Lecture 04/ plant growth

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c. Casparian strip
The Casparian strip is made up of waxy material that is laid down in continuous belts around the endodermal cells surrounding the stele, the vascular tissue of the root. The Casparian strip forms a barrier that blocks water from moving through the cell walls (apoplast).In order for water and dissolved minerals to pass into the stele, they must move through the plasma membrane of the endodermis into the cytoplasmand pass into the vascular cells through plasmadesmata. The plasma membrane provides a selective barrier that helps to keep unwanted material out of the plant. In addition, because the stele is sealed off, water and minerals can't leak back out into the root cortex.

3. Upward mobility
a. Root pressure
Roots pump minerals into the stele. As we will discuss next time, this causes water to move in also, creating root pressure. However, root pressure can only force water up for a few meters. It is certainly not sufficient to get water to the top of the giant Sequoia.

b. Transpiration (lab)
Water moves up the stem and into the leaf through the xylem vessels

36.8

Xylem vessels [!]leaf veins [!]water film covering leaf mesophyll [!]internal air spaces [!]stomata

Water is needed in the leaf to hydrate the leaf mseophyll cells, to provide a wet surface for gas exchangeand for photosynthesis, but most is lost through the stomata. The movement of water through the stomata is known as transpiration. A large tree can lose hundreds of gallons of water a day through the leaves. Transpiration is essentially the "cost" of gas exchange, but it has been harnessed to provide services - the evaporation of water cools the leaf and the continuous movement of water out of the veins pulls water up through the xylem from the roots.

Discussion Question:
Grasses like the ones in your lawn are monocots. Their apical meristems are located near the ground rather than at the end of branches. How is this relevant to lawn care, i.e. mowing?
(Campbell, 4th, pp.679-689, 697-701)


		c. Casparian strip The Casparian strip is made up of waxy material that is laid down in continuous belts around the endodermal cells surrounding the stele, the vascular tissue of the root. The Casparian strip forms a barrier that blocks water from moving through the cell walls (apoplast).In order for water and dissolved minerals to pass into the stele, they must move through the plasma membrane of the endodermis into the cytoplasmand pass into the vascular cells through plasmadesmata. The plasma membrane provides a selective barrier that helps to keep unwanted material out of the plant. In addition, because the stele is sealed off, water and minerals can't leak back out into the root cortex. 3. Upward mobility a. Root pressure Roots pump minerals into the stele. As we will discuss next time, this causes water to move in also, creating root pressure. However, root pressure can only force water up for a few meters. It is certainly not sufficient to get water to the top of the giant Sequoia.
		b. Transpiration (lab) Water moves up the stem and into the leaf through the xylem vessels		36.8
		Xylem vessels [!]leaf veins [!]water film covering leaf mesophyll [!]internal air spaces [!]stomata Water is needed in the leaf to hydrate the leaf mseophyll cells, to provide a wet surface for gas exchangeand for photosynthesis, but most is lost through the stomata. The movement of water through the stomata is known as transpiration. A large tree can lose hundreds of gallons of water a day through the leaves. Transpiration is essentially the "cost" of gas exchange, but it has been harnessed to provide services - the evaporation of water cools the leaf and the continuous movement of water out of the veins pulls water up through the xylem from the roots. Discussion Question: Grasses like the ones in your lawn are monocots. Their apical meristems are located near the ground rather than at the end of branches. How is this relevant to lawn care, i.e. mowing? (Campbell, 4th, pp.679-689, 697-701)