BIOL 2764 Practical 4 – plant growth analysis
Student number: 816020646
number to the file name when saving for submissions]
*[please also add your student
Demonstrators name: Ajay Ramlogan
Day of lab: Monday
Requirements for write-up and submission of Labs
During the practical session you will be provided with video demonstrations of the methods used
as well as background information on myeLearning. Your demonstrator will also provide you
with data collected using the methods demonstrated. During the practical session you will use
the data to complete the calculations and answer the questions in the lab report. Your
demonstrators can help with calculations and clarifying concepts- however the written answers
must be your own words. All practical reports are to be submitted as word files at the end
of the practical using the link on myeLearning. The penalty for late submission of reports is
as follows: 10% deducted per day late; no acceptance of reports after 7 days.
4.0
Understanding plant growth analysis
Here we use classical growth analysis to investigate the impact of hormones on plant development. We
will use many of the formulas discussed in the Lectures:
Absolute growth rate = (dW/dT) = (W2-W1) / (T2- T1)
[g day-1]
Relative growth rate = (dW/dT) x (1/W) = (W2-W1) / (T2- T1) x (1/W1)
[g g-1 day-1] %
Net Assimilation Rate *also called unit leaf rate [g m-2 day-1]
NAR = (dW/dT) x (1/leaf area) = (W2-W1) / (T2- T1) x (1/ leaf area)
[g day-1 m-2 ]
Leaf Area Ratio
LAR = (leaf area / plant weight (W))
[m-2 g-1 ]
Leaf Area Index = leaf area / ground area
[m-2 m-2 ratio units]
Specific Leaf Area
SLA = (leaf area / leaf weight)
[m-2 g-1 ]
Root: Shoot ratio
(root weight / shoot weight)
[g : g ]
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BIOL 2764 Practical 4 – plant growth analysis
4.1
Collecting data for plant growth analysis
Consult the video myeLearning on harvesting and measuring biomass. Briefly list the steps followed
here: *we will view this in class and suggest some improvements to the methods seen

The true leaves of the sample plants were broken off from the base where the stem is
connected. The stem was also collected using a razor blade to cut it at the base then measured.
Stem was cut in half to fit into envelope.

The roots of the plant should have also been examined by being acquired or scanned.

The dry weight of the plant should have been used for examination instead of the fresh
weight.

The empty envelope was placed on the scale at first then tared to “0” the scale. The stems
were then inserted, weighed, and recorded. That was then repeated using the leaves and the
roots.

A measuring boat should have been used to accommodate all of the plant (I.e., all the leaves
etc.)

The leaves were then placed through the leaf area meter where they were scanned and their
measurements where recorded and summed. This was repeated for the shoots and roots.
Consult the video myeLearning on harvesting and measuring leaf area. Download the software and use it
to measure the leaf are of the leaf provided by your demonstrator, record the leaf treatment and Leaf
here. Measure the Leaf Area for one ’control’ and one ‘GA’ leaf:
Controlled- 20.040 cm2.
GA- 40.21 cm2
4.2
Hormones and plant growth analysis
Here we use classical growth analysis to investigate the impact of hormones on plant development. We
will use many of the formulas discussed above. To investigate the effects of gibberellic acid (GA) spray on
the growth of tomato seedlings. The experiment started with four-week-old seedlings growing in large
pots. 10 pots were randomly assigned to each of three groups:
1. Initial
2. Control
3. GA treated
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BIOL 2764 Practical 4 – plant growth analysis
For ‘3 GA treated’, plants were sprayed with 100ppm gibberellic acid (GA 3) to wet all leaves. Plants in
treatments 1 and 2 were left unsprayed.
Treatment 1, this will be used to estimate the biomass of the plants at the start of the experiment and
provide a reference for the growth that will occur in the two other treatments. These were processed
using the following protocol:
Carefully cut the stem of the plant at the soil level:

Divide each plant into (a) stem (b) leaf plus petioles.

For leaf area index, measure the total leaf area per plant. To estimate leaf area, draw outlines of
the leaves on graph paper then cut out the shapes and weigh them. A separate section of graph
paper of known area is also weighed to give a conversion factor for calculating leaf area.
You will also need an estimate of the ground area occupied by each plant- this is approx. 10 cm 2.
[For 2021- we will use a different method].

