New User Special Price Expires in

Let's log you in.

Sign in with Facebook


Don't have a StudySoup account? Create one here!


Create a StudySoup account

Be part of our community, it's free to join!

Sign up with Facebook


Create your account
By creating an account you agree to StudySoup's terms and conditions and privacy policy

Already have a StudySoup account? Login here

Biology 4.14.16

by: Shayla Pedigo

Biology 4.14.16 Bio 111 - Fundamentals of Biology II

Shayla Pedigo

Preview These Notes for FREE

Get a free preview of these Notes, just enter your email below.

Unlock Preview
Unlock Preview

Preview these materials now for free

Why put in your email? Get access to more of this material and other relevant free materials for your school

View Preview

About this Document

These are good for if you missed lecture or need a recap.
Athena Anderson
Class Notes
Biology, Biology 11100
25 ?




Popular in Biology

Popular in Biology

This 7 page Class Notes was uploaded by Shayla Pedigo on Sunday April 17, 2016. The Class Notes belongs to Bio 111 - Fundamentals of Biology II at Purdue University taught by Athena Anderson in Spring 2016. Since its upload, it has received 7 views. For similar materials see Biology in Biology at Purdue University.

Similar to Bio 111 - Fundamentals of Biology II at Purdue


Reviews for Biology 4.14.16


Report this Material


What is Karma?


Karma is the currency of StudySoup.

You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!

Date Created: 04/17/16
Biology 4.14.16 Ethylene Produced in response to stresses • drought • flood • mechanical pressure • injury • infection And as part of normal life cycle • fruit ripening • programmed cell death Ethylene & Mechanical Stress The “Triple Response”- example scenario, pea seedling growing through soil encounters a rock; the stress on its shoot tip causes ethylene production 1. stem elongation slows (stops the stress) 2. stem thickens (increases strength) 3. stem grows horizontally (increases chance of getting past obstacle) The “Triple Response”- example scenario, pea seedling growing through soil encounters a rock; the stress on its shoot tip causes ethylene production • ethylene produced in a burst, the effects of which fade with time • when effects wear off, shoot attempts vertical growth again • if barrier still present, triple response repeated • this continues until shoot is free of barrier, or plant dies of nutrient/ water deficiency Ethylene & Senescence Senescence: programmed death of certain cells, organs, or entire plant • leaves dropped (at once in deciduous trees, continuously in evergreens) • death of annual plants after flowering • shriveling of flower petals Apoptosis: process of cell death (remember development lecture), burst of ethylene usually required Ethylene & Leaf Abscission Leaf Abscission: detachment of leaf from stem following apoptosis during senescence • helps prevent desiccation during winter in deciduous trees • nutrients taken from leaves & stored in stems • nutrients recycled into new leaves in spring Where Do Fall Colors Come From? • Deciduous trees are programmed to lose their leaves all at once in autumn (senescence) • Cells in leaves die (apoptosis), and nutrients are removed to stems. Chlorophylls are disassembled first, allowing other pigments (red, yellow, orange) to be seen. • Nutrients taken from leaves and stored in stems, then leaves are dropped (abscission) Ethylene & Fruit Ripening Immature fleshy fruits are tart, hard, & green, which help to protect developing seeds from herbivores For many species, burst of ethylene triggers fruit maturation Once ripe, mature fruits attract animals which eat them & disperse the seeds in their droppings  made soft by enzymatic breakdown of cell walls  made sweet by conversion of starches into sugars  enticing smells & bright colors advertise ripeness Photomorphogenesis Key events in plant growth & development that are triggered by light:  Etiolation: morphological adaptations for growing in darkness  De-etiolation (greening): when stem reaches light, shoot growth slows, leaves expand, roots elongate, chlorophyll produced Blue-Light Photoreceptors Light in the blue wavelengths initiates: • Growth toward light source • Light-induced stomatal opening • Light-induced slowing of hypocotyl elongation Phytochromes Detect red light wavelengths  Red light (~600nm) instigates germination  Far-red light (~730nm, dark) inhibits germination Experiments alternating flashes of red & far-red light on seeds showed that they respond to the last flash (reversible response) Phytochromes & Shade Avoidance Phytochromes also provide info about light intensity  they can detect the difference in ratio of red to far-red light resulting from shading of other plants Phytochromes also provide info. about light intensity • when plant that needs bright sunlight is shaded, phytochromes trigger greater energy expenditure on growing tall Phytochromes also provide info. about light intensity • when tree is exposed to right intensity of sunlight, phytochromes inhibit vertical growth & stimulate branching Circadian Rhythms Even under experimentally-controlled conditions, many physiological processes in plants maintain an approximate 24-hour schedule  opening & closing stomata  production of photosynthetic enzymes  raising & lowering leaves  opening & closing flowers Photoperiodism Physiological response to photoperiod (relative lengths of night & day); on annual time scale Flowering schedule is important example • short-day plants bloom when day length is below a certain threshold; usually in late summer, fall, winter; chrysanthemums, poinsettias, some soybean varieties Physiological response to photoperiod (relative lengths of night & day); on annual time scale Flowering schedule is important example • long-day plants bloom when day length is above a certain threshold; usually in late spring, early summer; spinach, radishes, irises, cereals Physiological response to photoperiod (relative lengths of night & day); on annual time scale Flowering schedule is important example • day-neutral plants are unaffected by photoperiod & flower when they reach a certain stage of maturity, regardless of day length; tomatoes, rice, dandelions Flowering Hormone Leaves detect changes in photoperiod & produce signaling molecules that trigger flower bloom • only one leaf is required for photoperiod to be recognized & flowering triggered • signaling molecule is a protein, coded for by gene called Flowering Locus T (FT), which is activated when conditions are right for flowering • FT protein travels from leaf to shoot apical meristem & causes transition of bud from vegetative to flowering state Tropisms Any growth response that results in plants curving towards or away from stimuli • phototropism: light • gravitropism (geotropism): gravity • thigmotropism: touch or other mechanical perturbation (like wind) Phototropism Positive: plant organs grow toward light • most often seen in shoots • cells on “dark” side of plant elongate faster than on “light” side Negative: plant organs grow away from light • most often seen in roots • cells on “light” side elongate faster than those on “dark” side Gravitropism Useful for roots & shoots that start to grow underground, where light can’t reach • roots display positive gravitropism • shoots display negative gravitropism Response occurs as soon as seed germinates & organs grow in appropriate direction no matter how seed is oriented when it lands Statoliths: dense cytoplasmic components that settle to lower portions of cell in response to gravity One hypothesis for how this works: 1. aggregating statoliths trigger redistribution of calcium 2. redistribution of calcium causes lateral auxin transport in root 3. auxin accumulates on lower side of root (the ‘underside’) 4. at high concentration, auxin slows elongation of cells here, meaning that cells on opposite side elongate faster, causing root to curve downward Thigmotropism Comes in several forms • trees in windy habitats grow shorter & thicker than their sheltered conspecifics, making them better able to resist strong winds • plants that use objects for climbing have positively thigmotropic organs (like tendrils) • plants that close when touched, possibly to protect themselves from damage or herbivory, are negatively thigmotropic Environmental Stress Important factor determining geographic ranges of plant species • Abiotic stress: caused by non-living things like heat, light, water, etc • Biotic stresses: caused by living things like herbivores, pathogens • Drought: close stomata, close leaves, drop leaves, • Flood: produce ethylene that causes death of some cells, which then serve as ‘snorkels’ that provide air to submerged roots • Heat: heat-shock proteins produced during high temperatures, which protect other proteins from being denatured • Cold: increase unsaturated fatty acids in cell membranes


