This document discusses environmental parameters that affect plant growth in greenhouses, including light, temperature, and air composition. It describes how light intensity, spectrum, and photoperiod impact photosynthesis and plant development. It also explains different lighting options and methods for controlling temperature, such as active heating/cooling systems or passive techniques like water storage and shading. Optimum temperatures ranges for plant growth are discussed along with the effects of temperature on physiological processes.

1. 1) Environmental parameters for optimum plant growth .
2) Photoperiodism , vernalization
3) Greenhouse and polyhouse material designs and fabrication
4) Cooling , shading , misting , drip irrigation , fertilization and
fumigation
5) Recording and computerisation of environmental parameters
and cultural operations
6) hydroponics
7) Pots potting mixture and soil sterilization
8) Cultivation of horticultural plants
9) Hardening of tissue cultural derived horticultural plants
10) Post harvest technology
11) Packaging and transportation
12) Intellectual property rights

2. Ght topic -1
Environmental parameters for
optimum plant growth

3. Green house

4. Heating of green house

6. Constituents of environment in a greenhouse :- the microclimate of plant
is specified in terms of (1) light ,(2) temperature ( 3) air composition and(4)
the root media .
Light:- light is most important environmental factor for plant growth .
Sunlight is the only source as far as open field cultivation is concerned .
Whereas electrical lights in addition to sunlight could be used in
greenhouse cultivation whenever required .the availability of sunlight at
particular place is time dependent mainly owing to different season ,
lattitude ,atmosphere humidity and cloud cover .
Light can affect the growth and development of plant in following terms :-
1) Intensity of light
2) Spectrum of light
3) Duration of light and dark period .
Intensity of light :- Typical response of a plant to the intensity of sunlight
shows that the photosynthetic rate for a plant saturate at a particular
level of light intensity .keeping other environmental parameters

7. constant , the photosynthesis process would remain to be at peak
level as long as the light intensity does not fall below the saturation
level .
The light saturation point would be different for different plant
species . The intensity of light can be measured in lux , foot candles
or lumens .

8. Light sources

9. Spectrum of light :- the solar energy used by
plants comprises a small part of total spectrum as
shown as in the fig –

10. The response of plants towards light is not similar human eye .
Plants do not respond to light but they respond to the wavelength .
The different biological and morphological activities of plants
require different wavelength of radiation .

16. cycle of light and dark duration:- it is important for most
of the plants though some plants require long light
duration (long day plants ) , some require long dark
duration ( short day plant) and some plants do not
depends on such type of cycle of light and dark periods
(day neutral plants) for flowering . This response of plants
towards light for flowering is called photoperiodism .
In a greenhouse , light can be controlled in all the above
mentioned terms .
Shading :- partial shading is provided to reduce the
intensity of radiation in the growing area .it can be done
in two ways :-

17. 1) Application of shading paints to greenhouse glazing surfaces .
2) Installing a shading screen or net over / under the greenhouse
frame .
the light intensity can be increased by adding light to the
greenhouse using artificial sources of light. There are many
different types of lamps/tubes as source of light .some of
them are mentioned here :-
a. Incandescent lamps:- only 7% light to energy conversion ratio
.high proportion of red and far red wavelength causing tall and
soft growth .

19. b) Fluorescent lights :- 20% light to energy conversion ratio ,
suitable spectral quality for green house and most widely used in
greenhouses . Available in a wide range of designs and capacity.

20. Spectrum of Fluorescent lights

21. c) high pressure sodium lamps :- 25% conversion ratio ;
long life ; 400w to 1000w.more spectrum of 600 and 800
nm.

22. d) Low pressure lamps :- 27% conversion .yelloyish light ; very
efficient and are used widely . High quality and high fresh weight
plants .

24. e) Metal halide :- 20% conversion ratio ; many sizes upto 2000w ;
costly .400 to 800nm . Most of that 600nm .

25. d) High pressure murcury lamps :- available in 400w to 1000w .
350 to 450 and 550 to 650 nm .

