Lesson 2 - Transport in Plants

Nonvascular Plants

Cannot grow high above the ground, because they do not have the necessary tissues for it.

Examples: Moss, Liverwort, Hornwort, and Green Algae.

Vascular Plants

Can grow high and tall because they have the tissues necessary for it, namely: phloem and xylem.

Examples: Ferns, Gymnosperms, and Flower Plants.

Xylem

Makes the transport of water and minerals possible.

From the roots, they will carry the water and minerals to all parts of the body.

It occupies the central part of the plants, which is the largest.

Phloem

Phloem is responsible for transporting the products of photosynthesis throughout the plant body.

From the leaves of the plant, they will deliver the product substance to the rest of the body.

It occupies the marginal side of the plants.

Radial Rays

In the trees, we can find _________ along their trunks.

These tissues are common in woody plants for radial distribution of food.

Apoplast Pathway

This includes movement through the cell walls and spaces between cells (cell wall to cell wall).

Symplast Pathway

Here, water and minerals pass through a continuum of cytoplasm between cells, called plasmodesma (cytoplasm to cytoplasm).

Transmembrane Pathway

This involves transport between cells across the membranes of vacuoles within cells (cytoplasm to cell wall).

Transpiration

The release of water vapor through openings in the leaves, causing a pressure that pulls the water up in the plants.

Partly, this happens because of the cohesive forces between water molecules and adhesive forces between water molecules and the walls of the xylem vessels.

In addition to this, osmosis and diffusion are also passive forces that help molecules to move from one cell to another.

Water Potential

The one of the main factors that regulate the transport process in plants. This represents free energy or the potential to do work.

Furthermore, this is used to predict where water will move.

Take note that water will move from a cell or solution with higher water potential to a cell or solution with lower water potential.

Guttation

This happens if sunlight is absent.

During nighttime, the rate of transpiration is low, that’s why ions accumulate in the roots of plants, causing root pressure buildup.

This will cause the water to enter the cells by osmosis.

Turgor Pressure

The influx of water into the cell can produce this kind of pressure.

This causes the plasma membrane to push against the cell wall, during the transport in phloem.

Pressure Flow Theory

This can demonstrate turgor pressure; it states that dissolved carbohydrates which flow from a source, are brought to a sink where these either stored or utilized.

Sucrose travels from mesophyll cells of the leaves to the companion and sieve cells through symplast.

However, majority of the sucrose molecules are moved to the sieve cells through the apoplast pathway.

Bulk Flow

This takes place in the sieve tubes.

It occurs because of difference in water potential between sieve tubes and the nearby xylem cells.

The increased turgor pressure in the sieve tubes drives the fluid throughout the plant systems.