Buy Material

Are you sure you want to buy this material for

25 Karma

Buy Material

BOOM! Enjoy Your Free Notes!

We've added these Notes to your profile, click here to view them now.


You're already Subscribed!

Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'

Why people love StudySoup

Bentley McCaw University of Florida

"I was shooting for a perfect 4.0 GPA this semester. Having StudySoup as a study aid was critical to helping me achieve my goal...and I nailed it!"

Janice Dongeun University of Washington

"I used the money I made selling my notes & study guides to pay for spring break in Olympia, Washington...which was Sweet!"

Steve Martinelli UC Los Angeles

"There's no way I would have passed my Organic Chemistry class this semester without the notes and study guides I got from StudySoup."


"Their 'Elite Notetakers' are making over $1,200/month in sales by creating high quality content that helps their classmates in a time of need."

Become an Elite Notetaker and start selling your notes online!

Refund Policy


All subscriptions to StudySoup are paid in full at the time of subscribing. To change your credit card information or to cancel your subscription, go to "Edit Settings". All credit card information will be available there. If you should decide to cancel your subscription, it will continue to be valid until the next payment period, as all payments for the current period were made in advance. For special circumstances, please email


StudySoup has more than 1 million course-specific study resources to help students study smarter. If you’re having trouble finding what you’re looking for, our customer support team can help you find what you need! Feel free to contact them here:

Recurring Subscriptions: If you have canceled your recurring subscription on the day of renewal and have not downloaded any documents, you may request a refund by submitting an email to

Satisfaction Guarantee: If you’re not satisfied with your subscription, you can contact us for further help. Contact must be made within 3 business days of your subscription purchase and your refund request will be subject for review.

Please Note: Refunds can never be provided more than 30 days after the initial purchase date regardless of your activity on the site.