27. All lamps have their typical light spectrum . So
that they can be selected as per requirements
.
The photoperiod can be extended by using
source of light

28. TEMPERATURE:- temperature refers to the relative hotness and
coldness of an object . It is a means of relative intensity of heat
between the two or more objects . It is expressed by °C ,°F and K .
In greenhouse cultivation , temperature at which plant can grow
depends upon many factors :-
1) Species , cultivar and clone .
2) Available radiant energy (light) which is influenced by species
planting arrangement , density , greenhouse structure and its
cover , and climatic conditions of the location .
3) Water availability .
4) Carbon dioxide concentration .
5) Stage of growth , age , and the particular plant structure .
6) Nutrition of crop , fertilizer application and waterquality .

29. Plant temperature :- the energy exchange between a single
plant and its surroundings take place by means of absorption ,
reflection , transmission , conduction etc till the equilibrium is
retained . the biochemical reaction in plants also absorb or release
heat and change the temperature . The capacity of plant to store
heat depends on its mass . Therefore temperature of thin leaves will
vary faster than thick leaves .
Effect of temperature :- temperature affects all the physiological
processes of plants .these include photosynthesis ,respiration ,
translocation , ion uptake , transpiration ,pigment formation ,
reproduction , bulbing , elongation and many others .temperature
influences all these processes in various ways and to different
degrees . Over a limited range at which plant growth will occur ,
biochemical process will commonly be doubled for every 10 °C rise
in temperature .respiration shows a continuous rise as temperature
increases and the same is true with photosynthesis . But
photosynthesis can also be limited by available energy and CO2
concentration .

30. high temperature increases transpiration by rising leaf temperature
and vapour pressure inside it . If the soil is cold , water and ion
uptake , and root growth will be reduced .the effect of temperature
on elongation processes will vary with the plant part about which it
is concerned . (1.22 ,1.23).
Optimum temperature :- optimum temperature refers to the
best temperature at which plant can grow under particular type of
climatic conditions .the optimum temperature range for different
species is different but some general conclusions are :-
a) most species require diurnal temperature fluctuation .
b) Optimum temperature usually varies with season and location .
c) Optimum temperature varies with age .
d) Optimum temperature varies with stage of growth .
e) Optimum temperature varies with the particular process such
as rooting , germination , floral initiation , bulbing etc .
f) Optimum temperature varies with the grower objectives .

36. control of Temperature in green house :- the temperature is
controlled either by increasing or by decreasing it in greenhouse . It
can be done by following methods which are of two types:-
a) Active methods
b) Passive methods
Active methods :-
Increase in temperature :- the temperature can be increased by
following methods :-
1. Use of heater with fan :- in this method a heater with a fan is
used . The fan inflows the hot air inside the greenhouse and
increase the temperature .
2. Use of boiler :- the black painted metal (GI) pipes are laid down
in the greenhouse . The hot water form boiler is flowed into the
pipes . The pipes are heated up and release heat by radiation
which increases the temperature of the greenhouse .

37. Heating methods
Passive heater

38. boiler

39. Decrease in temperature :- it can be done by following methods :-
1.Minimization of direct beam radiation :- the entry of direct
radiation can be controlled through use of movable screen and
temperature increase can be controlled .
2. Evaporative cooling :- this can be done by following methods :-
i. Pad and fan system :- in this method a cooler with evaporative
pads over whichwater is passed by a small circulating pump and
fan is provided on the other side of the greenhouse . Air enters
through the cooling pads gets cooled and taken out through the
exhaust fan covering entire length of greenhouse and cools it .
ii. The another way of achieving evaporative cooling is to cover
the roof of greenhouse by gunny cloths and spraying water over
it . The heat is dissipated from the greenhouse air and cause
water to evaporate from the gunny cloth which , in turn ,
provide cooling effect .

