What makes plants different?

While you know that plants are very different from animals, you probably haven't really paid attention to the ways in which plants are as different from us as we would be from Martian aliens.  Read the material below and watch the video. Then answer the questions.  

Plant Cells 

Plant Cell Walls.

The cell wall is to the outside of the cell membrane and is made of cellulose- this has the texture of cardboard.  This means that plant cells are  never going to be bendable and flexible like a muscle cell. They will always be slightly rigid. This gives them structure and support without having a skeleton, but keeps them from being mobile.  

Cell walls can be made even more rigid and tough by adding a molecule called lignin- this is what gives cells a woody texture. In fact, wood is made up of cells that all have lignin in their cell walls. Woody cells die off when they are mature, leaving just a hollow cell wall. 

Photosynthesis

Plants have chloroplast and absorb CO2 from the atmosphere,  H2O from the soil and the energy from sunlight in order to make their own organic molecules(from that CO2 and H2O). Just like us, they need nitrogen, phosphorus, minerals etc and they absorb these from the soil

Plant Growth 

Growth of an organism happens for two different reasons

• • • adding new cells
    • elongating/enlarging existing cells

Plants do both of these, but unlike animals they continue to grow through out their life. This is called indeterminate  growth since it has no determined end or size.  

In this time  lapse video of a seedling, make sure you notice the following

• • • Which grows first, the root or the shoot?
    • When the roots grow, are they growing from the tips or from the base of the root?
    • When the shoot first starts to grow, how does it emerge from the soil without damaging the new leaves?
    •  Where does the young seedling get its nutrients to grow, before it has any true leaves to do photosynthesis? 
    • What happens to the cotyledons (the first embryonic leaves)?
    • When the shoot starts to mature, where do the new leaves come from- the shoot tip or the base?

Meristems

These are a unique plant tissue. The function of meristems is to do cell division and add new cells to the plants body through mitosis. Meristems can be found in different parts of the plants body, and will continue to divide for the whole life of the plant. 

Remember that we are focusing on the Biological Hierarchy for this section of the course. The reason that meristem tissues can keep going through mitosis and add new cells to a plants body, is because the meristematic cells are able to keep going through the cell cycle from G1--> Sphase --G2--mitosis--> ad infinitum.  The tissue functions because of the cells that make up that tissue. 

Here is a diagram showing you the locations of meristems at the shoot and root tips.  Since the are at the apex of the shoot and root , they are called the apical meristems

There are other locations, but those are for a botany course!