|Stephen G. Saupe - Biology Department, College of St. Benedict/St. John's University, Collegeville, MN 56321; (320) 363-2782; firstname.lastname@example.org|
Gink and Go at the Playground
Scene: Gink is in the backyard with a ladder and some rope. Go comes out of the house and sees Gink busily trying to climb a tree.
|Go:||Hi Gink. What are you doing?|
|Gink:||Today I'm going to be a real swinger|
|Go:||Huh? What are you talking about?|
|Gink:||What does it look like? I'm going to put a swing in this tree.|
|Go:||I see. How are you going to do it?|
|Gink:||Well, I'm going to climb up in the tree with this ladder, tie the rope around that large branch and then I'm ready to swing like Tarzan (beat your chest and give a Tarzan yell)|
|Go:||Sounds like fun, can I help?|
|Gink:||Sure, I could use a little help because I have a problem.|
|Gink:||I don't know how to keep the swing the same height from the ground.|
|Go:||What do you mean?|
|Gink:||Well, I've been watching this tree and it has been growing about two feet every year. I'm afraid that next year my swing will be too high off the ground for me to reach it without my ladder.|
|Go:||Hey – no worries.|
|Gink:||Are you sure?|
|Go:||Positive. Don't you remember what Saupe told us about how plants grow?|
|Gink:||Of course not – I never listen to him.|
|Go:||Plants grow in length from the tips. This type of growth is called primary growth and it arises from the primary meristems.|
|Gink:||What's a happy stem?|
|Go:||Not happy stem, meristems!|
|Gink:||Just kidding – lighten up. I remember now that meristems are the only regions of the plant that are capable of cell division.|
|Go:||That’s right! Unlike animals, not all regions of the plant are capable of division. Cells only divide in the meristematic regions like those at the tips of roots and shoots.|
|Gink:||Oh, right...since the branch that I attached my swing to has already formed, it won't grown any higher. Just the tip of the plant will grow away from the branch. So how do plants get fatter?|
|Go:||Growth in girth is caused by other meristems, called secondary meristems. Secondary meristems develop after primary meristems. The vascular cambium is a secondary meristem that divides to produce xylem and phloem cells. In trees like this one, it is the innermost layer of the bark. Lateral roots, you know, come from another secondary meristem called the pericycle. It's found in the stele of the root.|
|Gink:||Sure…and I remember another secondary meristem - the cork cambium that produces cork.|
|Go:||Right! Saupe would be proud of you!|
|Gink:||Who cares what that geek thinks. Let's get to work!|
Compare and contrast primary and secondary meristems.
Name four meristems in plants and identify their function.
Explain why a swing doesn't move higher off the ground as a tree grows in height.
Offer an explanation why most plants can grow throughout their lifetime but animals cannot.
If apical meristems are responsible for growth in length, why does a lawn continue to grow after mowing?
Consider the different types of projections from a plant: stem branches, root branches, root hairs. From what is each derived?
Consider a root tip that is marked with ink dots at 1 mm intervals. As the root grows in length (primary growth), which of the following statements is true? (a) all of the marks will get further apart; (b) only the marks that are distant from the root tip will get further apart; (c) only the marks that are close to the root tip will become further separated; (d) there will be no change in the position of any of the marks. Explain.
Last updated: January 19, 2007 � Copyright by SG Saupe