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Journal of Medicine and Biology
Research Article | Vol 5 Iss 1
Citation: Kasim Roba Jilo, Impacts of Some Environmental Factors and Age of Plants on Nectar Volume and Concentrations of Croton
Macrostachyus. J Med Biol 5(1): 1-8.
© 2024 TRIDHA Scholars
1
Impacts of Some Environmental Factors and Age of Plants on Nectar Volume
and Concentrations of Croton Macrostachyus
Kasim Roba Jilo
Holeta Bee Research Center under Oromia Agricultural Research Institute
Correspondence should be addressed to Kasim Roba, Holeta Bee Research Center under Oromia Agricultural Research Institute,
P.O. Box-22, Holeta, Ethiopia
Received: January 22, 2024; Accepted: March 05, 2024; Published: March 12, 2024
ABSTRACT
Nectar concentration is highly influenced by environmental factors and the objective of the study was also to evaluate
influences of some environmental factors on nectar volume and concentrations of Croton macrostachyus Hochst. ex Delile.
Effects of temperature, relative humidity, daylight time, layers of trees, plants age and soil moisture on nectar volume and
concentration of youngest, medium, and oldest age of croton was measured. The result indicated that nectar concentration
and volume of youngest age was not more affected by temperature and relative humidity like that of medium and oldest ages.
Temperature and age have a significant effect on volume (p = 0.0001) and their interactions are also significant (p = 0.01145).
Temperature has significant effects on nectar concentration (p = 0.000). Interaction of relative humidity, time and layers has
significant effects on nectar concentration (p = 0.0024012). Oldest plants had highest concentration of 10.1 w/w morning and
afternoon 36.5 w/w at 4:00 PM for whereas medium plants had nectar concentration of 5.7 w/w morning and afternoon 16.7
w/w and the smaller or younger plants had nectar concentration of 2.7 w/w morning and afternoon 9.1 w/w and this shows
age has a significant effect on nectar concentration and volume. Conclude that future temperature rise could have negative
effect on the nectar production since for croton also no nectar could be collected at peak temperature of 30°C and no nectar
recreation after this peak temperature that indicates climate change can increase temperature which will have negative
influences for honey production in the future unless we combat against climate change which will affects honey production
and productivity for the country and we will lose honey and its medicinal values of honey also.
KEYWORDS
Croton macrostachyus; Environmental factors; Plants age; Nectar concentration; Nectar volume
INTRODUCTION
C. macrostachyus Hochst. ex Delile, known as broad-
leaved called croton in English and named by various
vernacular names in the different areas of Ethiopia [1]. C.
macrostachyus Hochst. ex Delile is a species of the genus
Croton. Euphorbiaceae family, commonly known as the
spurge family [2]. Croton macrostachyus occurs as a
pioneer species commonly on degraded mountain slopes,
on disturbed areas, in borders of cultivated fields, on
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waste ground, along river habitats at altitudes between
1,100 and 2,500 m. a. s. l [3]. The response of nectar
secretion to external environment and variation in nectar
traits associated with intrinsic plant characteristics [4].
Nectar secretion is strongly influenced by plant age [5].
Plants’ ability to sense their environment and respond to
it is critical for their survival [6].
The contribution of a bee plant species to honey
production depends on the plant’s nectar secretion quality
and quantity, which is mainly governed by biotic and
abiotic factors [7]. Volume and concentration of nectar
vary among plant species and different varieties of the
same species may also differ greatly in nectar sugar
concentration [8]. The species of bee, colony within
species, month of year and the time of day when the nectar
collected all have a significant effect on the sugar
concentration of collected nectar [9].
Watery exudation from plants accumulates when
atmospheric humidity is high, and evaporation thereby is
retarded. This can easily be demonstrated in connection
with bleeding from several tissues [10]. A significant
effect of temperature was found on nectar secretion, with
a negative effect of very high temperatures in all species
[11]. The east African highland Musa cultivars having the
highest nectar volume have the lowest sugar
concentration, while the dessert types with the least nectar
volumes have the highest sugar content [12]. Decreased
soil moisture significantly reduced the leaf relative water
content [13]. It is a general assumption amongst plant
physiologists and Ecologists that stomata have evolved to
provide a Controlling water loss from plants while
allowing photosynthesis [14]. Daylight time has
significant effects on nectar volume and concentrations of
Callistemon citrinus L [15].
