Red White and Blue Tortilla Red White and Blue Tortilla ChipsChips

The Domestication of The Domestication of MaizeMaize

Physiology of PlantsPhysiology of Plants

Randy WayneRandy Wayne

Shoals Marine LabShoals Marine Lab

July, 2009July, 2009

Life: The Ability to Respond Life: The Ability to Respond Appropriately to the EnvironmentAppropriately to the Environment

ConsciousnessConsciousness, as , as defined as an defined as an awareness of the awareness of the external environmentexternal environment—the first step in —the first step in responding responding appropriately to the appropriately to the environmentenvironment, is a , is a characteristic of life characteristic of life and may have begun and may have begun with the first cell.with the first cell.

Plants Sense and Respond Plants Sense and Respond to the Environment to the Environment

If we were to walk If we were to walk quietly and quietly and observantly through observantly through a garden at the a garden at the Cornell Cornell PlantationsPlantations, it , it would become would become increasingly clear increasingly clear that it is a normal that it is a normal and ubiquitous and ubiquitous property of plants to property of plants to sensesense and and respondrespond to their environment. to their environment. http://www.plantations.cornell.edu/

Plants Sense and Respond Plants Sense and Respond to the Environment: to the Environment:

PhototropismPhototropismPlants sense the Plants sense the direction ofdirection of lightlight and bend or turn toward the light.and bend or turn toward the light.

Plants Sense and Respond Plants Sense and Respond to the Environment: to the Environment:

GravitropismGravitropism

Plants sense the Plants sense the vector ofvector of gravitygravity and the shoots and the shoots bend up; away bend up; away from the source from the source of the of the gravitational gravitational force, and the force, and the roots bend down; roots bend down; toward the toward the source of the source of the gravitational gravitational force.force.

Plants Sense and Respond Plants Sense and Respond to the Environment: to the Environment:

ThigmotropismThigmotropism

Plants, particularly vines, have a sense of Plants, particularly vines, have a sense of touchtouch. . When the When the tendrils tendrils come in contact with a support, come in contact with a support, they quickly respond to the they quickly respond to the mechanical forcemechanical force and and curl around the support. curl around the support. ThigmoThigmo is the Greek word is the Greek word for touch.for touch.

Venus’ Fly Traps Can Sense Venus’ Fly Traps Can Sense Touch, Capture Their Prey, Touch, Capture Their Prey, Secrete Digestive Enzymes Secrete Digestive Enzymes

and Absorb the Nitrogenous and Absorb the Nitrogenous NutrientsNutrients

MimosaMimosa Can Sense Touch Can Sense Touch and Heatand Heat

Plants Sense and Respond Plants Sense and Respond to the Environment: to the Environment:

PhotoperiodismPhotoperiodismPlants sense Plants sense day day lengthlength (or really (or really the the length of the length of the nightnight) so that ) so that they can flower in they can flower in the spring or fall, the spring or fall, when the days are when the days are short, or in the short, or in the summer, when the summer, when the days are long.days are long.

Circadian Circadian (about a (about a

day) day) RhythmsRhythmsPlants sense Plants sense the the duration duration of timeof time and and move their move their leaves leaves throughout a throughout a 24 h cycle.24 h cycle.

http://plantsinmotion.bio.indiana.edu/redirect.html

The Living World is But The Living World is But Mankind in the MakingMankind in the Making

Raoul Francé (1905) Raoul Francé (1905) wrote, wrote, “What grander “What grander lesson could the lesson could the speechless plants speechless plants give than that which give than that which they have taught us: they have taught us: thatthat theirtheir sensesense lifelife isis aa primitiveprimitive formform, , thethe beginningbeginning ofof thethe humanhuman mindmind... it tells ... it tells us that after all the us that after all the living world is but living world is but mankind in the mankind in the making, and that we making, and that we are but a part of all.”are but a part of all.”

Germination of Lettuce Germination of Lettuce SeedsSeeds

Seeds have a variety of requirements that ensure that Seeds have a variety of requirements that ensure that they germinate in the right place and the right time.they germinate in the right place and the right time.

Lettuce seeds need a pulse of red light (660 nm) to Lettuce seeds need a pulse of red light (660 nm) to germinate. germinate.

If the red light is immediately followed by a pulse of If the red light is immediately followed by a pulse of far-red light (730 nm), the seeds no longer germinate.far-red light (730 nm), the seeds no longer germinate.

