MACROSCALE: MACROSCALE: EVAPOTRANSPIRATION THIS WEEKS LAB: UP AGAINST GRAVITY ! THIS WEEKS LAB: UP AGAINST GRAVITY ! HOW DOES WATER GET TO THE TOP OF A PLANT?

MICROSCALE 1 meter inches 1 millimeter (1mm) =.001 m 1 micron (1 um) =.001 mm 1 nanometer (1 nm) =.001 um = 1 x m (1 billionth of a meter) Stomata & guard cells !

Rooted in one spot………...no eyes…….. no ears…….. no nose……no brain…. DO PLANTS “SENSE” AND “RESPOND” TO THEIR ENVIRONMENT? HOW? WHAT WOULD IT BE IMPORTANT FOR PLANTS TO SENSE? LIGHT? GRAVITY? WIND/TOUCH? PATHOGENS

PLANTS SENSE THEIR ENVIRONMENT, AND THEY RESPOND BY: ANIMALS SENSE THEIR ENVIRONMENT, AND THEY OFTEN RESPOND BY: ACTION OR MOVEMENT …..………….CHANGING THEIR GROWTH PATTERN INDETERMINATE GROWTH ! DO PLANTS SENSE LIGHT? IF SO, HOW?

What do plants respond to? Light – phototropism Water – hydrotropism Gravity - geotropism Chemicals – chemitropism –P–Plant growth substances

SUNLIGHT Is made up of different wavelengths of light. When combined, they look white to the eye. When refracted by different amounts, we see different colors which represent the different wavelengths. prism

LIGHT IS COMPRISED OF MANY WAVELENGTHS EACH COLOR HAS ITS OWN WAVELENGTH High Energy Low Energy Electromagnetic spectrum

PLANTS USE PARTICULAR WAVELENGHS OF LIGHT FOR PHOTOSYNTHESIS CHLOROPHYLL A & B: absorb blue light (450 nm), absorb red light ( ) reflects green light (plants appear green to the eye) Infrared far red

PLANTS ABSORB LIGHT FOR PHOTOSYNTHESIS BUT HOW DO THEY SENSE IT?

COLEOPTILE IN MONOCOTS (GRASS, CORN) HOLLOW, CYLINDRICAL STRUCTURE PROTECTS PRIMARY LEAF AS IT PUSHES THROUGH THE SOIL primary root HOW CAN WE STUDY LIGHT PERCEPTION IN PLANTS? Coleoptiles have been used in experiments to learn about how plants sense light.

Darwin’s coleoptiles 1881 Blue light (450 nm) Coleoptile bends FULL LIGHT SPECTRUM PHOTOTROPISM IS A RESPONSE TO BLUE LIGHT !! WHAT DO PLANTS SEE? PHOTOTROPISM – a directed movement in response to light positive = towards light negative = away from light no response for others BLUE LIGHT IS ALSO USED IN PHOTOSYNTHESIS PLANTS SENSE BLUE LIGHT AND BEND TOWARD IT Test different wavelengths of light

SIMPLE APPARATUS FOR STUDYING COLEOPTILES CAMERA COLEOPTILES GO IN HERE & LIGHT FILTERS

SOME PLANTS PREFER SHADE SOME PLANTS PREFER FULL SUN WHAT OTHER RESPONSES DO PLANTS HAVE TO LIGHT ? SHADE HAS MORE FAR-RED LIGHT ----WHY? More red light ( nm)

Far red light = nm, more in shade Red light = nm, more in sun HOW DO PLANTS RESPOND TO FAR-RED LIGHT (indicates shade)? MORGAN & SMITH EXPERIMENTS Light wavelengths for photosynthesis were constant HOW WILL PLANTS RESPOND? H 0 : sun and shade plants respond the same H a : sun and shade plants respond differently What should we measure? Stem growth?

WHAT DO THESE RESULTS TELL US ? RESPONSE OF SHADE PLANTS ? RESPONSE OF SUN PLANTS? AT LEAST SOME PLANTS CAN SENSE FAR RED LIGHT SUN PLANTS RESPOND BY ELONGATING THEIR STEMS FASTER DATA INTERPRETATION CONCLUSIONS? SUN PLANTS SHADE PLANTS

BEANS ARE SUN PLANTS “ESSENTIALLY GROWING OUT OF THE SHADE”

How do plants know when to Flower? CAN PLANTS TELL THE LENGTH OF A DAY OR NIGHT? Spring Summer Fall Winter PHOTOPERIODISM – a response based on relative day and night length

bloom in summer bloom in fall Plants appear to sense the length of the NIGHT How could we test this?

HOW DO FAR-RED (735 nm) & RED LIGHT (660 nm) AFFECT FLOWERING? The Red/Far Red Switch RED has an effect FAR RED turns off effect

How do RED light and FAR-RED light affect the germination of lettuce seeds? Experiment: lettuce seeds need light to germinate. Good test system ! Red light promotes germination (ON) Far-red light inhibits germination (OFF) Last wavelength determines response ON-OFF SWITCH ! Red Far-red In nature, FAR RED tells the plant it is in the SHADE!

WHAT’S THE MECHANISM ? HOW DO PLANTS SENSE LIGHT? THERE IS A LIGHT SENSING MOLECULE = PHYTOCHROME THAT CHANGES ITS SHAPE = PHOTOREVERSIBLE ! not chlorophyll ! conformation RED: ON! GO!FAR RED: OFF! STOP! More Pr inhibitsMore Pfr stimulates

In sunlight, red dominates & is absorbed by the seed Weed/lettuce seeds germinate in light. Red light

Far-red light Lettuce seeds don’t germinate in the shade OFF SWITCH ! Relative amounts of: red: far-red

THE HUNT FOR PHYTOCHROME BUTLER 1959 CORN STEMS ELONGATE IN FAR-RED LIGHT Scientists ISOLATED PROTEINS ONE WAS PHOTO-REVERSIBLE ! PHYTOCHROME WAS DISCOVERED !

ChlorophyllAbsorbs blue and red light for photosynthesis Phytochromesenses red or far-red light & can affect: flowering seed germination stem elongation stomata opening? Phototropins in cell membrane of shoots sunlight detector Responds to blue light phototropism (by phosphorylation) Many other pigments in plantsabsorb other wavelengths of light & plant responds Pigment wavelength Senses shade Photoperiodism in chloroplasts PLANTS ARE CREATURES OF LIGHT ……………………… NEW

HOW DOES THIS TRANSLATES INTO A PLANT RESPONSE? A “HOT TOPIC” OF INVESTIGATION NOW ! 1.SIGNAL -- BLUE LIGHT 2.NPH1 PROTEIN CHANGES 3.PO 4 2- ADDED (PHOSPHORYLATION) (get activation) 4. CELL RESPONSE PHOTOTROPINS: SENSE BLUE LIGHT THEN WHAT?

PLANTS ARE CREATURES OF LIGHT, GRAVITY, AND FORM…….. WE WILL DISCUSS GRAVITY NEXT !