For biomass (dry weight), place root, stems, and leaves separately into labelled paper bags and
dry at 80°C to constant mass (you need only 2 paper bags). Dry mass will be taken after two
weeks (note: constant mass will be achieved after 2-3 days, but the material can stay in the oven
until the next Lab session).
After one week of growth this same protocol was followed for treatments 2 and 3.
4.3.1 Calculate growth indices (part 1)
Using the formula from 3.0 and the data provided by your demonstrators calculate Absolute growth rate
and the Relative growth rate for treatment 1 and treatment 2. Fill-in the values in the table and show
your calculation here:
Absolute growth rate = (dW/dT) = (W2-W1) / (T2- T1)
[g week-1]
= (542-428)/(5-4) = 114
Relative growth rate = (dW/dT) x (1/W) = (W2-W1) / (T2- T1) x (1/W1)
= (542-428)/(5-4) (1/428)= 0.27
Table 4.1 Growth indices (using raw data) (*add units in the first row).
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[g g-1 week-1] %
BIOL 2764 Practical 4 – plant growth analysis
Growth index
Tomato
Initial
Control
GA treated
Total mass (week 2)
542g
617g
AGR
114 g week-1
189 g week-1
RGR
0.27g g-1 week-1
%
0.44 g g-1 week1
%
Total mass (week 1)
428g
4.3.2 Calculate growth indices (part 2)
Using the plant growth analysis calculator on myeLearning (from Hunt, R., Causton, D. R., Shipley, B., &
Askew, A. P. (2002). A modern tool for classical plant growth analysis. Annals of botany, 90(4), 485-488),
calculate the remaining growth indices and fill in the table below.
*Note you will need to enter the data from the two treatments separately as the calculator averages all
data entered (i.e. assumes all data is from one treatment).
*Note measurements made at both times (weeks 1 & 2) are used for calculation of AGR, RGR and NAR.
Use data only from week 2 to calculate the other indices- to see these look at the sheet [results_copy]
and view eh week 2 values (F2, P2, Q2):
Table 4.2 Growth indices (using log values; Hunt et al., 2002) (*add units in the first row).
Growth index
Tomato
Control
GA treated
Total mass (week 2) g
542
617
Leaf area (week 2) cm2
518.5
614
RGR g, Rbar/week
3.98
4.11
ULR (NAR)
g/cm2/week
6.25
6.41
LAR cm2/g
9.67
10.05
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BIOL 2764 Practical 4 – plant growth analysis
SLA cm2/g
23.45
24.69
Root: shoot ratio
0.89
0.44
Give short statements to describe and/or explain the effects of the gibberellic acid treatment on each
of the following indices (from results given in Table 4.1/4.2)
Absolute growth rate
This index represents the increase in a plants mass per a unit of time. Gibberellic acid treatment
in plants should result in the absolute growth rate increasing due to growth being induced or
facilitated.
Relative growth rate
This index describes how efficient the growth of the plant is or the amount of new dry mass the
plant grows over time. Gibberellic acid treatment should result in the relative growth rate being
increased.
Net assimilation rate
This is a measure of the increase in plant dry weight per unit leaf area. This index measures the
photosynthetic efficiency of the plant, gibberellic acid treatment should result in the net
assimilation rate increasing thus there would be a higher rate of photosynthesis due to more GA
inducing more growth and leaf area.
Leaf area ratio
This is a measure of how much of the photosynthetic products are utilized in the production of
more leaf area, gibberellic acid should result in the leaf area ratio being increased as there would
be more photosynthesis occurring so more growth would be facilitated.
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BIOL 2764 Practical 4 – plant growth analysis
Specific leaf area
This utilizes the treatment data to measure how much of the area or dry mass of the leaf is
produced for each gram of leaf tissue, this index influences growth rate on total leaf area for
plants affecting light interception and the efficiency of its use. It is also expected for this index to
increase when treated with gibberellic acid since more growth would be facilitated.
Root: shoot Ratio
This index numerically compares the shoot mass to the root mass after treatment, since GA
induces plant growth in the shoots but not specifically in the roots, it would be expected that the
ratio favours or be larger at the shoot side since shoot mass would increase at a faster rate than
root mass.
Summarize the major effects of the GA treatment on growth of the plant species:
Gibberellic acid is a plant hormone that stimulates plant (shoot) growth and development, and it is a
tetracyclic di-terpenoid compound. GA treatment resulted in overall shoot elongation in the plant
species as seen in the results obtained such as an increase in:

Total mass (g): 542 to 617

Leaf area cm2: 518.5 to 614

RGR g, Rbar/week: 3.98 to 4.11

ULR (NAR) g/cm2/week: 6.25 to 6.41

LAR cm2/g: 9.67 to 10.05

SLA cm2/g: 23.45 to 24.69
And a decrease in the root: shoot ratio: 0.89 to 0.44.
4.4 REVIEW- understanding and calculating plant growth indices
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BIOL 2764 Practical 4 – plant growth analysis
When you have reviewed your lecture notes and completed the lab- so that you are familiar with
understanding and calculating the plant growth indices, go to myeLearning and complete the ‘LAB4
MATCHING QUIZ-Plant Growth Analysis’.
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