The The photoreceptorphotoreceptor the senses the quality of the light the senses the quality of the light is called is called phytochromephytochrome (plant color). (plant color).

Germination of Lettuce Germination of Lettuce SeedsSeeds

The seeds can be exposed to many rounds of red The seeds can be exposed to many rounds of red and far-red pulses, but it is only the last pulse and far-red pulses, but it is only the last pulse that matters in inducing germination. that matters in inducing germination.

Harry Borthwick and Sterling Hendricks Harry Borthwick and Sterling Hendricks concluded that phytochrome acts like a switch. concluded that phytochrome acts like a switch. Light causes the interconversion between Light causes the interconversion between the red absorbing form (Pr) and the far-red the red absorbing form (Pr) and the far-red absorbing form (Pfr).absorbing form (Pfr). Only the far red Only the far red absorbing form causes germination.absorbing form causes germination.

PhytochromePhytochrome

Pr Pfr

Pr

Pfr

Phototropism: Discovery of the Phototropism: Discovery of the Site of PerceptionSite of Perception

Charles and Francis Darwin found that coleoptile bent Charles and Francis Darwin found that coleoptile bent toward toward blue lightblue light and the apex is required for the and the apex is required for the phototropic response even though the bending takes place phototropic response even though the bending takes place below the tip. below the tip.

They concluded that the They concluded that the tip tip of the coleoptile sensed the of the coleoptile sensed the light and then some “influence” light and then some “influence” traveled traveled from the tip to from the tip to the bending zone.the bending zone.

Phototropism: Discovery of Phototropism: Discovery of the Chemical Nature of the the Chemical Nature of the

StimulusStimulus

In order to test the possibility that a In order to test the possibility that a hormonehormone was produced was produced by the tip and transported down to the growing zone, Peter by the tip and transported down to the growing zone, Peter Boysen-Jensen inserted a piece of mica in order to block the Boysen-Jensen inserted a piece of mica in order to block the transport of the hormone and showed that transport of the transport of the hormone and showed that transport of the hormone toward the base occurs on the hormone toward the base occurs on the dark sidedark side of the plant of the plant as opposed to the side exposed to the unidirectional light.as opposed to the side exposed to the unidirectional light.

PhototropismPhototropism

Paal cut off coleoptile tips in the dark and Paal cut off coleoptile tips in the dark and exposed the tips to light. Then he replaced the exposed the tips to light. Then he replaced the tip on the plant but off centered to one side or tip on the plant but off centered to one side or the other. the other. He found that the coleoptile curved away from He found that the coleoptile curved away from the side that was exposed to the tip.the side that was exposed to the tip.

PhototropismPhototropism

Frits Went figured that if the influence was a Frits Went figured that if the influence was a hormone, he could trap it in a block of agar and then hormone, he could trap it in a block of agar and then put it asymmetrically on the coleoptile and induce put it asymmetrically on the coleoptile and induce curvature in the dark. It worked! Went named the curvature in the dark. It worked! Went named the hormone hormone auxinauxin, which means “to grow.”, which means “to grow.”

Humans Eat Plants, and Humans Eat Plants, and Human Urine Causes Human Urine Causes Coleoptiles to BendColeoptiles to Bend

Urine has traditionally been a convenient (and cheap) Urine has traditionally been a convenient (and cheap) source for the isolation of chemicals (e.g. guanine and source for the isolation of chemicals (e.g. guanine and other purines).other purines).

F. Kogl and A. J. Haagen-Smit first isolated auxin from F. Kogl and A. J. Haagen-Smit first isolated auxin from human urine in 1931.human urine in 1931.

Soon Auxin was Isolated From Soon Auxin was Isolated From Plants Too!Plants Too!

Winslow Briggs Showed that blue light Winslow Briggs Showed that blue light causes bending in coleoptiles by causes bending in coleoptiles by

causing a redistribution of auxin from causing a redistribution of auxin from the lighter side to the darker side.the lighter side to the darker side.

Added Auxin Causes Added Auxin Causes Coleoptiles to Elongate Coleoptiles to Elongate

The Mechanism of The Mechanism of PhototropismPhototropism

Blue lightBlue light induces induces bending by causing a bending by causing a lateral lateral redistributionredistribution of the of the hormone auxinhormone auxin from from the lighted side of the the lighted side of the tip to the dark side.tip to the dark side.

The The increased auxin increased auxin on the dark side on the dark side stimulates stimulates elongationelongation, which , which results in bending results in bending toward the light.toward the light.

