Leaf area determination in fruit crops
Aim of the experiment:
To determine the leaf area of fruit crops by adopting different methods.
Important information:
The
plant parameters such as leaf area (LA) or leaf area index (LAI) play an
important role in understanding photosynthesis, light interception, water and
nutrient use and crop growth. A better understanding of the relationships
between crop development and environment is thus important. Both LA and LAI can
be measured directly by using digital meters (destructive methods) and
graphical methods or indirectly using developed regression techniques
(non-destructive methods).
Determination of leaf
area by leaf area meter:
In
direct method (destructive methods), leaves are removed from the plant and
measurements are done using digital leaf area meter or hand leaf area meter. Leaf
area meter provides leaf area measurement through electronic rectangular
approximation this instrument can also be used to measure the area of non-transparent
flat surface material like cloth/paper/plastic/leather etc. A leaf area meter
provides a non-destructive means for environmental scientists and farmers alike
to ascertain plant health, quality and local ecological trends as reflected in
the leaf’s area, length, average width and maximum width.
In
principle the leaf is placed between a light source and a photocell, the
reduction in photocell output due to the presence of the leaf then gives a
measure of leaf area. The transmission of light through the leaves is a source
of error, and an attempt to minimize this is usually made by fitting a magenta
filter between the leaf and the photocell to absorb any green light passing
through the leaf.
Leaf
area measurement of plants are useful for many scientific disciplines.
Monitoring the distribution and changes of leaf area is important for assessing
growth and vigour of vegetation on the planet. It is fundamentally important as
a parameter in land-surface processes and climate models.
This
variable represents the amount of leaf material in ecosystems and controls the
links between biosphere and atmosphere through various processes such as
photosynthesis, respiration, transpiration and rain interception. A measurement
that is seemingly so simple and fundamental is really the backbone that
provides the framework for further research in areas like ecology, agronomy,
entomology, carbon cycle research and plant pathology. These and many other
disciplines rely on the measurement of leaf area in much of their work.
The
steps for the digital leaf area meter are as follows;
1. On your digital leaf area meter 30 min for warmup prior-to taking observations.
2. Calibration
of the digital leaf area meter.
3. Then
select the appropriate glass plate and place it on the dark plate.
4. Place
the leaf upside down on the dark plate then place the glass plate on the leaf
so as to press it.
5. Then
pull the shutter of the digital leaf area meter out, the leaf area will be
displayed on the screen.
Determination of leaf
area by graph paper method:
Leaf
area can be calculated by grid or graph paper technique. In this method the leaves
are removed and the leaf outer lamina was drawn in the graph paper then the
leaf area is counted manually. The bigger square represents the area of 1cm2,
while the smaller one represents the area of 1mm2. The total leaf
area can be calculated by adding all the squares.
While
calculating leaf area, a box occupying area more than half the area of a
complete square box was taken equal to area of a complete square box. The area
of a half square box was taken exactly half the area of a complete square box,
while the box occupying area less than half area of a complete square box was
discarded.
Determination of leaf
area by empirical formulae method:
The
developed equations were used to estimate the leaf area and LAI separately. The
equations are already being developed for many crops. By using graphical and
leaf area meter 1st the equations constant is determined then verified
and recommended.
The
formulae for a few fruit crops are mentioned below;
|
Fruit
crop |
Cultivar |
Formulae |
R2 |
Remarks |
|
Banana |
Basrai |
0.0266
+ 0.7629 Leaf width |
0.980 |
Potdar M.V., Pawar K.R., Non-destructive leaf area estimation in banana, Sci. Hortic.45 (1991) 251–254 |
|
Strawberry |
General |
1.89
+ 2.145 × (upper lobe length) × (left lobe width) |
0.993 |
Demirsoy H., Demirsoy L., Ozturk A., Improved model for the non-destructive estimation of strawberry leaf area, Fruits 60(2005) 69–73. |
|
Guava |
General |
16.44
– 3.11 L + 0.58 L2 L= length of the leaf midvein |
0.961 |
Kobayashi K.D., Estimating leaf area of ‘Beaumont’ guava, Trop. Agric. 65 (1988).173–175 |
Assignment:
1.
Determine the leaf area of 5 fruit crops by
adopting the different methods and compare the accuracy.