Transcript Environmental Requirements

Environmental
Requirements




Plant health and development depends on water.
If the main source that makes up 90% of its source is
limited or supplied in an over abundance, the plant
will not be able to adequately achieve its crop yield.
Plants are not the same and do not all require the
same amount of water to survive.
There are many factors that allow plants to tolerate
shortage or excess amounts of water.
 Deep, well-developed root system
 Waxy leaf surface
 Shiny or light colored leaves
The Effects of Water Shortage:
 Cause plant stress
 More susceptible to diseases and insects
 Slow downs photosynthesis
 Wilting: The loss of water pressure in the
plant, causing limpness of the plant tissue
 Death of the plant
The Effects of Excess of Water:
 Cause plant stress
 Reduce oxygen levels for plant and root
growth
 High soluble salt accumulation
 Death of plant
LAB SHEET
“Plant are Needy for Water?”

The amount of water required depends on several
factors:








The type of crop
Stage of the plant
The season of the year
The soil or growing medium
The method of fertilization being used
Watering may be reduced if the weather is cloudy
Small volumes of water cause serious reduction is soil
Proper methods eliminate buildup of high levels of
soluble sales.
Fertilizers
Type of soil
Stage of growth
Season
Fertilizer
Type of plant
Environmental Factors

The growth and development of
floriculture crops is dependent on
light energy.

Light energy enables plants to
make food through the process of
photosynthesis.
 Visible
light (light we see) is a small
segment of all the radiant energy
(rays) given off by the sun.
 The wavelengths of the different
rays are measured in nanometers.
 Based on their wavelengths, the
rays have been placed on an,
Electromagnetic Spectrum.
<>
 Sunlight
contains a complete
blend of visible colors including,
red, orange, yellow, green, blue,
and violet.
 The rays of visible light falls
between, 380 and 780
nanometers.
 Each color has a different range
of wavelengths.
Light is composed of particles called,
Photons.
 Photons carry with them energy
 The energy level increases as the
wavelengths become shorter.
 Example: Blue light has a shorter
wavelength than red light, & therefore
has a higher energy level.

The energy carried by the photons is
absorbed by objects, such as plants
and produces heat.
 Through photosynthesis, plants are
capable of converting light energy
into chemical (food) energy.
 Some lights are absorbed and some
are reflected.

 Objects
that absorb all the colors
except one color, such as green will
appear green.
 The light that is reflected has little
affect on the object.
 In plants, blue & red have the greatest
influence on plant growth.
 Blue:
 Reduces stem length
 Increases branching
 Promotes stem strength
 Improves leaf & flower color
 Red:
 Promotes seed germination
 Seedling growth
 Stem elongation
 A wavelength that is important in plant
growth & development is
 Far-red light
 Far-red light triggers a shade avoidance
response.
 Stems stretch and become weak while the
leaves become thinner and wider.
Plants are responsive to the length of
time they are exposed to light.
 A mechanism in the plant detects the
length of the light period.
 A plant’s response to the length of
light is known as, Photoperiodism.

 Different
plants respond differently to the
length of light.
 Short-day plants (Long-night period)
 Long-day plants (Short-night period)
 Day-neutral plants (unaffected)
Short Day Plant
light
24 hours
critical
day length
dark
No
Yes
No
Flowers?
24 hours
Long Day Plant
light
critical
day length
dark
Yes
No
Yes
Flowers?

Growers control the length of light to
bring on one or more plant responses.
 Keep plant in a vegetative stage of growth.
 Encourage Flowering
 Involves brightness.
 Measured in foot candles
 Is the amount of light distributed by a single
candle one-foot away.
 All
plants have different terms of light
intensity.
 Light intensity can influence plant
development for better or for worse.
 Supplement
lighting is valued in
greenhouse operations located in
low light regions.
 There are numerous light sources:
 Incandescent Lights
 Florescent Lights
 Metal Halide Lamps
 Low/High Pressure Sodium Lamps
Temperature is an important key factor in
plant development and in a number of plant
responses
 Plant responses speed up as temperature
rises & slows down as temperature becomes
cooler.
 This is because enzymes that drive the
reactions are sensitive to temperature.

 A term used to describe a temperature
requirement that produces a plant
response is, Thermoperiodism.
 For some crops, a period of cold
temperature is required for flowering.
 This physiological process is known as,
Vernalization.
 Examples: Easter Lilies & Tulips
 Growers
use temperature to control the
height of plants.
 They do this by managing the difference
between the daytime and the night time
temperatures.
 The mathematical difference between the
daytime and nighttime temperatures is
called, DIF.
 DIF can be positive, negative,
 Positive DIF, is when the day
or zero.
temperature is higher than the night
temperature.
 Negative DIF, is when the day
temperature is cooler than the night
time temperature.
 Zero DIF, is when both day/night are
identical in temperatures.

EXAMPLES:
 Positive DIF- A day temperature
of 78°F and a night temperature of
68°F equals a positive DIF of +10°F (78-68 =
10).
 Negative DIF- A day temperature
of 65°F and a night temperature of
72°F equals a negative DIF of -7°F (65-72 = 7).
 Zero DIF- A day temperature
of 70°F and a night temperature of
70°F equals a zero DIF of 0°F (70-70 = 0).
 Advantages:
 Stem elongation
 Can be used in place of Growth
retardants
 Disadvantages:
 Application is not always possible
 Result in higher heat and cooling
costs
Air has CO2 and O2 that are critical
for photosynthesis and respiration.
 The ability of air to move in and out
of the aid is important in providing
O2 for healthy root growth.
 Roots need O2 to undergo respiration
 Air quality is an ingredient to
producing healthy plants.




CO2 levels can drop significantly when vents
are closed, thus slowing down
photosynthesis.
Ventilation helps replenish CO2
Supplement CO2 can be added
 Results in higher quality crops
 Shorter production time

Usually added between 9:00 am-3:00pm
Humidity, which is water vapor,
affects plant growth
 The growth rate increases under
high humidity conditions
 High humidity reduces water
stress
 Low humidity induces water stress
 Excess humidity increases diseases

Watering is the most important
cultural practice
 Everything depends on H2O
 Water carries material through the
xylem and phloem
 Water makes up a large % of the
cells, tissues, and organs.

 A lack
of water puts the plant
under stress, thus inhibiting the
roots to supply water quickly to
replace water transpired.
 Sever water loss can cause
 Wilting: Is a dropping condition
resulted in loss of turgidity.




Water must be given to plants when
needed.
Timing is critical
Frequent watering can keep growing
medium to wet, lacking good air
exchange
A good rule of thumb is to water the
plant thoroughly when they need water
and wait until they need water before
watering again
 A few
things to consider with
water quality is;

pH of the water
 Should range of 5.8 to 6.2 is adequate.

Soluble Salts
 High soluble salts damage roots
 There
are numerous irrigation methods
 Hand watering
 Spaghetti tubing
 Drip Irrigation
 Ebb and Flood method
 Capillary Mats
 Saucers
 Irrigation boom
 Overhead Sprinklers
 Intermittent mist system