How Auxin May Induce Long Term How Auxin May Induce Long Term GrowthGrowth

Ethylene and Aging Ethylene and Aging ResponsesResponses

In the 1880s, after the In the 1880s, after the installation of installation of coal gas coal gas lampslamps, people began to , people began to notice that notice that leaves dropped leaves dropped off the plantsoff the plants that were that were exposed to gas leaks.exposed to gas leaks.

In 1910, H. H. Cousins In 1910, H. H. Cousins noticed that rotten oranges noticed that rotten oranges caused the caused the premature premature ripening of bananasripening of bananas and and ethylene ethylene produced by the produced by the oranges was the cause of oranges was the cause of ripening.ripening.

In 1934, R. Gane classified In 1934, R. Gane classified ethylene (Cethylene (C22HH44) as a ) as a hormonehormone..

Ethylene Promotes Senescence (Aging) of Many Flowers

• Older flowers produce ethylene.• The ethylene promotes the

senescence of flowers, which has evolved to rid the plant of older flowers that have most likely been pollinated so that the young not-yet-pollinated flowers have a better chance of being pollinated.

• This is good for the plant, but not for people who like flowers in their home.

Ethylene Promotes Ripening (Aging) of Many Fruits

Ripening, which has evolved to promote fruit dispersal, involves the synthesis of sugars, the degradation of cell walls to make the fruits softer and the production of chemicals that provide color, flavors and aromas.

Ethylene Antagonists Ethylene Antagonists Prevent Aging Prevent Aging

1-MCP (1 methyl 1-MCP (1 methyl cyclopropene; Ccyclopropene; C44HH66), ), an ethylene (Can ethylene (C22HH44) ) antagonist prevents antagonist prevents flower senescence flower senescence and further fruit and further fruit ripening.ripening.

1-MCP binds tightly 1-MCP binds tightly to the ethylene to the ethylene receptor thereby receptor thereby blocking the effects blocking the effects of ethylene. of ethylene.

AbscissionAbscission

Roles of Ethylene and Auxin during Roles of Ethylene and Auxin during AbscissionAbscission

Healthy leaves, Healthy leaves, flowers and fruits flowers and fruits produce produce auxinauxin, , which is which is transported down transported down toward the stem. toward the stem. The cells in the The cells in the region of the region of the petiole known as petiole known as the abscission the abscission zone are zone are insensitive to insensitive to ethyleneethylene..

In response to In response to age, touch or day age, touch or day length, the length, the amount of auxin amount of auxin produced by the produced by the organ decreases. organ decreases. When the level of When the level of auxin drops, cells auxin drops, cells in the abscission in the abscission zone become zone become sensitivesensitive to to ethylene.ethylene.

The increase in The increase in ethylene ethylene activates the activates the enzymes that enzymes that digest the cell digest the cell walls in the walls in the abscission zone, abscission zone, and the and the weakened organ weakened organ falls.falls.

Synthetic Auxins Cause Synthetic Auxins Cause DefoliationDefoliation

While Art Galston (1943) was While Art Galston (1943) was looking for a chemical means to looking for a chemical means to make soybeans flower and fruit make soybeans flower and fruit earlier so that they could thrive earlier so that they could thrive in regions with a short growing in regions with a short growing season, he discovered that a season, he discovered that a low low concentration of a synthetic concentration of a synthetic auxinauxin 2,4,5-triiodoacetic acid) 2,4,5-triiodoacetic acid) would speed up flowing. would speed up flowing.

He also noticed that higher He also noticed that higher concentrations were not good for concentrations were not good for speeding up flowering even more speeding up flowering even more because because higher concentrations higher concentrations caused the leaves to fall offcaused the leaves to fall off..

Cornell Alumnus, The “price was right.”

DefoliationDefoliation

The army was The army was interested in the interested in the ability of 2,4,5-T to ability of 2,4,5-T to defoliate jungle defoliate jungle plants in Viet Nam so plants in Viet Nam so that the Viet Cong that the Viet Cong would have nowhere would have nowhere to hide.to hide.

The army mixed The army mixed 2,4,5-T with two 2,4,5-T with two other synthetic other synthetic auxins to make Agent auxins to make Agent Orange. Orange.

Agent OrangeAgent Orange

The herbicide mixture was named The herbicide mixture was named Agent OrangeAgent Orange after the color of the stripes on the 55 gallon drums after the color of the stripes on the 55 gallon drums it came in. it came in.

