The Middle East region has arid and semi-arid climatic conditions that are characterised by water scarcity and high temperatures that result in high evaporation rates (Dubreuil et al., 2013; Voss et al., 2013; Beaumont, Blake & Wagstaff 2016). Additionally, the loose soils and desert winds contribute to air pollution when the soil is blown into the air leading to respiratory illnesses (Anderson et al. 2012; Lelieveld et al. 2014). The loose soils are also prone to soil erosion leading to the loss of soil nutrients (Anderson 2013; Farhan, Zregat & Farhan 2013). Increasing plant cover is reported the most viable solution to the problem of soil erosion and air pollution by soil (Berendse et al. 2015; Ochoa et al. 2016). However, given the issue of water scarcity, finding plant species that can thrive with minimum water requirements is essential. In the UAE, groundwater comprises 51% of the overall water supply and is commonly used for the irrigation of agricultural, forestry, and landscaping plants. Purified water accounts for 37% of the water reserve and is mainly used for domestic purposes.
The other 12% of water is obtained by recycling processes and is mostly used for landscaping irrigation (Gonzalez et al., 2014). This report shows that a substantial portion of water is used in irrigation of garden plants whose main purpose is landscaping. Therefore, this investigation seeks to find the most suitable plant that can thrive with minimal water requirements to survive the harsh climatic conditions of the Middle East. The findings of this study will determine which garden plant is capable of growing satisfactorily with limited water requirements to survive in the arid and semi-arid climatic conditions of the Middle East. The identification of such a plant will promote its growth in the UAE using the limited water resources, which will not only conserve the soil and its nutrients but will also protect the society from respiratory disorders associated with inhaling soil particles in the air.
It is hypothesized that the sunflower plant (Helianthus annuus) would grow fastest and have the highest biomass. Helianthus annuus is a popular garden plant of significant economic and aesthetic importance. Additionally, it has been shown to be economic in terms of usage of resources due to its fast growth rate (Brouillette et al. 2014; SFGATES 2016).
The independent variable was the type of garden plant, which included five species: Zinnia (Zinnia elegans), Cosmos (Cosmos bipinnatus), Sunflowers (Helianthus annuus), Dahlias (Dahlia pinnata), and Vinca (Vinca diformis). Different garden plants have varying water requirements depending on their inherent adaptations to survive under varying climatic conditions.
The dependent variable was the increase in biomass, which was measured in grams. An increase in biomass is a useful indicator of the rate of plant growth, which in turn shows the growth conditions that favour the development of the plant. An increase in biomass was measured consistently using the biomass (dry weight) of the seeds at the beginning of the experiment and the biomass of the plants at the end of the experiment.
|Variable||How it was controlled|
|Water||Using a constant volume of 300 ml per day per plant, which was attained using a measuring cup.|
|Soil type||The same soil type was used for all the plants.|
|Soil mass||A constant mass of soil as used in all the pots.|
|Soil fertility||The fertility of the soil was kept constant as no fertilizer was applied to all the plants.|
|The moisture content of final product||The plants were dried in an oven until no further change in mass was observed.|
|Variable||How it was controlled|
|Sunlight||Plants grew under similar sunlight conditions|
|Concentration of carbon dioxide||Plants grew under similar sunlight conditions|
Apparatus and Materials
- 5 types of plant seeds: Zinnia (Zinnia elegans), Cosmos (Cosmos bipinnatus), Sunflowers (Helianthus annuus), Dahlias (Dahlia pinnata), and Vinca (Vinca diformis)
- 300 ml of water
- Weighing scale
- Measuring cup
- 25 Pots
- Aluminium foil
- Two trays
- Measure the appropriate amount of soil in accordance to your pots.
- Measure and record the mass of every seed.
- Place five seeds of one plant species in every five pots (one in each).
- Water the plants once a day with 300 ml of water for 30 days.
- After 30 days, harvest the plants and wash them.
- Set the temperature of an oven to 60 degrees.
- Place the plants on a tray and keep them in the oven for six hours.
- After six hours, remove them and measure their mass.
- Ensure that the mass is stabilized by putting the plants back in the oven and reweigh them.
- Record your results.
Justification of Method Used
Five seeds from each plant type were used to provide replicates and increase the validity of the results. The use of replicates helps to ascertain the reproducibility and validity of the experiment by confirming that the observed results are not due to chance occurrences. Additionally, using replicates makes it possible to apply statistical methods of data analysis and ensure that the findings are generalizable to the population. The plants were grown in a field after which the biomass data was collected in the laboratory. The amount of data collected was sufficient because a good number of garden plant species were compared with adequate replication of the biomass measurements. This experiment was a fair test because all plants were accorded similar treatment regarding the volume of water during growth as well as other growth conditions including the mass and type of soil, sunlight, carbon dioxide concentration, and soil fertility (no fertilizer as added to all plant groups). Additionally, the processing of the plants to obtain the final biomass was done uniformly.
Risk Assessment and Ethical Considerations
No additional chemicals (such as fertilizers), which could contain substances known to have deleterious health effects, were used in the process. However, proper standards of handling and disposing of plants were followed throughout and after the experiment.
