Warm Up 1/31

List the steps for germination of a starchy seed. (outline)
1. Imbibition - absorption of water due to low water potential in the dry seed, which rehydrates living cells in the seed and allows the cells to become metabolically active; embryo increases respiration
2. Formation of gibberellin - gibberellic acid is released
3. GA stimulates amylase, a digestive enzyme that breaks down starch, to be produced
4. Digestion of starch into maltose in the food stores of the seed
5. Maltose is transported from food stores to the growth regions of the seedlings, including the embryo root and the shoot tissue.
6. Maltose is converted to glucose, which is used in aerobic cell respiration as a source of energy, or is used to synthesize cellulose or other substances needed for growth.

2. Explain how flowering is controlled in long-day and short-day plants, including the role of phytochrome.

• Flowering is controlled by phytochrome, which is affected by light (photoperiodicity)
• Phytochrome exists in two forms:
  •  A red (P_r) form absorbs red light (~660 nm) and is converted into a far red form (P_fr)
  • A far red (P_fr) form absorbs far red light (~730 nm) and is converted into a red form (P_r)
• The P_fr form is the active form of phytochrome, while the P_r form is the inactive form of phytochrome
• Sunlight contains more red light, so the P_fr form is predominant during the day, with the gradual reversion to the P_r form occurring at night
• In long day plants, the active P_fr form is a promoter of flowering and so flowering is induced when the night period is less than a critical length and P_fr levels are high
• In short day plants, the active P_fr form is an inhibitor of flowering and so flowering is induced when the night period is greater than a critical length and P_fr levels are low

Warm Up 1/27 - Plant Science

1. Of what values are tubers, type of stem modification, to the survival of plant species?
Tubers allow plants to store more carbohydrates.

2. When moving a plant from one place to another, why is it important to leave original soil around the roots?
The original soil should be left around the roots to ensure that all root hairs are transferred to the new location.  The original soil also contains the necessary nutrients for the new plant.  With some of the old soil, plants will ensure that they have enough of the necessary nutrients and can slowly adjust to the nutrients found in the new soil.  A direct change to the new soil could cause the plant go into shock and die.

3. What is the usual cause when a plant wilts?
Plants wilt when the water content within their cells becomes too low.  This often happens when the solid around a plant gets too dry or too salty, as this prevents water from moving into the plant.

4. Explain when a seed would be a sink and when it would be a source.
A seed would be a sink when it uses or stores sugar.  A seed would be a source when it produces sugar.

5. Why is it necessary that veins are relatively close together in leaves?
Phloem is located in all of the veins of the leaf, so veins help transport minerals and nutrients.  The distance between veins shows how well the veins are supplying nutrients to the leaf.  The more veins there are, the closer together the veins will be, and the more nutrients the leaf will be supplied with.

Warm Up 1/14

1. What is the importance of standard deviation with regards to the mean?
Two sets of data can have the same mean but be totally different.  The standard deviation shows the range of the data and helps more accurately compare two sets of data with the same mean.

2. What do error bars indicate?
Error bars are a graphical representation of the variability of data that show the degree of uncertainty relative to each data marker in a series.  They show the spread of measurements around a central tendency on a graph.  Error bars usually show the range of data, standard deviation or the 95% confidence intervals.

3. What percentage of values fall within 1 standard deviation of the mean?  And 2?
68% of the values fall within one standard deviation of the mean.  95% fall within two standard deviations.