Volume and concentration tend to show more differences
with respect to time of day [16]. The other revealed that
there was great variability in nectar production, and it is
evident that higher nectar production occurred at high
humidity and low temperature [17]. Differences in
microclimate can also lead to variation observed between
populations at different habitats [18]. The accumulation of
sugar in and near the flower under the influence of low
temperatures and increasing permeability of the plasma
membrane under the influence of high temperature [19].
It was compared that the changes in nectar secretion under
temperatures expected by the end of the century and
estimated the effect of climate warming on nectar
secretion of plants flowering in different seasons and of
very high temperatures has negative effects in all species
[11]. When humidity increases, the secretion of water, but
not that of sugar, from nectaries is increased and excessive
water supply lessens the sugar surplus in the parts of the
flower and nectar is more diluted when humidity is high
[15].
Watery exudation from plants accumulates when
atmospheric humidity is high, and evaporation thereby is
retarded. This can easily be demonstrated in connection
with bleeding from several tissues [19]. Nectar is more
diluted when humidity is high, and honey that is stored at
such times is likely to be high in water content [19]. The
drier microclimate at the border of the sessile oak-
hornbeam and sessile oak-Turkey oak woods in site 3 may
stand in the background of large amounts of concentrated
nectar even in isolated flowers [18].
MATERIALS AND METHOD
Description of the Study Area
Hawassa is a city in Ethiopia, on the shores of Lake
Hawassa in the Valley. It is located 273 km south of Addis
Ababa. It has latitude and longitude of 7°3′N 38°28′E
7°3′N 38°28′E and an elevation of 1708 meters above sea
level. Hawassa has a tropical savanna climate though it
borders on a subtropical highland climate
(www.hu.edu.et) Background of Hawassa University
October 2, 2013.The extra cloudiness of the wet season is
sufficient to make it substantially cooler than the dry
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season despite a higher sun angle; however, the coolest
morning temperatures, often close to freezing, occur
during the dry season.
Experimental Design and Sample Size of the
Experiment
Maximum variation purposive sampling techniques were
used to select trees based on their age. Each plant was
categorized into three layers (layer one is bottom layer,
layer two is medium and layer three is top layer for oldest,
medium, and youngest plants leveled similarly) for the
experiments. Inflorescences were selected randomly but
flower heads were selected purposively. The idea behind
Maximum variation sampling is to look at a subject from
all available angles, thereby achieving a greater
understanding [20]. Nine trees with each replication for
three ages of plants proposed for experiments or three
oldest trees, three medium trees and three youngest trees
and three layers were taken for experiment from each tree
= 3 × 9 = 27.
Collection and Measuring of Nectar Volume and
Concentration
Nectar volume and concentration were taken and
measured from all three layers of the trees and four flower
heads were taken from each layer of trees from all ages.
Each sample flower represented separate layers of the
trees. Nectar volume was measured after collected by
micropipette tips and brought to laboratory.
Collection of Soil Sample and Measuring its Moisture
Contents
Soil samples were collected from the area of oldest,
medium, and youngest plants of C. macrostachyus
Hochst. ex Delile and their weight were measured by
sensitive balance. Dry weight was measured after oven
dry and then the difference of freshly weight taken and
oven dry weight gave us soil moisture contents to see its
effects on nectar volume and concentrations and
repeatedly measured by soil Ph and moisture tester
directly and soil was taken from the under the area of these
trees from four spots of an individual trees at the depth of
25 cm for these three ages.
Selection of Trees based on their Age and Caging their
Inflorescences for Nectar Collections
Nine trees of C. macrostachyus Hochst. ex Delile were
selected; three oldest, three medium and three youngest
plants and then their age of inflorescences was determined
based on maximum variation purposive sampling
methods and then their nectar were collected and
measured. Nectar was measured from four flower heads
of each layer after inflorescences were selected randomly
for each layer (upper layer, medium and bottom layers or
lower layers) in the morning and afternoon to evaluate
time effects on nectar concentration and volume. Nectar
sugar concentration in the nectar produced per flower was
measured in the field (as sucrose equivalent) using a hand
refractometer (American Optical 10431, Buffalo, NY;
range concentration 0-45, BRIX units, at the time of peak
nectar secretion in the day, as sucrose equivalent [8].
Sugar concentration and nectar volume were quantified
[6].
Data Compilation and Analysis
Sequences of steps were used: First, all plants in a
population were counted, samples were selected and
sampled. After sampling, data were inserted to computer
Microsoft excel 2010 and imported to R software version
3.44. Multilevel analysis was used to see interaction
between variables affecting nectar volume and
concentration of C. macrostachyus. Anova was used to
seeing the significance of these variables on nectar
volume and concentration.
