rav65819_ch38_757-772

rav65819_ch38_757-772 - ;;;;;;;; chapter 38 Transport in...

Info iconThis preview shows pages 1–5. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: ;;;;;;;; chapter 38 Transport in Plants introduction TERRESTRIAL PLANTS FACE TWO major challenges: maintaining water and nutrient balance, and providing sufficient structural support for upright growth. The vascular system transports water, minerals, and organic molecules over great distances. Whereas the secondary growth of vascular tissue allows trees to achieve great heights, water balance alone keeps herbaceous plants upright. Think of a plant cell as a water balloon pressing against the insides of a soft-sided box, with many other balloon/box cells stacked on top. If the balloon springs a leak, the support is gone, and the box can collapse. How water, minerals, and organic molecules move between the roots and shoots of small and tall plants is the topic of this chapter. concept outline 38.1 Transport Mechanisms Local changes result in long-distance movement of materials Water potential regulates movement of water through the plant Aquaporins enhance osmosis A water potential gradient from roots to shoots enables transport 38.2 Water and Mineral Absorption Three transport routes exist through cells Transport through the endodermis is selective 38.3 Xylem Transport Root pressure is present even when transpiration is not occurring Vessels and tracheids accommodate bulk ow 38.4 The Rate of Transpiration Stomata open and close to balance H 2 O and CO 2 needs Turgor pressure in guard cells causes stomata to open and close Environmental factors affect transpiration rates 38.5 Water-Stress Responses Plant adaptations to drought include strategies to limit water loss Plant responses to ooding include short-term hormonal changes and long-term adaptations Plant adaptations to high salt concentration include elimination methods 38.6 Phloem Transport Organic molecules are transported up and down the plant Turgor pressure differences drive phloem transport 757 rav65819_ch38_757-772.indd 757 rav65819_ch38_757-772.indd 757 12/7/06 6:53:51 PM 12/7/06 6:53:51 PM 38.1 Transport Mechanisms How does water get from the roots to the top of a 10-storyhigh tree? Throughout human existence, curious people have wondered about this question. Plants lack muscle tissue or a circula-tory system like animals have to pump fluid throughout a plants body. Nevertheless, water moves through the cell wall spaces between the protoplasts of cells, through plasmodesmata (connections between cells), through plasma membranes, and through the interconnected, conducting elements extending throughout a plant (figure 38.1). Water first enters the roots and then moves to the xylem, the innermost vascular tissue of plants. Water rises through the xylem because of a combination of factors, and some of that water exits through the stomata in the leaves (figure 38.2)....
View Full Document

Page1 / 157

rav65819_ch38_757-772 - ;;;;;;;; chapter 38 Transport in...

This preview shows document pages 1 - 5. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online