Problem Set #12

Question 1

A meristem’s transition from vegetative to floral is control by what 3 factors

Answer 1

day length
prolonged cold exposure
plant age

Question 2

What is the difference between short-day, long-day and day-neutral plants?

Answer 2

Short-day plants flower in days with short light treatments!
Long-day plant flower in days with long light treatments!
Day-neutral plants are not affected by photoperiod!
Some plants also require a combination:!
(eg. short then long day, long then short day…)!

Question 3

A plant is maintained in a photoperiod that supports vegetative growth, but one of its leaves is subjected to a photoperiod that would normally induce flowering in this species of plant. Is this exposure of a single leaf sufficient to cause the plant transition to flowering or will it remain vegetative?

Answer 3

Once induction is perceived the leaf is permanently activated, single leaf will cause plant to flower

Question 4

What receptors are responsible for sensing light in photoperiod induced flowering?

Answer 4

phytochrome A and B

Question 5

What was the first plant to have its genome completely sequenced? When was the sequencing completed how many genes? why was this organism chosen?

Answer 5

2001 and 30,000…..fast life cycle

Question 6

After pollen lands on the stigma, it germinates to form a_______ that grows through the style guided by chemical signals generated by an ovule. Two________nuclei and one______ nucleus travel through this structure as it grows by tip extension. Plugs made of________are regularly deposited in the structure as the pollen intracellular contents stream toward the ovule

Answer 6

Pollen tube
sperm
vegetative
callose

Question 7

Self incompatibility describes what phenomenon?

Answer 7

The ability of a plant to reject its own pollen and, in some cases, the pollen of close relatives

Question 8

If a pollen grain with compatibility factor S 2 lands on a stigma of compatibility factor S1 S 2 what will happen?

Answer 8

Sequesters toxins and Pollen tube will develop?

Question 9

If a pollen grain with compatibility factor S 4 lands on the same stigma what will happen?

Answer 9

Releases toxins and inhibits growth?

Question 10

Two sperm nuclei are transmitted from the pollen to the ovule during fertilization. One fertilizes the egg producing a zygote that will become the plant embryo. What happens to the other sperm nucleus?

Answer 10

Double fertilization, resulting in a triploid endosperm used as a nutrient-rich source for the developing embryo

Question 11

The major storage organ in cereal crop seeds is the __ ,while in legumes the major storage organs are the__ .

Answer 11

endosperm

cotyledon

Question 12

Phosphate is stored in many seed types in what chemical form?

Answer 12

Phytate or phytic acid

Question 13

Mature seeds are dormant because they have significant abscisic acid content. As seeds break dormancy and absorb water what two signals play a critical early role in decreasing the effectiveness of abscisic acid in maintaining dormancy, while simultaneously activating nutrient mobilization from seed storage tissues?

Answer 13

light and hormones

Question 14

Define programmed cell death. How is it different from cell death associated with physical injury?

Answer 14

PCD is the deliberate termination of cell function and dismantling of the cell in an organism by that organism.
PCD is used for things like plant development and senescence. Whereas cell death from injury occurs but a hormone response is induced (i.e. Auxins)

Question 15

Give four specific examples of programmed cell death used in plant development.

Answer 15

root cap
trichome development
megaspore formation
leaf senescence

Question 16

Cavities and oil glands (such as those found in citrus peal) can form in living plant tissue through the combination of what two processes?

Answer 16

Lysigeny is dissolution of protoplast and cell wall!

Schizogeny is separation of cell walls to create an intercellular space

Question 17

What is senescence and how is it different from other forms of programmed cell death?

Answer 17

Senescence - deliberate termination of leaf, flower, and fruit
-Seasonal

Question 18

What hormone activates senescence? What hormone can reverse senescence in a leaf even after complete loss of chlorophyll?

Answer 18

Ethylene activates while

Cytokinins can rescue senescing leaves

Question 19

What is the hypersensitive response? How does it work to protect the plant from infection?

Answer 19

Hypersensitive response is a mechanism, used by plants, to prevent the spread of infection by microbial pathogens. The HR is characterized by the rapid death of cells in the local region surrounding an infection.

Question 20

What hormone is produced by some pathogens in an attempt to block the hypersensitive
response?

Answer 20

Cytokinins

Question 21

What is the difference between primary and secondary metabolism?

Answer 21

Primary metabolism is the complete collection of chemicals and reactions in an organism that support the organisms growth, development and reproduction!
Secondary metabolites are compounds that are not required for normal growth, development or reproduction of the organism that makes them. Important for mediating interactions with other organisms.

Question 22

Name three types of specialized plant structures in which secondary metabolites are
stored.

Answer 22

Glandular trichomes!
Secretory cavity in lemon leaf!
Resin duct in pine !

Question 23

What is the basic chemical unit of all isoprenoid secondary metabolites?

Answer 23

Isoprenoids are composed of 5-carbon isoprene units

Question 24

Trees give off a significant fraction of their total fixed carbon on hot days as what gas?

Answer 24

5% of fixed carbon is off gassed as isoprene, and contributes to haze!
May help stabilize photosynthetic membranes !

Question 25

When the diphosphate is removed from isopentenyl pyrophosphate it leaves a high-energy carbon centered cation (a carbocation) that can be used to extend a growing isoprene chain or form new carbon-carbon bonds making rings. Due to the high energy these reactions they can be hard to control and often result in several different products. What is the advantage to a plant in using such a system for secondary metabolite production?

Answer 25

Drive formation of many new carbon bonds and ring systems??

Question 26

What enzyme does the family of cholesterol lower drugs called ‘statins’ inhibit?

Answer 26

reductase

Question 27

List some general characteristics of alkaloids, isoprenoids and phenolics that might help you identify a secondary metabolite as belonging to one of these three classes of compound

Answer 27

Alkaloids: contain nitrogen
Isoprenoids:aromatic substances
Phenolics: generally not aromatic?

Question 28

Coniine is the major toxin produced by poison hemlock. Coniine poisoning sometimes occurs when people confuse hemlock with what edible relatives?

Answer 28

Carrots, fennel, parsley and parsnip, and can be confused with the flower Queen Anne’s Lace