Biology - 0610 CIE

Transpiration

Gbogbo ọrọ náà

On a hot day a single tree can pull hundreds of litres of water up from its roots to its leaves, where most of it simply evaporates away. This loss of water vapour, transpiration, is the engine that drives water all the way up a plant, with no pump at all.

In this lesson you will learn what transpiration is, how temperature and wind speed change its rate, and how to measure it. Extended students will explain the transpiration pull that lifts water up tall trees, how leaf structure and stomata control water loss, and why a short of water makes a plant wilt.

Ebumnobi

Describe transpiration as the loss of water vapour from leaves
State that water evaporates from the surfaces of the mesophyll cells into the air spaces and then diffuses out of the leaves through the stomata as water vapour
Investigate and describe the effects of variation of temperature and wind speed on transpiration rate
[Supplement] Explain how water vapour loss is related to: the large internal surface area provided by the interconnecting air spaces between mesophyll cells and the size and number of stomata
[Supplement] Explain the mechanism by which water moves upwards in the xylem in terms of a transpiration pull that draws up a column of water molecules, held together by forces of attraction between water molecules
[Supplement] Explain the effects on the rate of transpiration of varying the following factors: temperature, wind speed and humidity
[Supplement] Explain how and why wilting occurs

Akọmọ Ojú-ẹkọ

Transpiration explains how water reaches the top of the tallest tree, why plants wilt in the heat, and why a windy day dries out a garden. It links osmosis, diffusion, leaf structure and xylem into one story, and it is tested both as recall and as data and graph interpretation.

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Ayẹwo Ẹkọ

Ekele diri gi maka imecha ihe karịrị na Transpiration. Ugbu a na ị na-enyochakwa isi echiche na echiche ndị dị mkpa, ọ bụ oge iji nwalee ihe ị ma. Ngwa a na-enye ụdị ajụjụ ọmụmụ dị iche iche emebere iji kwado nghọta gị wee nyere gị aka ịmata otú ị ghọtara ihe ndị a kụziri.

Ị ga-ahụ ngwakọta nke ụdị ajụjụ dị iche iche, gụnyere ajụjụ chọrọ ịhọrọ otu n’ime ọtụtụ azịza, ajụjụ chọrọ mkpirisi azịza, na ajụjụ ede ede. A na-arụpụta ajụjụ ọ bụla nke ọma iji nwalee akụkụ dị iche iche nke ihe ọmụma gị na nkà nke ịtụgharị uche.

Jiri akụkụ a nke nyocha ka ohere iji kụziere ihe ị matara banyere isiokwu ahụ ma chọpụta ebe ọ bụla ị nwere ike ịchọ ọmụmụ ihe ọzọ. Ekwela ka nsogbu ọ bụla ị na-eche ihu mee ka ị daa mba; kama, lee ha anya dị ka ohere maka ịzụlite onwe gị na imeziwanye.

Transpiration is best defined as the: A. uptake of water by roots B. loss of water vapour from leaves C. movement of sugar in phloem D. loss of mineral ions Answer: B
Which change increases the rate of transpiration? A. higher humidity B. lower temperature C. higher wind speed D. still air Answer: C
Water vapour leaves the leaf mainly through the: A. xylem B. stomata C. cuticle D. phloem Answer: B
[Supplement] The water column in the xylem does not break because of: A. active transport B. cohesion between water molecules C. lignin pumping water D. osmosis in the leaf Answer: B
A potometer bubble moves 60 mm in 5 minutes. The rate of uptake is: A. 5 mm/min B. 12 mm/min C. 60 mm/min D. 300 mm/min Answer: B