August 15, 2017 | Author: JeemCarloFagelaPula | Category: Organic Compounds, Plant Stem, Plants, Root, Chemical Compounds
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Gross Composition of Plants (Synedrella nodiflora)

Jeem Carlo F. Pula, BS Biology

Plant Physiology Lab

1st of July 2015

Introduction Different parts possess by plants has its own role and is important in performing processes that supports their growth and development. However, these structures will not function and develop without the organic and inorganic compounds. Inorganic compounds, which are present mostly in the environment, are being used by plants to produce organic compounds through biochemical processes. These organic and inorganic compounds, which comprises a plant, can be determined if its structures are broken down into its chemical components. Just like in humans, water is the most abundant inorganic compound which comprises a plant. This inorganic compound is one of the most significant substances helping in the delivery and transport of nutrients from the root to the different parts of a plant. Since water constitutes most of the plant, it can be determined through the process of drying. The loss of water can be measured by the difference between the fresh weight and dry weight of the plant. The dry weight is usually taken as the basis for expressing results of chemical analysis rather than fresh weight because of the variability of the water content in plant tissues (Alejar, 2013). Once the plant has dried, inorganic elements will remain if the plant is subjected to a process known as combustion. This process turns the dried plant into ashes and further into gray-white colored ashes. During this process, the organic compounds such as lipids, carbohydrates, proteins, and nucleic acids changed into gaseous forms like water and carbon dioxide. Also, the remains in the ash are inorganic elements and minerals which are in the form of oxides.

Objectives This experiment aims to help in familiarizing the methods commonly used in determining the moisture, dry matter, organic matter, and ash contents of plant tissue samples. Moreover, the products and collected samples that yielded from this experiment should be used in the next experiment.

Materials and Methodology The experiment for the gross composition of plants was done in three parts: preparation of the plant materials, combustion/ dry ashing, and calculation of percentage for water, dry matter, ash, and organic matter. Prior to the experiment, the specimen were collected. Dead, damaged leaves and adhering soil particles were removed. It was then put for three days in the oven at 70°C. In the part where the plant materials were prepared, 29 grams of Synedrella nodiflora was weighed by the members of the group. After drying the plant, the members of the group separated the plant organs and weighed 10 grams of leaves and stems, and 4 grams of roots.

Next in the experiment was the combustion and ashing process of the dried plant organs were performed. First is the leaves were burned. The leaves were placed on wire gauze on top of a tripod. With the use of a bunsen burner, the researchers flamed the dried leaves until it turned into ash. It was then stirred by a glass rod until it turned into a grayish white, carbon- free ash. It was left to cool and then placed in a container where it was weighed. The ash weight was determined by getting the difference between the weight of the container plus the ash and the weight of the container alone. To determine the weight of the organic matter, the weight of the ash weight was subtracted to the weight of the dry weight. The same procedure was done for the stems and the roots. The third and last part of the experiment was the computation for the percentage of water, dry matter, ash, and organic matter. The following formulas below were used by the researchers in order to get the result of each. The data and results that were gathered are recorded at Tables 1 and 2. 1)





Freshweight ( FW )−Dry weight ( DW ) x 100 FW

dry matter=


DW x 100 FW

Ash weight( AW ) x 100 FW

organic matter=

DW −AW x 100 FW

Discussion of Results Table 1. The recorded and computed percentage of water, dry matter, ash, and organic matter of Synedrella nodiflora Fresh weight (g) Dry weight (g) Ash weight (g) Organic matter (g) % of water % of dry matter

Leaves 11.67 10 1.97 8.03 14.31 85.69

Stems 11.67 10 0.58 9.42 14.31 85.69

Roots 5.67 4 0.51 3.49 29.45 70.55

Total 29 24 3.06 20.94 -

% of organic matter % of ash









Table 2. The recorded and computed percentage of the whole plant of Synedrella nodiflora. % water of the whole plant % dry matter of the whole plant % organic matter of the whole plant % ash of the whole plant

17.24 82.76 72.21 10.55

Roots Roots make up around one-fourth to one-third of the total dry weight of a plant but it still varies to the age or type of plant. In this case, the plant’s stem and leaves are quite bid but it has a fibrous root. Based on the data given, the fresh weight of the roots used were 5.67 grams, it was supposed to be 10 grams but due to insufficient materials, the required 10 grams was not obtained. After 3 days, the roots dried up and the students weigh it again and learned that the dry weight of the roots is lighter than that of its fresh weight. This happened because the roots’ water composition was lost, the water escapes the roots as water vapor and the roots lost about 26.45% (1.67 grams) water.To compare the dry weight from the ash weight, there was a decrease of61.55 % (3.49 grams) from the weight when it was turned to ash.Its ash weight shows a drastic decrease in weight because their solid compostion such as lipids, carbohydrates, proteins and nucleic acids has been turned into gaseous forms and remains in organic materials in the ash. Organic matter was known by getting the difference of the dry weight and the ash weight. In a 5.67 grams of Synedrella nodiflora, there is an organic matter of 3.49 grams.