Agent Orange contained Agent Orange contained dioxindioxin, a byproduct of 2,4,5-, a byproduct of 2,4,5-T manufacture, which was a well known T manufacture, which was a well known carcinogencarcinogen..

Dioxin Increases the Risk Dioxin Increases the Risk for:for:

D1. Birth Defects (Spina bifida andAnencephaly)

D2. Chloracne D3. Non-Hodgkin’s Lymphoma D4. Soft Tissue Sarcomas D5. Peripheral Neuropathy D6. Hodgkin’s Disease D7. Porphyria Cutanea Tarda D8. Multiple Myeloma D9. Respiratory Cancers D10. Prostate Cancer D11. Spina Bifida D12. Diabetes D13. Chronic Lymphocytic

Leukemia

Spina bifida and Spina bifida and Anencephaly Anencephaly

BioethicsBioethics

In 2003, Dr. Galston In 2003, Dr. Galston reconsidered the arc of his reconsidered the arc of his research.research.

““You know,” he said, “nothing You know,” he said, “nothing that you do in science is that you do in science is guaranteed to result in guaranteed to result in benefits for mankind. benefits for mankind. Any Any discovery, I believe, is discovery, I believe, is morally neutral and it can morally neutral and it can be turned either to be turned either to constructive ends or constructive ends or destructive endsdestructive ends.”.”

He concluded: “That’s not the He concluded: “That’s not the fault of science.” (Obituary in fault of science.” (Obituary in NYT June 23, 2008).NYT June 23, 2008).

Archibald V. HillArchibald V. Hill

““It is true that scientific It is true that scientific research has opened up the research has opened up the possibility of unprecedented possibility of unprecedented good, or unlimited harm, for good, or unlimited harm, for mankind; but the use that is mankind; but the use that is made of it depends in the end made of it depends in the end on the moral judgments of the on the moral judgments of the whole community of men. It is whole community of men. It is totally impossible now to totally impossible now to reverse the process of reverse the process of discovery: it will certainly go discovery: it will certainly go on. on. To help guide its use To help guide its use aright is not a scientific aright is not a scientific dilemma, but the dilemma, but the honourable and compelling honourable and compelling duty of a good citizen.”duty of a good citizen.”

Erwin ChargaffErwin Chargaff

• The goal of science has The goal of science has changed from exploration changed from exploration and explanation and explanation (knowledge) to exploitation (knowledge) to exploitation (intellectual property and (intellectual property and profit).profit).

• ““What I have called the What I have called the change in the moral climate change in the moral climate is 1) is 1) that the majority [of that the majority [of scientists] seem to agree scientists] seem to agree that what can be done that what can be done must be donemust be done…”…”

The Reaction of Scientific The Reaction of Scientific Progress Upon Human Life and Progress Upon Human Life and

ThoughtThought You are a shareholder You are a shareholder

in the world and have in the world and have its future in your hands.its future in your hands.

Although it is often Although it is often stated that demand stated that demand creates supply, it is creates supply, it is often the other way often the other way around, supply creates around, supply creates demand.demand.

When science produces When science produces something, people will something, people will buy it.buy it.

Aldous HuxleyAldous Huxley

What do You Value about being Human?

• How do you measure the value of being human?

• Are you willing to cede your input on this question to biotechnologists using a business model to do science?

• Are you willing to take the time to maintain and sharpen your knowledge of biology in order to make informed, knowledgeable and wise personal, athletic, business and political decisions that reflect your values about the value of being human? http://www.hgalert.org/

I Wish You Enough I Wish You Enough

I wish you I wish you enoughenough sun to keep your attitude sun to keep your attitude bright no matter how gray the day may bright no matter how gray the day may appear.appear.

I wish you I wish you enoughenough rain to appreciate the sun rain to appreciate the sun even more.even more.

I wish you I wish you enoughenough happiness to keep your happiness to keep your spirit alive and everlasting.spirit alive and everlasting.

I wish you I wish you enoughenough pain so that even the pain so that even the smallest of joys in life may appear bigger. smallest of joys in life may appear bigger.

I wish you I wish you enoughenough gain to satisfy your gain to satisfy your wanting.wanting.

I wish you I wish you enoughenough loss to appreciate all that loss to appreciate all that you possess. you possess.

I wish you I wish you enoughenough hellos to get you through hellos to get you through the final good-bye.the final good-bye.

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