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Transpiration in Leaves Experiment

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Introduction

EXPERIMENT DATE TOPIC AIM APPARATUS PROCEDURE #1 19-0CTOBER-2011 Transpiration To investigate the effects of certain factors on the rate of transpiration. Leaves with petiole, electric balance, stopwatch, retort stands, string, fan, Vaseline, pin, polystyrene cement, paper clips, microscope, anhydrous cobalt chloride paper 1. Several leaves with petiole intact were removed from a plant. The leaves were strung together and weighed, with an attempt being made to get a mass of just about 10g. 2. The time was noted and the leaves hung in such a way so as to not touch one another under 3 conditions: still air, turbulent air from a fan and with both leaf surfaces smeared with Vaseline. 3. The leaves were reweighed at 15 minute intervals for 4 more readings. 4. The percentage decrease in weight at each interval was calculated using the formula: percentage decrease= [(a-b)*100]/a where a=initial weight at the beginning of the experiment b=new weight 1. A strip of anhydrous cobalt chloride paper was applied to the upper and lower surfaces of and intact leafy shoot. ...read more.

Middle

63.6 63.6 63.6 63.6 63.6 63.6 Amount per unit area(no./mm2) 7.86 7.55 7.86 12.58 14.15 14.15 When cobalt chloride was used on the leaves, the upper surfaces changed the blue paper to pink at a slower rate than the lower surface did. CALCULATIONS Percentage change A For A between 0 and 15 min =[ (10.50-10.24)*100]/10.50 =2.48% Between 15 and 30 min =1.37% Between 30 and 45 mins= 2.60% Between 45 and 60 min= 3.59% Overall % change= 10.04% Percentage change B For B between 0 and 15 min= [(10.25-9.95)*100]/10.25 = 2.92% Between 15 and 30 min=1.01% Between 30 and 45 mins=0.91% Between 45 and 60 min= 0.62% Overall % change= 5.46% Percentage change C For C between 0 and 15 min= [(11.93-11.91)*100]/11.93 = 0.12% Between 15 and 30 min=1.01% Between 30 and 45 min=1.27% Between 45 and 60 min= 0.52% Overall % change= 2.92% Area= ?r2 r=9mm hence area= 63.6mm2 DISCUSSION CONCLUSION Transpiration is the evaporation of water from the leaves of plant. The rate of transpiration is not constant. ...read more.

Conclusion

The percentage change when Vaseline was present was however lesser than that without vaseline as expected. The vaseline served as a cuticle size increaser and hence prevented too much water from escaping from the plant leaves hence, the percentage change in mass was smaller. As seen by the experiment, increasing the number of stomata increases the level of transpiration and hence the level of water loss. This was demonstrated in the relatively quick time taken for the blue cobalt chloride paper to become pink when place on the lower surface which had a greater number of stomata in comparison to the time taken to change on the upper surface which was proven to have less stomata. The problems in the experiment which caused the deviation in results could be due to improper use of the equipment. Due to the reduction in forces pushing up the water to replace that evaporated, the inconsistent results obtained for the turbulent wind system could have been due to such. Transpiration of water from the leaves of plants is affected by several factors including cuticle thickness, presence of wind and number of stomata as demonstrated in this experiment. The systems can either reduce or increase the transpiration rate. ...read more.

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