Stems According to Evans (1972) the fresh weight depends not just on the conditions of growth but also on the water status at a particular time and place. Based on Virtual Botanic Garden, Synedrella nodiflora is a mesophyte, thus it is a type of terrestrial plant which does not require an environment that is neither strictly dry nor particularly wet so it has a moderate amount of water. Plants are 70% water. It serves as a medium for the conduction and distribution of nutrients and other ions, also water keep the stem from drooping. Based on the results, it shows that the stems consists a 14.31% of water prior to its 11.67 g of fresh weight. During the process of drying, water escapes as water vapor and the remaining mass is the dry matter. The dry matter has a mass of 10 g and has a percentage of 85.69%. After the combustion process, the material turned into a grayish white carbon-free ash. The ash has a weight of 0.58 and has a percentage of 4.97%. The stem, if broken down into their chemical component parts, are roughly made up of organic compounds such as carbohydrates, lipids, nucleic acids, and proteins. Stem has the highest organic matter compared to the leaves and roots. Since Synedrella nodiflora is a dicot stem it is composed of vascular cambium, xylem, phloem and pith. Pith serves as storage of nutrients in the plants.

Leaves In table 1, the computed percentage of the leaves’ water, dry matter, organic matter, and ash is shown. The leaves have the largest ash weight and percentage compared to the roots and stems. This means that there is more ash that can be obtained from leaves even the three of them has the same weight prior to combustion. The stem has more organic matter than leaves which means that organic matter is more abundant in the stem than in leaves. When it comes to the percentage of water and dry matter, the stem and leaves have the same values. In the experiment, there are errors that caused the lack of accuracy in the data that have been gathered. For an instance, there should be a large decrease between the fresh and dry weight of the leaves because, as many scientists have proved, water makes up the 70% of the plant body. Since the plants were dried, there should be a large decrease in the weight because of the loss of water. However, in table 1, only 1.67g was decreased in the weight of the leaves after drying. The major error in this experiment is that the specimen was not weighed while it is fresh, thus, it made the other computations inaccurate compared to the theoretical results.

Figure 1. Formulas used in computing for the % water, dry matter, ash and organic matter of the sample. % water = ((FW - DW) / FW) * 100 % dry matter = (DW / FW) * 100 % ash weight = (AW - FW) * 100 % organic matter = ((DW - AW) / FW) * 100

Plants are known to composed 70% of water in its body, but in this activity, the students came up with only 17.24% which clearly says that they did something that affect their data. The dry matter of the plant is 82.76% of the whole. It is the matter where the water is removed from the plant. After combusting the plant by parts; leaves, stem and roots. Ash weight was obtained, the plant’s ash percentage was 32.29%. The ash contains mostly the inorganic materials which is in minerals that is required by plants as part of their food, to form their structure. And the percentage of organic water was 72.21, which is the organic components that was loss or has been breakdown due to the burning of the sample. These values were obtained by using the formulas given (see figure 1) and the total values in grams of the plant.

Conclusion Summary Study Questions 1. Which is the more reliable basis for expressing results in plant analysis, fresh weight or dry weight? Explain your answer. Dry weight would be a more reliable basis for expressing results in plant analysis rather than fresh weight because of the variability of the water content in plant tissues. In dry weight water was removed and what remains is the dry matter. The dry matter undergoes combustion which results to ash. The ash contains the inorganic components or minerals, in the form of oxides.

2. Based on your results, what proportion of the fresh weight of the plant consists of nutrients absorbed by the roots? As illustrated in table 1, stems and leaves are the proportions of the fresh weight of the plant which is consists of nutrients absorbed by the roots since they have the same weight while they were still fresh. However, as previously stated in the discussion of results, the actual fresh weight of the specimen was not recorded. So the leaves are the proportion of the fresh weight of the plant which must consist of nutrients absorbed by the roots. Leaves are exposed to heat and they are more prone to water loss. So the mechanism of the plant is to supply water or nutrients absorbed by the roots to prevent it from wilting. 3. In the preparation of plant materials (Part A), care must be taken not to press hard on the plant materials. Why? The plant must be pressed flat and dried between sheets of absorbent blotters or semiabsorbent paper such as newspaper. Papers with a glossy surface should be avoided because they are not absorbent enough to aid drying. The plant should be carefully laid out between the drying sheets as their form at this stage largely determines their ultimate appearance. The plant should be press with moderate pressure, preferably an arrangement that will permit as free a circulation of air as possible in order to ensure that the maximum amount of useful information is preserved. Moreover, since the plant materials are fresh, pressing hard might cause the contents of this fresh plant to leak. Also, the plant specimen should be free from damage so that all the parts of the plant (roots, stems, leaves) have equal water loss when it is placed in the oven.


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