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Figure Center of meristem

Figure Cell in root tip (or shoot) Amyloplasts are pulled to bottom of cells by gravity Activated pressure receptors Gravity

Figure Auxin distribution Gravity Auxin 1. Normal distribution of auxin. 2. Root tip rotated. 3. Auxin is redistributed, move to bottom. 4. Root bends.

Figure 40.3a (a) Shoots bend toward full-spectrum light.

Figure 40.3b (b) Shoots bend specifically toward blue light.

Figure 40.5 Light is not sensed at the tip of the coleoptile. Light is sensed at the tip of a coleoptile. Where is light sensed to initiate phototropism in grass seedlings? Light Light responsible for triggering phototropism is sensed at the coleoptile tip. Control: Bends toward light Tip removed: No bending Tip covered: No bending Lower portion of coleoptile covered: Bends toward light 1. Cells at coleoptile tip sense light. 2. Hormone travels from tip down the coleoptile. 3. Cells lower in coleoptile respond to hormone. Bending results. Light (stimulus) Sensing tissue Hormonal signal Responding tissue This interpretation explains the hormone concept, but does not explain differential growth on the lighted and shaded sides of the coleoptile… Based on what you know about gravitropism, give a parsimonious (i.e. parallel) interpretation.

Biology: life study of What is Life? Cellular Structure: the unit of life, one or many Growth: cell enlargement, cell number Evolution: long term adaptation Behavior: short term response to stimuli Reproduction: avoid extinction at death Metabolism: photosynthesis, respiration, fermentation, digestion, gas exchange, secretion, excretion, circulation--processing materials and energy Movement: intracellular, movement, locomotion Properties of Life

Obtaining Food Autotrophs use ambient energy and carbon dioxide to make their own organic molecules. So the only matter they need to take up is minerals! Sadly they are sometimes called “plant food.”

Johann Baptista van Helmont Physician Scientist In 1648 experiment with Salix (willow) he tested whether the bulk of a plant comes from the soil or from some other source. His experiment was carefully documented but, because he was so far ahead of his time, his conclusion was wrong. Interestingly, however, his results suggest that plants do use soil minerals for growth. In the light of knowledge of carbon dioxide gas, the project shows that the plant grows mostly from air.

200 lbs soil 169 lbs + 3 oz sapling 200 lbs - 2 oz soil Because the role of air was not understood yet, van Helmont concluded that the weight increase was due only to water…WRONG. sunlight H2OH2O 5 lbs branch Adapted from: Figure 39.1 Page 776 Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Even if the plant is 90% water, the 10% dry weight (16.9 lbs) would have to come from somewhere.

200 lbs soil 169 lbs + 3 oz sapling 200 lbs - 2 oz soil Because the role of air was not understood yet, van Helmont concluded that the weight increase was due only to water…WRONG. sunlight H2OH2O CO 2 5 lbs branch O2O2 CH 2 O Adapted from: Figure 39.1 Page 776 Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley This decrease could be sample error, or minerals taken from the soil by the growing plant. Even if the plant is 90% water, the 10% dry weight (16.9 lbs) would have to come from somewhere. Could it be minerals from the soil?

Autotrophic Organisms Typically autotrophs carry out photosynthesis: CO 2 + H 2 O O 2 + CH 2 O As you can see, the plant needs NO food. But the enzymes and ion transporters for photosynthesis require metal cofactors: The essential macroelements are: CHOPKNS CaFe Mg The essential microelements are: CuMn CoZn Si Mo B Al Cl lightlight chlorophyll “CoMe on, Cousin, See Mike over By Al and Cleo” “C. Hopkins Café Mmm, good!”

ElementRequirementFunctions N (nitrogen)21 g/m 3 Amino acids, nitrogenous bases, vitamins P (phosphorus)5 Nucleic acids, phospholipids, ATP, enzyme cofactor K (potassium)16 Ion balance, enzyme cofactor S (sulfur)10 Cysteine and methionine, vitamins Mg (magnesium)7 Chlorophyll cofactor, enzyme cofactor Ca (calcium)7 Membrane permeability, pectin glue, enzyme cofactor Fe (iron)0.3 Cytochrome cofactor, enzyme cofactor Essential “macroelements” for plants “Plant Food” has N-P-K analysis = %N-%P-%K

ElementRequirementFunctions Mn (manganese)0.04 g/m 3 Enzyme cofactor B (boron)0.008 Enzyme cofactor, pollen tube attraction Cl (chlorine)0.008 Ion balance, cofactor Zn (zinc)trace Enzyme cofactor, hormone synthesis, DNA binding protein cofactor Cu (copper)trace Enzyme cofactor (polyphenol oxidase), plastocyanin cofactor Mo (molybdenum)trace Cofactor for nitrate reductase, nitrogen reductase (N 2 fixation) Ni (nickel)trace Cofactor for urease (for uptake of organic N source) Essential “microelements” for plants

MacroelementsMicroelements

©1996 Norton Presentation Maker, W. W. Norton & Company Radish seedlings have roots with long root hairs that increase the surface area for water and mineral uptake