LIFE 103 1st Edition Lecture 19 Outline of Last Lecture I. Exam topics II. Ethylene III. LightIV. PhytochromesV. SeasonsOutline of Current Lecture I. SeasonsII. Other stimuli and responses III. Defenses against herbivoresIV. Pathogen defenses I. Hypersensitive responseII.Current LectureHow do plants know what season it is? V. Days are longer in summer, shorter in winter I. Short-day plants blossom in late summer, fall or winter II. Long-day plants blossom in late spring or early summer VI. Plants actually cue on night length! I. Short day = long night, long day = short night II. Bursts of light at night can signal a short night VII. Phytochromes signal short night if they are exposed to RED light VIII. Graph with time on x-axis, Pfr on y-axis, and over time, the slope decreases 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.IX. There is a threshold of Pfr concentration that is a 0 slope line at the bottom and determines when to flower or not X. Fig. 39.21 XI. Fig. 39.22 Can one part of the plant signal the whole plant to flower? I. Fig. 39.23 II. Yes! III. Phytochromes are in the leaves but they signal other hormones that induce flowering Clicker question: “long day” plants can be induced to flower if they are exposed to: a short night Other stimuli and responses I. Read section 39.4 to learn more about plant responses to I. Gravity II. Mechanical stimuliIII. Environmental stresses i. Droughtii. Nutrient stressesiii. Water stresses Plant defenses against herbivoresI. Many plants have chemical defenses that are harmful to herbivoresII. The jackbean produces an unusual amino acid canavanine that is very simple to argenineI. When an herbivore builds proteins with canavanine, they don’t work, killing the herbivore (taste bad to the herbivore) III. Soy beans contain a protein that disables the digestive enzyme trypsin I. When mammalian herbivores eat it, they cannot digest the proteins contained in the soy IV. Fig. 39.28 Pathogen defensesI. Gene-for-gene recognition: I. Plants recognize identity of pathogen-derived moleculesi. Recognition is by the protein of an R (resistance) gene. There are 100s of R genesII. Recognition leads to responsesII. Hypersensitive response: death of infected cells and antibiotic production at infected site III. Systemic acquired resistance: non-specific defense genes turned on throughout plant fordays after recognition IV. Fig.
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