LIFE 103 1st Edition Lecture 18 Outline of Last Lecture I Plant Hormones II Auxins I III Auxins II IV Cytokinins V Gibberellins VI Abscisic acid Outline of Current Lecture I Exam topics II Ethylene III Light IV Phytochromes V Seasons Current Lecture Signal transduction and hormones II Exam topics VI VII VIII IX X XI XII XIII Chapter 37 soils and plant nutrition not on exam 400 ppm is concentration of CO2 in atmosphere today will go up Pg 815 skip pg 818 819 Fig 38 5 is important Pg 822 828 skip 829 and rest of chapter Chapter 39 whole chapter Exam next Wednesday Review session on Monday These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Clicker question this process amplifies the signal that results when a hormone binds with a receptor Transduction Clicker question how do proteins coded by homeotic genes affect plants They bind to DNA and affect gene expression and development Clicker question the structure protects the young shoot in monocot seedlings coleoptile I Dicot has an epicotyl to protect it Ethylene II III IV V Produced in response to mechanical stress induces triple response that helps growing plants avoid obstacles I Slowing of stem elongation II Thickening of the stem III Stem curvature Ethylene pulse associated with programmed cell death Ethylene triggers fruit ripening process which causes production of more ethylene I Why it s good to put fruits in bag because the gas collects and allows fruit to ripen faster Diagram of bananas treated with ethylene shows how they differ in ripeness Biology major a botany concentration I II III Learn I Biochemistry molecular biology genetics anatomy physiology evolution ecology II Chemistry physics soils geology Apply I Food and nutrition II Biofuels wood horticulture III Ecology and global change Interested I Professor Steingraeber David Steingraeber colostate edu Signal transduction II light and other responses What does light tell a plant I II Natural selection has favored plants that make the smartest decisions about growth and reproduction The best action for a plant to take may depend on the environment III IV V Seeds with small energy reserves might delay germination until light conditions are just right Trees at bottom of forest canopy should grow taller I Those at the top should grow wider to shade out competitors below Light can provide information about I If there is enough light for growth II Time of day time of year Light color and phytochromes I II III Leaves absorb red and blue light I They reflect green light and transmit far red light i Far red fast moving wavelengths of light as they get longer and slower you get to yellow orange and red This is the infrared spectrum humans can t see because too low of energy II Far red is the longest wavelength of light humans can see Phytochromes are proteins that absorb either red light or far red light They flip flop r red fr far red I When the Pr form they absorb red light and flip to the Pfr form II When in the Pfr they absorb far red light and flop to the Pr form Fig 39 19 I If you leave it sitting around there is a slow conversion II Over time the concentration of PFr form slowly declines III In natural sunlight there is more red light than far red light IV Down in the canopy the leaves at the bottom are exposed to far red light so they have Pr light Clicker question a tree has most of its Phytochromes in the Pfr form What might this mean The leaves are at the top of the canopy and are exposed to full sunlight I II Fig 39 17 shown with lettuce seeds The last color of light triggers the end of dormancy How do plants know what season it is I Days are longer in summer shorter in winter a Short day plants blossom in late summer fall or winter