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# Meristematic Region (page 2)

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Source:
Author: Janice VanCleave

### Try New Approaches

1. Does the rate of meristematic growth in the bean plants change during different periods of the day? Repeat the experiment marking only the three sections of the stems above the cotyledons. Measure these sections at two-hour intervals during the day, starting early in the morning and stopping at sunset.
2. Does the apical meristem growth rate differ in different dicot plants? Repeat the original experiment using different kinds of bean seedlings such as pinto, lima, and red kidney beans. For a better comparison of the growth, divide the area above the cotyledon of each plant into four or more sections. Science Fair Hint: Use the bean seedlings as the control so that growth of the other seedlings is compared to the bean seedlings. Use diagrams showing the changes in the length of each section as part of a project display.

### Design Your Own Experiment

1. The interval in a 24-hour period in which an organism is exposed to light is called a photoperiod (length of daylight and darkness). The responses of organisms to changes in the photoperiod is called photoperiodism. Design an experiment to determine if light duration affects the rate of meristematic growth. One way is by repeating the original experiment using three test groups of plants with 3 cups of plants in each group. Make every effort to vary only the amount of light that each group receives. Loosely cover the cups in one group with clear cellophane, taping the edges and top of the cellophane together to form a transparent (allows light to pass through) tubelike "hat" over each cup. Use wax paper to prepare a translucent (allows some light to pass through, though this light is diffused—spread out in different directions) "hat" for the second group, and aluminum foil to prepare an opaque (doesn't allow light to pass through) "hat" for the third group. Let the cups with the opaque hats be the control group. Lift the hats and measure the plants daily.
2. Plants grow in different environments with different nutrients. Design an experiment to determine how nutrients affect meristematic growth. One way is to repeat the original experiment using three sets of plants with the independent variable being nutrient. You will need to determine a method of growing the plants in soils from three different regions. Take care in the design of the experiment to keep all factors constant except for the independent variable, soil, for each set of plants the same.

### Get the Facts

1. Some plants live for hundreds and even thousands of years. Some bristlecone pines found in eastern California have been documented as being many thousands of years old. Theoretically these plants can grow forever by substituting new cells for aging and nonfunctioning cells. This potential for continuous growth is called open growth and involves apical and secondary meristems. Growth from apical meristems is called primary growth while growth from lateral meristems found in the cambrium (growth layer in plant stems) is called secondary growth. How does primary and secondary growth affect the size of a plant? What produces growth rings in some plants? Do all plants have cambrium? For more information, see a biology text.
2. Some plants have a main stem that grows taller than other stems on the plant. This is called a terminal shoot. What causes a terminal shoot? What is apical dominance? For more information, see Janice VanCleave's A+ Projects in Biology (New York: Wiley, 1993), pp. 57–62.
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