RESULTS AND DISCUSSION
The interaction of nectar volume, soil moisture and nectar
concentration of C. macrostachyus indicated that medium
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plants taken from the area of soil moisture of 30.4% had
moderate nectar concentration of 27.2% and youngest
plants taken from the area of soil of 62.4% had lower
nectar concentration of 16.7% Oldest plants taken from
the area of soil moisture of 27.29% had highest nectar
concentrations 36.5% this infers effect of soil moisture is
significant on nectar concentration (p = 0.000). Effects of
nectar concentration is significant on nectar volume (p =
0.000). Interaction of soil moisture and nectar
concentration has no significant (p >0.05) effects on
nectar volume When nectar concentration increases,
nectar volume decreased. This finding is in line with the
finding of [12] (Figure 1).
Figure 1: Interaction of nectar volume, soil moisture
and nectar concentration of C. macrostachyus Hochst. ex
Delile.
The effect of daylight time is significant on nectar
concentration (p = 0.000) and effects of trees layers is
significant on nectar concentration (p = 0.000) (Figure 2).
Interaction of daylight time and trees layers has no
significant effects on nectar concentration with p >0.05.
Nectar concentration increased in the afternoon for the
oldest, medium, and youngest age of C. macrostachyus.
This infers the age of plants and daylight time determined
nectar volume and concentrations. A similar finding was
reported that nectar secretion dynamics generally
indicated an increasing trend early in the morning,
peaking toward midday, but different species observed to
have different peak nectar secretion times [7].
Figure 2: Interaction of trees layers, daylight time and
nectar concentration of C. macrostachyus Hochst. ex
Delile.
The interaction among relative humidity, daylight time
and nectar volume of croton indicated that daylight time
and relative humidity affected nectar volume as shown
below (Figure 3). The effect of relative humidity is
significant on nectar volume (p = 0.000). An effect of
daylight time is not significant on nectar volume (p >0.05)
and interaction of relative humidity and daylight time has
no significant effects on nectar volume (p >0.05). A nectar
volume was higher in the morning than in the afternoon
for all three-age categories at the time where relative
humidity was higher. This speculation in the morning
more humidity is found in the air that increases nectar
volume. Nectar volume was lower in the afternoon at time
relative humidity decreased that might be due to reduction
of relative humidity because increment of evaporation in
afternoon than in the morning since temperature increases.
Figure 3: Interaction of relative humidity, daylight time
and nectar volume of C. macrostachyus Hochst. ex
Delile.
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Relative humidity has significant effects on nectar
concentrations (p = 0.000) and daylight time has
significant effect on nectar concentration with (p = 0.000)
(Figure 4). Nectar concentration was lower at the time
relative humidity was higher in the morning, but in the
afternoon nectar, concentration was higher at the time
relative humidity was lower which means relative
humidity and nectar concentrations are inversely
comparative to each other. Interaction of daylight time
and relative humidity has significant effects on nectar
concentration with p = 0.0001 and this result is parallel to
reports on Callistemon citrinus L [15].
Figure 4: Interaction of relative humidity, time, and
nectar concentration of C. macrostachyus Hochst. ex
Delile.
Figure 5 below shows interactions of temperature,
daylight time and nectar concentrations of Croton
macrostachyus. Temperature has significant effects on
nectar concentration with (p = 0.000) and daylight time
has significant effect on nectar concentration with (p =
0.0098631) and their interactions has also significant
effect on nectar concentrations with (p = 0.0008304). In
the afternoon, nectar concentration increased. This
implies daylight time has a significant effect on nectar
concentrations due to increment in temperature in the
afternoon. Nectar concentration was lower in the morning
than in the afternoon. Similarly, it was reported that there
was an increasing concentration during the day as
temperature increases with corresponding decrease in
relative humidity [17].
Figure 5: Interaction of temperature, daylight time and
nectar concentration of C. macrostachyus Hochst. ex
Delile.
Figure 6 below shows interactions of temperature,
daylight time and nectar volume of Croton
macrostachyus. Temperature has significant effects on
nectar volume (p = 0.0002499). Daylight time has no
significant effects on nectar volume (p >0.05) and their
interaction has also no significant with (p >0.05). In the
afternoon, nectar volume decreased which means that
daylight time has an effect on nectar volume due to higher
temperature in the afternoon that decreased nectar
volume. Similarly, reported that the volume of nectar in
both Melliferous plant species was high in the early hours
of the day [17]. This implies nectar volume is affected by
daylight time for different species also that might be due
to temperature increment in afternoon than in the morning
hours of the day.
