Presentation on the Different aspects of light and their influence on plant growth. How the light effects the plant growth. how pant's growth increase and decrease by light different frequencies and intensities

1. Different aspects of light and their
Influence on plant growth.

2. Requirement:
 Plant require light for optimum growth and development,
 But the three different aspects of light quality, quantity
and duration also have significant influence on growth.
 A plant under natural condition receives light from the
sun.

3. Amount, quality, quantity and duration greatly
depends on:
 Season of the year
 Hour of the day
 Geographical location
 Weather

4. Quantity of light:
 Plant use light as a source of energy for
photosynthesis. The term photosynthesis refers to
the reaction between CO² and H²O in the presence of
light to produce carbohydrates and oxygen.
 The rate of this process is highly dependent on the
light quantity. The photosynthesis rate is higher as
the photosynthetic active radiation (PAR) increase.

5. Light Saturation point:
As the intensity of light increase, the
photosynthetic rate eventually reaches a
maximum point. This point where the light
intensity doesn't increase the photosynthetic rate
is called light Saturation point when this point
reached the photosynthesis rate curve becoming
flat.

6. Photosynthetic active radiation:
 Plant photosynthesis between 400-700nm.This range is
known as PAR.-Chlorophyll, the green pigments in the
leaves is responsible for absorbing the PAR, has two
peaks of absorption;
 Blue
 Red
light Leaves absorb little green and reflect it back. This is
why we see the green colors of the leaves.

7. Different colors have different
effect on plant:
✓ Ultraviolet light:-
 Causes DNA damages
 Reduce photosynthesis rate,
 flowering
 Decrease pollinatin
 Seed development is affected
 UV A (A substance of UV light cause plant elongation).

8. ✓Blue Light:-
Photosynthesis process is more efficient due to it.
Responsible for vegetative nd leaf growth.
Import for seeding nd young plants.
✓Red light:-
This is other peak of absorption by the leaves.-
Photochrome (photoreceptor) within leaves is more
sensitive to & responds to red light.

9. ✓Far Red light:
Causes plant elongation.
Trigger flowering in long day plants.

10. LIGHT DURATION AND
PHOTOPERIOD:
 The number of hours of daylight per day which are required
for flowering plants can be divided into three categories.
Based on the required day length needed to trigger flowering.
✓Short day plant:-
 These plants flower only when day length is shorter than
night
 When day length exceed a critical time, plants stops
flowering & go into vegetative growth.
 E.g Rice, Cotton and tobacco.

11. ✓Long day plants:-
These plants flower when day length is longer than night
Example:
Cucumber,corn, raddish and sugarbeat etc.
✓Day neutral plants:-
These plants flower regardless of the day length.-
They usually flower after reaching certain stage of development.-
Eg. Cucumber, corn, sunflower etc.

12. Plant Growth
 Plant growth processes involves the use of light,
carbon dioxide and water to manufacture Food for the
plant use.
 While soil nutrients help to fortify plant structure,
light is an essential component in producing actual
food for the plant.
So, the presence of light can have direct bearing on a
plant’s rate of growth.

13. Photosynthesis
 Food supply
 Leaves absorb energy inside light
 Fuel
 CO2 and H2O source of manufacturing.

14. Effects
 Light color represents different energy frequencies.
1. Red light carry the Lowest energy frequencies.
2. . Blue Violet light carry the high energy frequencies.
3. The energy intensity provided by red light stimulate
overall growth throughout the plant body.
light intensity can vary depending on
•Type of color used
•Wattage amount contained in a bulb.

15. Plant types on the basis of light
intensity:
 A plant's most natural habitat provides the intensity of
light needed for optimal growth.-As a result, different
plants types may require different light intensities.-
 Plants typically fall within one of three lighting
categories.
 •Low light plants.
 Medium light plants
 High Light plants

16. •Low light plants:
Can thrive under a 10-15 watt bulb provided this
amount of wattage reaches each sqft within the
growing area.
•Medium light plants:
Can grow in the 15 watt range but higher intensity of
light can promote faster growth rates.
•High light plants:
Required at least 20 watt per sqft of growing space
though higher intensities will further promote growth
and flowering.

17. Blue light and plant Growth
 Blue photons drive the photosynthetic reactions
 Normal plant growth
 Regulate opening of stomata
 Suppress extension growth
 Act as growth regulator.

18. Blue light and leaf color
 Radiation with shorter wavelength stimulates the
production of compound that influence leaf
coloration.
For example:
 Absence of blue radiation, plants have purplish
Leaves, outdoor may have green leaves.