40. Pad and fan cooling

41. Pad and fan cooling

42. Pad and fan cooling

43. Pad and fan cooling

44. Control of temperature by passive methods :- following
are some passive methods to maintain the temperature .
1) Water storage :- the water is used to store and release heat ,
during day ,excess heat is stored in water which is released at
night . It reduce temperature hike in day and temperature fall
during night .3.3
2) Latent heat storage material :-latent heat materials are an
alternating heat storage medium . Materials like CaCl2 .6H2O (
with a melting temperature of 29.7°C and a latent heat of
170kj/kg) have been successfully used in many installations .
These are placed underground on an insulated area . Hot air is
circulated through the storage . Heat is absorbed during day
and released in night .3.4
3) Buried pipe ground storage :- using plastic or aluminum buried
buried pipe at depth of few meters in soil , excess heat from air
is transferred in the ground and released when required .3.5

45. 4) Rock bed storage:- 20 -100 mm thick gravel rock bed is placed
under the greenhouse at a depth varying between 40-50cm .
Gravels are enclosed in an insulated concrete storage enclosure
.during day excess heat is stored and during it is released . 3.6
5) North wall storage :- north wall is internal painted black to store
heat during day and releasing during night . 3.7

46. 3. Air composition :- gaseous composition of the air surrounding
the plant are ; CO₂ ,O₂ ,N₂ , water vapour and other trace gases
.these influence the plant metabolism significantly .
CO₂ is most important gas for plants . It is utilised in
manufacturing of food .as the amount of energy increases , the
supply of CO₂ must increase . The general relationship between CO₂
Concentration in air , light intensity and photosynthesis is shown in
the figure 1.11.
in the open field ,the concentration of CO₂ remain 300 ppm . Which
is sufficient to meet the requirement of plants . But in closed
environment (greenhouse) , CO₂ concentration may hike upto
1000ppm because of respiration overnight and it may fall down to
such a level that plants may become CO₂ deficient afternoon . 1.12.

47. Factors affecting CO2 uptake :- the co2 uptake by leaves
depends upon several factors :-
I. Plant species and variety .
II. Radiation intensity .
III. Wind velocity .
IV. Water stress.
V. Co2 concentration in air.
VI. Resistance to co2 diffusion through the stomata .
VII. Leaf area .
temperature has the direct influence on photosynthesis as
chemical reactions increase with temperature increase .
The co2 uptake also varies with light intensity . If identical
plants are placed in different environment for a period ,
and then both return to same conditions then , both will
not respond similarly .1.14

48. As the internal water potential decreases photosynthesis begins
decrease . High water stress limits photosynthetic rate as light
intensity increases . 1.16
Wind velocity also influence the co2 uptake . There is a
continuous increase in co2 uptake as wind velocity increases
.table 1.6
Co2 enrichment(fumigation):- normally , co2 enrichment
begins at or little after sunrise and continue till one hour before
sunset .the enrichment is not practiced during ventilation .
Various enrichment methods are discussed below .
Combustion :- a hydrocarbon , such as natural gas , paraffin oil or
kerosene , when burnt in the presence of sufficient oxygen , the
CO2 and H2O are produced as a result . A gas burner is used to
burn LPG or NG to produce CO2 . The quality of fuel should be of
high purity .the sulphur content

49. Of natural gas must not exceed 65mg / 30m² of gas and
fuel must burn completely . Otherwise , toxic gas
produced through incomplete combustion may be
hazardous to the plant growth .
Liquid CO2:- when CO2 is filled in bottles and tanks
under high pressure , it liquifies . The gas is released
from the pressurized tanks with the help of regulating
valves so that gas at low pressure is spread inside the
greenhouse .
Solid CO2 :- carbon dioxide under pressure at low
temperature gets solidified and it is popularily known as
dry ice . It can be used for enrichment of CO2 . Air
circulation is needed for even distribution of CO2.

50. Humidity :- it is also an important element in the
greenhouse climate . Humidity is the amount of moisture
present in 1kg of air. Relative humidity is the ratio
between actual vapour pressure and the vapour pressure
of water in air if the air is saturated at same temperature
and is expressed in % .Humidity inside the greenhouse is
influenced by outside climatic parameters . It increases
when warms due to evaporation and reduced when soil
cools .
Humidity affects leaf area development and stomatal
conductance thereby interfering with photosynthesis and
dry matter production . High humidity can cause yield loss
in tomato and fungal and other diseases in greenhouse .
Transpiration increases humidity in greenhouse .

51. To reduce humidity ventilation and increase in
temperature is used .
Humidity is increased by evaporative pad cooling system ,
watering and misting inside the greenhouse .