Figure 6: Interaction of temperature, daylight time and
nectar volume of C. macrostachyus Hochst. ex Delile.
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Temperature and soil moisture have significant effects on
nectar volume (p = 0.00016 and 0.0000) respectively, and
their interactions have also significant effects with (p =
0.0005800) (Figure 7). Age and relative humidity have
significant effects with (p = 0.000 and 0.000) respectively
and their interaction has significant effects with (p =
0.0003717). Time has no significant effects on nectar
volume with (p >0.05), but age has significant effects on
volume (p = 0.000), but their interaction has significant on
volume with p value of (p = 0.006993). This is in line with
the finding that demonstrated with defoliation
experiments conducted on Impatiens glandulifera that
only a fraction of the day’s nectar secretion depends on
the day’s photosynthesis [5].
Figure 7: Interaction of nectar volume and
concentration (%) of three age categories of plants in the
morning with temperature, relative humidity, and soil
moisture and tree layers.
Age, relative humidity, and daylight time have significant
effects with (p = 0.000, 0.000 and 0.0003643) respectively
and their interaction has significant effects with (p =
0.0004939) (Figure 8). Interactions of age and layers of
trees have significant effects with (p = 0.007700).
Interaction of daylight time and relative humidity has
significant effects with (p = 0.0002). Interaction of age
and daylight time has significant effects with (p = 0.000).
This deduces age and daylight time has significant effects
on nectar volume and youngest age produced more nectar
volume than medium and oldest age that might be due to
bleeding of water from several tissues of youngest than
others. Daylight time, relative humidity and layers of trees
have significant effects on nectar concentration with (p =
0.0003643, 0.000 and 0.000) respectively and their
interactions have significant effects on nectar
concentration (p = 0.0024012). Interaction of temperature,
age, layers and daylight time has significant effects with
(p = 0.041298). The highest nectar volume had the lowest
sugar concentration, and this finding is in line with the
finding of [12].
Figure 8: Interaction of nectar volume and
concentration (%) of three plant age categories in the
afternoon with soil moisture, temperature, relative
humidity and tree layers.
CONCLUSION
Nectar concentrations and volume of medium and oldest
age of C. macrostachyus was affected by age of plants,
daylight time, relative humidity, temperature, layers of
trees and soil moisture, but for youngest plants nectar
volume was not affected by relative humidity and nectar
concentration was not affected by temperature. Youngest,
medium, and oldest ages had nectar concentrations of 9.1
w/w, 16.7 w/w and 36.5 w/w respectively in the afternoon
and in the morning 2.7 w/w, 5.7 w/w and 10.1 w/w
respectively. Conclude that future temperature rise could
have negative effect on the nectar production of plant
species, since for Croton also maximum temperature to
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produce nectar was 30°C and above this temperature no
nectar production was seen and may have negative effects
on honey productions since nectar quality will be lost if
climate changes since temperature rises and that can cause
a loose of volatile compounds found in nectar those
determine quality of nectar as well honey since for quality
honey quality nectar is necessary. For three ages of C.
macrostachyus lower layers recorded lower nectar
concentration and higher nectar volume when compared
to the medium and top layers of the trees in the morning.
In the afternoon higher nectar concentration and lower
nectar volume was recorded in the top layer than the
medium and lower layers of the trees [21].
ACKNOWLEDGEMENT
First and foremost, I am grateful to acknowledge my
advisors Dr. Getachew Sime and Dr. Zufan Bedewi for
his/her supervision, critical comments, suggestion,
valuable time spent with me in the laboratory and field
work and devoted their time to add essential points to
improve the quality of my research paper. It is my
privilege to acknowledge Dr. Beyene Dobo and Mosisa
Daba for their assistance during laboratory work; and Dr.
Feto Esmo general director of Oromia research institute
for his help in teaching me R software that helped me to
analysis my data.
AVAILABILITY OF DATA AND MATERIALS
The data sets analyzed during the current study are
available.
COMPETING INTERESTS
The authors declare that they have no competing interests.
AUTHORS' CONTRIBUTIONS
All authors read and approved the final manuscript for
publications.
FUNDING
The Thesis was funded by Oromia agricultural research
institute and paper is from my thesis parts for publications.
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