugars and starches) made duringphotosynthesis are converted to energy which the
plant uses for cell growth and building new tissue.
This chemical process in which sugars and starchesare converted to energy is called oxidation and issimilar to burning wood or coal to produce heat.
Controlled oxidation in a plant is called respiration.
Respiration does not depend on light so it goes onduring day and night.
8/13/2019 Basic Botany 2
75/92
Photosynthesis produces food stores energy uses water uses carbon dioxide releases oxygen
occurs in sunlight
Respiration uses food releases energy produces water produces carbon dioxide uses oxygen
occurs in the dark aswell as the light
8/13/2019 Basic Botany 2
76/92
Transpiration
When a leafs guard cell shrinks, it stomata open
and water is lost. As water is lost through thestomata, more water has to be taken in throughthe roots.
Transpiration is a necessary process for plants and
8/13/2019 Basic Botany 2
77/92
accounts for about 90% of the water that a plantuses. Transpiration is affected by temperature,humidity, and wind or air movement.
Transpiration is necessary for several things:
Transporting minerals throughout the plant.
Cooling the plant through evaporation
Moving sugars and plant chemicals.
Maintaining turgor pressure.
Environmental Factors Affecting Plant Growth
8/13/2019 Basic Botany 2
78/92
These factors affecting plant growth include includelight, temperature, water, humidity, and nutrition.
It is important to know how these factors affectplant growth and development.
With a basic understanding of these factors, you
may be able manipulate plants to meet your needs.
By recognizing the role of these factors, you may bebetter able to diagnose problems caused by
environmental stress.
Light - Quality, Quantity and Duration
8/13/2019 Basic Botany 2
79/92
Quantity - refers to intensity or concentration andvaries with the season.
Quality-light quality refers to the wavelength.Sunlight supplies the complete range of wavelengths.
Plants absorb blue and red light. Blue light is mainl
responsible for vegetative growth. Red light whencombined with blue light encourages flowering.
Knowing which light source to use is important toknow for manipulating plant growth.
8/13/2019 Basic Botany 2
80/92
Duration or photoperiod refers to the amount oftime the plant is exposed to light.
It was first believed that day length was the main
factor affecting plant flowering. However, it waslater found out that it was the length of darkness.
Plants are classified into 3 day length categories:
Short day length plants flower when they areexposed to less than 12 hr. sunlight (mums, X-mas
cactus, poinsettias)
8/13/2019 Basic Botany 2
81/92
Long day plants flower when the day lengthexceeds 12 hours. This includes most summerflowering plants and vegetables.
Day neutral plants flower regardless of daylength such as tomatoes, corn, cucumber, andsome strawberry cultivars.
Some plants dont fit any category, but mayrespond to combinations of day lengths such as
petunias.
8/13/2019 Basic Botany 2
82/92
8/13/2019 Basic Botany 2
83/92
Temperature
Generally may speed up most processes to a point.
When combined with day length, it may affect thechange from vegetative to reproductive.
Germination:
Generally cool-season crops (spinach, radish,lettuce) germinate best at 55-65 degrees F. Warmseason crops germinate best at 65-75 degrees F.
Flowering:
8/13/2019 Basic Botany 2
84/92
Sometimes day length in combination withtemperature can be used to manipulate flowering.
Christmas cactus can be forced to bloom by
exposing it to more than 12 hours of darkness eachday and a temperature of 50-55 degrees F.
Crop quality:Low temperatures reduce energy use and increasesugar storage. Citrus is sweeter after coldweather.
Adverse temp. may cause stunted growth and poorquality. High temperatures cause bitter lettuce.
8/13/2019 Basic Botany 2
85/92
Thermoperiod - refers to daily temperature change.
Plants grow best when daytime temperature is 10 to15 degrees higher than nighttime.
Under these conditions plant build-up and breakdown tissues at an optimum temperature withrespiration at a nighttime minimum.
Temperatures higher than needed increasesrespiration sometimes greater than photosynthesisso photosynthates are used faster than they aremade.
8/13/2019 Basic Botany 2
86/92
Breaking dormancy - cold period
Hardiness - ability to withstand cold. Less daylightand cooler temperatures stimulate plants toreduce photosynthesis and ship nutrients to twigs,buds, stems and roots.
Water and humidity - needed for photosynthesis,respiration, turgor pressure, solvent for nutrients,cooling factor, regulator for stomatal opening,pressure to help roots move through soil and a
medium for biochemical reactions.
Pl
8/13/2019 Basic Botany 2
87/92
Plants In Communities
Ecology-interaction between plants is important forgardeners. The study of this interaction is called
plant or landscape ecology.
Plant succession-as plants mature you may find thatsome plants will have to be replaced.
Allelopathy-when some plants produce compounds intheir leaves, roots, or both that affect the growthof other plants.
8/13/2019 Basic Botany 2
88/92
Plant hormones and growth regulators-
Are chemicals (natural and synthetic) that affectflowering, aging; root growth; distortion and killingof leaves, stems and other parts; prevention andpromotion of stem elongation; color enhancement of
fruit; prevention of leafing and leaf fall, and manyother conditions.
Th fi f l t th l ti
8/13/2019 Basic Botany 2
89/92
There are five groups of plant-growth-regulatingcompounds:
1. Auxins cause several responses to plants.
a. bending toward a light source(phototropism).
b. downward root growth (geotropism).c. promotion of apical dominance
d. flower formatione. fruit set and growthf. formation of adventitious roots
Auxin is the active ingredient in most rootingcompounds.
2 Gib lli ti l t ll di i i d l ti
8/13/2019 Basic Botany 2
90/92
2. Giberellins-stimulate cell division and elongation,break seed dormancy and speed germination.
3. Cytokinins-occur in both plants and animals.They promote cell division and are often used insterile for growing plants from tissue culture.They are also used to delay aging (senescence).
4. Ethylene-it it only found in the gaseous form.It induces ripening, causes leaves to droop(epinasty) and drop (abscission), and promotes
senescence.
5. Abscisic acid (ABA) is a general plant-growth
i hibit It i d d m d t d
8/13/2019 Basic Botany 2
91/92
inhibitor. It induces dormancy and prevents seedsfrom germinating; causes abscission of leaves,fruits and flowers; and causes stomata to close.High concentration of ABA in guard cells duringdrought stress probably play a role in closure.
8/13/2019 Basic Botany 2
92/92
THE END