Plant Physiology

Plant Physiology (Biology 327) - Dr. Stephen G. Saupe; College of St. Benedict/ St. John's University; Biology Department; Collegeville, MN 56321; (320) 363 - 2782; (320) 363 - 3202, fax; ssaupe@csbsju.edu

Phytochrome Effects?

1. Examine the data provided in Table 1. Based on these data:

is germination a phytochrome response? (cite evidence to support your answer)
if the phenomenon is caused by phytochrome, is this a VLFR, LFR or HIR response? Explain.
after a five minute exposure, in which of the following treatments would you expect the lettuce seeds to germinate: white light? green light? blue light? far red? Explain.

Table 1: Germination of Grand Rapids Lettuce Seeds after exposure to red or far-red light
Treatment	% Germination
none	8.5
red light	98
red followed by far-red light treatment	54
r, fr, r	100
r, fr, r, fr	43
r, fr, r, fr, r	99
r, fr, r, fr, r, fr	54
r, fr, r, fr, r, fr, r	98

2. Examine the data in Table 2.

is this an example of a phytochrome effect? Explain.
explain the interrelation of kinetin and light.

Table 2: Effect of kinetin and light on growth of bean leaf disks during a 48 hour period. Data from C.O. Miller. Plant Physiol. 31: 318 (1956)
[Kinetin] (μM)	Light	Increase in diameter (mm)
0	none	1.05
0.5	none	2.48
0	5 min red	2.58
0	5 min fr-red	1.01
0	5 min red, then 5 min far-red	1.17
0.5	5 min far red	2.49

3. Examine the data in Table 3.

describe the effect of red, far-red, and blue light treatments on anthocyanin synthesis
is this a phytochrome effect? Explain.
If this effect is mediated by phytochrome, is it an example of a VLFR, LFR or HIR response? Explain.

Table 3: Anthocyanin production in milo (Sorghum vulgare) seedlings. Seedlings were kept in the dark then treated as indicated. Treatments began when the seedlings were five days old. Data from Hopkins (1995)
Treatment	[Anthocyanin] (A₅₁₀)
27 hours red	0.0
27 hours far-red	0.0
3 hours blue + 24 hours dark	0.19
3 hours blue + 5 min R + 24 hours dark	0.19
3 hours blue + 5 min FR + 24 hours dark	0.05
3 hours blue + 5 min FR + 5 min R + 24 hours dark	0.19

4. The data in Table 4 provide an indication of how hormones may mediate the phytochrome response. Examine the data in the table and then answer the following questions:

What is the effect of GA on lettuce seed germination?
What is the effect of kinetin on lettuce seed germination?
What is the effect of ABA on lettuce seed germination?
Describe the interaction of GA, kinetin and ABA in lettuce seed germination.
Develop a model for light sensitive seed germination that includes phytochrome and hormone.

Table 4: Effect of hormones on lettuce seed germination in the dark
[GA] mM	% Germination
[GA] mM	Control (no addition)	+ kinetin	+ ABA	+ ABA + kinetin
0	10	15	0	0
0.05	21	27	0	17
0.5	66	69	0	57
5	95	97	0	73