I will review basic plant structure and investigate stomata. 11.28.16 Catalyst What adaptations allow plants to maintain their water on land? I will review basic plant structure and investigate stomata.

The week…

EXPERIMENT RESULTS CONCLUSION Figure 39.5 In 1880, Charles Darwin and his son Francis designed an experiment to determine what part of the coleoptile senses light. In 1913, Peter Boysen-Jensen conducted an experiment to determine how the signal for phototropism is transmitted. EXPERIMENT In the Darwins’ experiment, a phototropic response occurred only when light could reach the tip of coleoptile. Therefore, they concluded that only the tip senses light. Boysen-Jensen observed that a phototropic response occurred if the tip was separated by a permeable barrier (gelatin) but not if separated by an impermeable solid barrier (a mineral called mica). These results suggested that the signal is a light-activated mobile chemical. CONCLUSION RESULTS Control Darwin and Darwin (1880) Boysen-Jensen (1913) Light Shaded side of coleoptile Illuminated Tip removed Tip covered by opaque cap covered by trans- parent cap Base covered by opaque shield Tip separated by gelatin block by mica Figure 39.5

Went concluded that a coleoptile curved toward light because its dark side had a higher concentration of the growth-promoting chemical, which he named auxin. The coleoptile grew straight if the chemical was distributed evenly. If the chemical was distributed unevenly, the coleoptile curved away from the side with the block, as if growing toward light, even though it was grown in the dark. Excised tip placed on agar block Growth-promoting chemical diffuses into agar block Agar block with chemical stimulates growth Control (agar block lacking chemical) has no effect Control Offset blocks cause curvature RESULTS CONCLUSION In 1926, Frits Went’s experiment identified how a growth-promoting chemical causes a coleoptile to grow toward light. He placed coleoptiles in the dark and removed their tips, putting some tips on agar blocks that he predicted would absorb the chemical. On a control coleoptile, he placed a block that lacked the chemical. On others, he placed blocks containing the chemical, either centered on top of the coleoptile to distribute the chemical evenly or offset to increase the concentration on one side. EXPERIMENT Extracted the chemical messenger for phototropism, auxin, by modifying earlier experiments

Hormones chemical signals that allow an organism to respond/grow and develop

Hormone Redux. Auxin – stimulates growth, formation and branching of roots. Cytokinins – lateral cell division Gibberellins – stem elongation, fruit growth, seed germination Abscisic Acid (ABA) – slows down growth for dormancy, closes stomata when plant is stressed Ethylene – fruit ripening, ageing and death. ** Remember, you are an expert on one of these. ***

Land. Struggles. Surviving. Less water, so plants needed to avoid drying out No support against gravity Surviving. Cuticles Vascular tissue Roots Leaves

Seeds! MULTI-CELLULAR RESISTANT DORMANCY DISTANCE FAVORABLE CONDITIONS

Angiosperms WHY?!? aka flowering plants flowers and fruits Are the most widespread and diverse of all plants WHY?!?

The Root System Underground (usually) Anchor the plant in the soil Absorb water and nutrients Conduct water and nutrients Food Storage

The Shoot System Above ground (usually) Elevates the plant above the soil Many functions including: photosynthesis reproduction & dispersal food and water conduction ** the shoot system includes the leaves and the reproductive organs

Tissues.

Transport Phloem Transports food (sugars) and other items Xylem Transports water and minerals

Make & Support Parenchyma Plant metabolism Most with chloroplasts Sclerenchyma Dead cells with super thick cell walls that provide support Collenchyma - Living support cells.

11.29.16 Catalyst – What is the function of the stomata? I will compare stomata frequencies.

Stomata

Today Stomata Lab While you wait for the polish to dry… Prepare and analyze 3 samples Today’s goal – one leaf completed. Completed Lab due Friday While you wait for the polish to dry… Color code the leaf diagram

Hormones help plants maintain homeostasis Homeostasis – an organism’s ability to maintain a stable internal environment while the external environment changes

Tropism – when an organism responds to the environment’s stimuli Phototropism - light Thigmotropism – touch/contact Gravitropism – gravity