Plant Adaptations and Tropisms PDF

Plant Adaptations features / structures / behaviors of organisms to help them survive (and reproduce) in their env’t Physical Adaptation How does it help them survive? Darker leaves absorb more light; whereas leaves lighter in color will reflect more light Larger...

Plant Adaptations features / structures / behaviors of organisms to help them survive (and reproduce) in their env’t Physical Adaptation How does it help them survive? Darker leaves absorb more light; whereas leaves lighter in color will reflect more light Larger leaves ↑ SA to capture more light Waxy Cuticle Reduce water loss Thick Epidermis Reduce water loss Hairs Create a mini-windbreak that allows for a thick boundary layer of water vapor adjacent to plant 180px-Cap1033-botao1 Tropisms directional growth of a plant as determined by an environmental factor Positive tropism → grow toward the stimulus Negative tropism → grow away from the stimulus  “Turning” Types of Control systems to Tropism ensure survival Phototropism Gravitropism Thigmotropism Hydrotropism (nastic response) response response response to response to to water to light gravity contact Root tips negative moving Sunflower is a positive Closing of a highly gravitropism gravitropism towards phototropic carnivorous water plant - tracking Venus the movement shoots grow Flytrap leaf of the sun roots grow when it throughout the against gravity toward captures day. gravity prey  Types of Control systems to “Turning” Tropism ensure survival Phototropism Hydrotropism Gravitropism Thigmotropism (nastic response) response response response to gravity response to to water to light contact Root tips negative Closing of a moving Sunflower is a positive highly gravitropism carnivorous towards gravitropism phototropic Venus water plant - tracking the movement Flytrap leaf of the sun shoots grow roots grow when it throughout the against gravity toward captures day. gravity prey  Investigations of Phototropism Darwin & Darwin Growth but no Growth and covered the tip movement movement of emerging No growth nor movement cereal plant Confirmed that the tip was Growth and responsible for movement phototropism Boysen-Jensen proposed a chemical moving from tip is what allowed communication with area of elongation 1. cut tip and placed gelatin (allowed chemical to flow) 2. cut tip and inserted mica (did not allow chemical to flow) Chemical could still move to the Confirmed a chemical is tip present in the tip Went Confirmed that auxin is the chemical in the tip auxin is a hormone o a chemical compound made in one area and transported to another to stimulate the growth of new plant cells  Auxin moves away from the light Auxin spreads faster on the darker/shaded side Cells elongate on shaded size → causing uneven growth bending towards the light