Data Collection, Processing, and Presentation
Table 1: The biomass of the five plant species and the mean biomass for each species
|Sunflower (Helianthusannuus)||Zinnia (Zinniaelegans)||Cosmo (Cosmosbipinnatus)||Dahlia (Dahliapinnata)||Vinca (Vincadiformis)|
|Trial 1 (±0.01 g)||0.15||2.69||0.02||0.03||0.02|
|Trial 2 (±0.01 g)||0.11||2.10||0.02||0.04||0.03|
|Trial 3 (±0.01 g)||0.10||1.36||0.02||0.01||0.03|
|Trial 4 (±0.01 g)||0.19||1.63||0.02||0.03||0.03|
|Trial 5 (±0.01 g)||0.12||1.27||0.03||0.02||0.02|
|Mean increase in Biomass (g) (±0.01 g)||0.13||1.81||0.02||0.03||0.03|
The mean increase in biomass for the five species=0.40
It was observed that Zinnia elegans grew bigger than the other plants followed by Helianthus annuus. The physical sizes of the three other species (Cosmos bipinnatus, Dahlia pinnata, and Vinca diformis) could not be easily distinguished visually.
The mean was calculated using the formula: Mean= Sum/Count.
For example, for Sunflower (Helianthus annuus), Mean = (0.15+0.11+0.10+0.19+0.12)/5 =0.67/5 =0.134 =0.13
For example, the mean for Sunflower (Helianthus annuus) was 0.13 while the overall average was 0.40.
The (xi-u)2 function for Sunflower is calculated as (0.13-0.40)2= (-0.27)2 or 0.0729. Following the same procedure for Zinnia, Cosmo, Dahlia and Vinca, the values are 1.9881, 0.1444, 0.1369, 0.1369.
= 0.0729+1.9881+0.1444+0.1369+0.1369 = 2.4792
Variance = 2.4792/5 = 0.49584
Standard deviation = √Variance = √0.49584 = 0.7041 = 0.70
Graphs and Charts
The plant growth rate of the plants was highest in Zinnia elegans (1.81g) followed by Helianthus annuus (0.13g). The lowest growth rate was observed in Cosmos bipinnatus (0.02g). Dahlia pinnata and Vinca diformis had the same growth rate of 0.03g. The findings did not support the hypothesis that sunflower (Helianthus annuus) would have the highest growth rate despite the presence of sufficient literature showing that Helianthus annuus was among fast-growing garden plants (Broillette et al. 2014). The differences in growth rates as indicated by the differences in means and the large standard deviation from the main mean showed that the differences in water efficiency were significant. Plants require water for evapotranspiration; they use their roots to absorb water from the soil and eliminate it through the leaves and stems through the process of transpiration (Dubreuil et al. 2013). In addition, water has the tendency to escape from open surfaces through the process of evaporation, which occurs in plants from the soil and exposed plant surfaces such as the stem and leaves (Ochoa et al. 2016). The crop water needs are determined by the climate, type of crop, and stage of growth (Elliot et al. 2014).
In this study, the climate and stages of growth were kept constant indicating that the observed differences in the increase in biomass were due to the type of crop, which in turn corresponded to the drought resistance capacity of the plants because all climatic conditions were kept constant. These results showed that the data obtained were reliable. The ability of Zinnia elegans to grow satisfactorily using a limited volume of water showed that it was the best candidate to be used as a cover crop for landscaping purposes to prevent soil erosion in the UAE without expending vast water resources (Escalona et al. 2014). Zinnia elegans is native to dry lands of the Southern parts of America (Chicago Botanic Garden 2016). Studies show that this species is also suitable for vertical gardens and green roofs due to its efficient water usage (Escalona et al. 2014). The second best candidate for cover crop plants was Helianthus annuus. However, Cosmos bipinnatus, Dahlia pinnata, and Vinca diformis were not suitable plants because they exhibited limited growth as marked by the small increase in biomass under similar conditions.
Zinnia elegans had the highest growth rate and minimal water requirements of the five plants with a mean increase in biomass of 1.81g followed by the sunflower plant (Helianthus annuus) with a mean increase in biomass of 0.13g. Dahlia pinnata and Vinca diformis were third with an increase in biomass of 0.03g while Cosmos bipinnatus had the lowest growth rate (a mean increase in biomass of 0.02g). These findings point to the conclusion that Zinnia elegans had the best growth rate in terms of increase in biomass at a minimum daily water supply of 300 ml per day and was best suited for use as a cover crop in areas with limited water resources.
Evaluation of Method Used
The method was reliable because related plants were used to reduce the variations of plant water needs that occurred in different plants. The replication of the groups also increased the validity of the study by ensuring that the findings were not merely due to chance. However, the effects of temperature, humidity and wind speed on the water needs of plants were not considered, which could have increased the water deficit as high temperatures, low humidity and high wind speeds are known to aggravate water loss through evapotranspiration (Ochoa et al. 2016). The experiment could be improved by growing the plants at varying wind speed, humidity levels, and temperatures and determining how these changes affect plant water needs. Future studies could look into the exact water needs of the plants by growing the seeds with varying water quantities to determine the lowest amount of water that supports the satisfactory growth of the plants. The sample size was appropriate for the study because it allowed for the replication of the findings. However, future studies could increase the replicates further to enhance the validity of the study.
From the findings of the investigation, Zinnia elegans is best suited to growing in warm climatic conditions. Therefore, this plant can be grown to provide plant cover, minimise soil erosion and air pollution. The advantage of growing Zinnia elegans for plant cover is that a high rate of growth is observed with minimal water input due to the heat and drought tolerance of the plant (Chicago Botanic Garden 2016). The plant is also low maintenance thus does not require extensive resources. However, the downside of using Zinnia elegans for cover plants is that it affected by excess water, which leads to the development of a disease called powdery mildew.
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