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ORIENTATION RESPONSES IN PLANTS
ORIENTATION RESPONSES IN PLANTS
 Plants are autotrophs – making food from photosynthesis.
 Apart from reproductive organs (flowers) plant structure and functions are adapted for photosynthesis directly or
indirectly.
ORIENTATION RESPONSES IN PLANTS
 Plants are autotrophs – making food from photosynthesis.
 Apart from reproductive organs (flowers) plant structure and functions are adapted for photosynthesis directly or
indirectly.
 Unable to move from where they germinate, but can move leaves and stems.
ORIENTATION RESPONSES IN PLANTS
 Plants are autotrophs – making food from photosynthesis.
 Apart from reproductive organs (flowers) plant structure and functions are adapted for photosynthesis directly or
indirectly.
 Unable to move from where they germinate, but can move leaves and stems.
 Movements are much slower than animals because the cellulose cell wall of plant cells prevents repid change in
cell shape.
ORIENTATION RESPONSES IN PLANTS
 Plants are autotrophs – making food from photosynthesis.
 Apart from reproductive organs (flowers) plant structure and functions are adapted for photosynthesis directly or
indirectly.
 Unable to move from where they germinate, but can move leaves and stems.
 Movements are much slower than animals because the cellulose cell wall of plant cells prevents repid change in
cell shape.
 Plant movements are limited to changes in cell turgor (nastic responses) or growth (tropisms).
TROPISMS
 Growth responses – due to abiotic factors (light intensity, chemicals, gravity, water and touch).
TROPISMS
 Growth responses – due to abiotic factors (light intensity, chemicals, gravity, water and touch).
 Response to put the plant into favourable conditions and away from unfavourable.
TROPISMS
 Growth responses – due to abiotic factors (light intensity, chemicals, gravity, water and touch).
 Response to put the plant into favourable conditions and away from unfavourable.
 Eg – growth towards maximum light intensity for photosynthesis in a forest.
 https://www.youtube.com/watch?v=zctM_TWg5Ik
TROPISMS
 Positive phototropism – growth of a stem towards light.
 Positive gravitropism (aka geotropism) – growth of young root from the seed downwards. Anchoring the plants
and enabling uptake of water and nutrients.
TROPISMS
 Positive phototropism – growth of a stem towards light.
 Positive gravitropism (aka geotropism) – growth of young root from the seed downwards. Anchoring the plants
and enabling uptake of water and nutrients.
 Negative gravitropism – growth of the young shoot upwards towards the surface.
TROPISMS
 Positive phototropism – growth of a stem towards light.
 Positive gravitropism (aka geotropism) – growth of young root from the seed downwards. Anchoring the plants
and enabling uptake of water and nutrients.
 Negative gravitropism – growth of the young shoot upwards towards the surface.
 Positive hydrotropism – growth of roots towards a water source.
TROPISMS
 Positive phototropism – growth of a stem towards light.
 Positive gravitropism (aka geotropism) – growth of young root from the seed downwards. Anchoring the plants
and enabling uptake of water and nutrients.
 Negative gravitropism – growth of the young shoot upwards towards the surface.
 Positive hydrotropism – growth of roots towards a water source.
 Positive chemotropism – pollen tubes growing down a stigma towards the ovary is guided by chemicals. This
response ensures male gametes reach female gametes so fertilisation can occur.
TROPISMS
 Positive phototropism – growth of a stem towards light.
 Positive gravitropism (aka geotropism) – growth of young root from the seed downwards. Anchoring the plants
and enabling uptake of water and nutrients.
 Negative gravitropism – growth of the young shoot upwards towards the surface.
 Positive hydrotropism – growth of roots towards a water source.
 Positive chemotropism – pollen tubes growing down a stigma towards the ovary is guided by chemicals. This
response ensures male gametes reach female gametes so fertilisation can occur.
 Positive thigmotropism – growth of stem of climbing plants around a host plant.
 https://www.youtube.com/watch?v=pCFstSMvAMI