Download Determination of the water potential of living plant tissue 2. Objective

1. Title 探究的題目 :
Determination of the water potential of living plant tissue
2. Objective 探究目標 :
Estimate / determine the water potential of potato tissue equivalent to a particular concentration of
sucrose solution. OR
By comparing the change in length / mass of living potato tissue after immersed in sucrose
solution of different concentration, the water potential of a particular sucrose solution that does not
cause change in length / mass of the potato tissue is equivalent to the water potential of the potato
tissuse. OR
To find out the water potential of living potato tissue by immersing it into sucrose solution of
different concentration. OR
Estimate the water potential of fresh potato by immersing in sucrose solution of different
concentration
3. Design principle 設計原理 : An important part to get higher score
Biological principles employed 應用生物學原理 : max. (6)
living cells always has a negative water potential
differentially permeable membrane, (1) allow small molecules to pass through
plant cell wall - rigid, will not burst (1)
Osmosis – net movement of water molecules (1) from region of higher water potential to
lower
Uptake water in hypotonic, turgid (1) cell increase in size/mass
No net movement in isotonic. (1) the size/mass of the potato cells remains unchanged
Loose water in hypertonic, plasmolysis. (1) cell decrease in size/mass
A gradual variation / difference in the degree of tugidity / plasmolysis in medium of
different water potential. (different concentration of sucrose solution) (1)
Linear relationship between the degree of tugidity / plasmolysis and the water potential of
the medium (linear regression) (1)
The “point” (water potential / concentration of sucrose solution) results in no net movement
of water molecule into / out of the cell is the isotonic point which is equivalent to the water
potential of the cell in the experiment. (1)
Assumptions (if applicable) 假定 (如合適) : max. (2)
The potato cells are more or less of the same water potential. (1)
There are difference in the water potential of the cells and the series of sucrose solutions
used. (1)
Change in the size / mass of the potato tuber would be observed due to osmosis. (1)
4. Method and Materials 探究方法（包括所用儀器和材料）:
Briefly describe the method used
Independent variable 改變「獨立變項」的方法
Identify the variable
state how to modify the variable e.g. serial dilution
e.g. Putting the potato tuber into solution of different sucrose concentration
Dependent variable 錄取「應變項」數據的方法
Identify the variable
state how to measure the change of the variable (take readings / data)
e.g. Measure the change in length with a ruler with accuracy up to …
e.g. Measure the change in weight / mass with an electronic balance with accuracy up to …
Controlled variable 控制其他變項
Identify the variables
state how to keep the variables constant throughout the experiment
Minimize evaporation
- tasks completed shiftly to prevent …
- Petri dishes, beaker / paraffin paper covered to prevent …
Identical oth. factors for osmosis
- identical (adequate) immersion period,
- identical submerged surface area
- Potato tubers have been bold dried to prevent …
Miminize errors
- Keep in stable environment e.g. constant room temperature,
- Measuring with great care to up …
5. Procedure 步驟
Logically, concise and precise 合邏輯、簡明、精確 (dummy can follow!)
Point-form in S.I. units 要點形式，以國際單位準確地標示
may divided into several sections 可劃分為不同部分
precautions (if applicable) 預防措施 (如合適)
6. Result 結果
Data table, graphs / charts 數據表，圖線 / 圖表
Briefly describe other observations (if applicable) 簡要描述其他可觀察的變化 (如合適)
e.g.
The change in length/rigidity of the potato tuber in distilled water, 10% sucrose solution and 20%
surcose sulution were recored in the tables below.
Potato tuber in distilled water
Potato
Tuber/disc
Initial
(cm)
Final
(cm)
% Change
Remarks
1
2
3
Average
Potato tuber in 10% sucrose solution
Potato
Tuber
Initial
(cm)
Final
(cm)
% Change
Remarks
1
2
3
Average
Potato tuber in 20% sucrose solution
Potato
Tuber
1
2
3
Average
Initial
(cm)
Final
(cm)
% Change
Remarks
linear regression
線性迴歸
http://en.wikipedia.org/wiki/Linear_regression
http://zh.wikipedia.org/wiki/%E7%B7%9A%E6%80%A7%E5%9B%9E%E6%AD%B8
http://www.ltcconline.net/greenl/courses/201/regression/scatter.htm
Other findings e.g. change in texture, shape, … (if applicable)
The water potential of the potato is equivalent to ?% sucrose solution.
7. Discussion 討論
The most important part to get higher score
Results / Data 結果 / 數據 詮釋
Trend of dependent variable
Controlled variable
Limitation 局限性
Method / equipment / experimental errors
Unusual / anomalous results
Suggestions for improvement and further investigations
Importance and Application
8. Conclusion 結論