This slide presentation is about life processes in plants and animals but specifically focuses on plant responses to the environment (Grade 12).

1. LIFE PROCESSES IN PLANTS AND ANIMALS
PLANT RESPONSES TO THE ENVIRONMENT by Michael Ndhlovu
GRADE 12

2. INTRODUCTION
PLANT HORMONES ARE RESPONSIBLE FOR GROWTH AND
RESPONSES TO EXTERNAL STIMULI.
ALL PLANTS BELONG TO THE KINGDOM PLANTAE (MOTSOKO,
2022).
GIBERELLINS, AUXINS, CYTOKININS, ABSCISIC ACID, AND
ETHYLENE ARE THE FIVE MAIN GROUPS OF PLANT GROWTH
SUBSTANCES.
RESPONSES TO EXTERNAL STIMULI AND GROWTH IN PLANTS
OCCURS THROUGH TROPISMS (FERGUSON, 2012).
TROPISMS ARE SLOW PLANT MOVEMENT RESPONSES EITHER
AWAY OR TOWARDS A STIMULUS.
MOVEMENTS AWAY FROM THE STIMULUS ARE NEGATIVE
TROPISMS.
MOVEMENTS TOWARDS THE STIMULUS ARE POSITIVE TROPISMS.

3. TYPES OF TROPISMS IN PLANTS
PHOTOTROPISM – PLANT GROWTH IN RESPONSE TO LIGHT.
GEOTROPISM – PLANT GROWTH IN RESPONSE TO GRAVITY.
NASTIC MOVEMENT – THE CHANGE IN THE POSITION OF THE
LEAVES & PETALS.
STOMATAL OPENING/CLOSING – THE OPENING & CLOSING
OF THE STOMATA DUE TO PHOTOSYNTHETIC & RESPIRATION
PRODUCTS (MOTSOKO, 2022).
THE THREE MAIN PLANT HORMONES THAT YOU’LL LEARN
ABOUT ARE...

4. AUXINS, GIBERELLINS & ABSCISIC ACID
HORMONE EFFECT
AUXINS -APICAL DOMINANCE
-PREVENTS LEAVES FROM WILTING/DYING &
KEEPS FRUITS ATTACHED TO PLANTS.
-ENLARGEMENT OF CELLS, DIFFERENTIATION,
GROWTH & CELL DIVISION.
-PHOTOTROPISM & GEOTROPISM.
GIBERELLINS -IS RESPONSIBLE FOR SEED GERMINATION,
FLOWERING & DEVELOPMENT.
-CONTROLS STEM ELONGATION, ALLOWING
PLANTS TO GROW TALLER.
ABSCISIC ACID -ALLOWS LEAVES & FRUITS TO DETERIORATE.
-CLOSES STOMATA.
-SLOWS DOWN GROWTH.

5. PHOTOTROPISM
PHOTO MEANS LIGHT, THEREFORE,
PHOTOTROPISM IS A TYPE OF GROWTH THAT
OCCURS IN RESPONSE TO A LIGHT STIMULUS
(FERGUSON, 2012).
TYPES OF PHOTOTROPISM
POSITIVE PHOTOTROPISM – THE GROWTH OF
STEMS TOWARDS LIGHT.
NEGATIVE PHOTOTROPISM – THE GROWTH OF
ROOTS AWAY FROM LIGHT.

6. GEOTROPISM
THE PREFIX ‘GEO’ MEANS EARTH, AND
GEOTROPISM IS A TYPE OF PLANT GROWTH
OR MOVEMENT THAT OCCURS IN RESPONSE
TO GRAVITY (FERGUSON, 2012).
TYPES OF GEOTROPISM
POSITIVE GEOTROPISM – ROOT GROWTH
TOWARDS THE FORCE OF GRAVITY.
NEGATIVE GEOTROPISM – SHOOT GROWTH
AWAY FROM THE FORCE OF GRAVITY.

7. WEED CONTROL USING HORMONES
PLANT HORMONES CAN BE NATURAL OR MAN-
MADE, ALSO KNOWN AS SYNTHETIC.
THEY ARE USED IN AGRICULTURE,
HORTICULTURE, & BIOTECHNOLOGY. THEY ARE
WIDELY USED FOR WEED CONTROL.
THEY ARE A SAFE AND SUSTAINABLE WAY OF
CONTROLLING WEEDS.
AUXINS ARE SOME OF THE HORMONES USED
FOR WEED CONTROL.

8. PLANT DEFENCE MECHANISMS
JUST LIKE MOST TERRESTRIAL AND AQUATIC
ORGANISMS, PLANTS ALSO HAVE DEFENCE
MECHANISMS THAT THEY USE TO PROTECT
THEMSELVES FROM BEING EATEN BY ANIMALS
(HERBIVORES AND OMNIVORES), OR INVADED BY
PATHOGENS.
THEY USE THEIR RESOURCES (WATER AND
MINERALS) FOR DEFENCE AND GROWTH.
AS DEFENCE MECHANISMS, SOME PLANTS MAKE
EXTERNAL OR INTERNAL SUBSTANCES.
THESE CAN BE CHEMICALS THAT HAVE A BITTER
TASTE AND UNPLEASANT SCENTS, OR THORNS.

9. PLANT DEFENSE MECHANISMS
CONTINUED….
THORNS ARE THE MOST
COMMON DEFENSE MECHANISM
USED BY PLANTS.

10. QUICK FACTS ABOUT PLANTS!!
PLANTS BELONG TO THE KIGDOM PLANTAE (MABOPE,
2022).
ACCORDING TO MNGWE (2022) PLANTS ARE KNOWN AS
AUTOTROPHS BECAUSE THEY CAN MAKE THEIR FOOD
THROUGH PHOTOSYNTHESIS, WHICH IS A CHEMICAL
PROCESS WHEREBY PLANTS MAKE THEIR OWN FOOD
USING GLUCOSE, RADIANT ENERGY, CARBON DIOXIDE,
AND NUTRIENTS FROM THE SOIL.
ORGANISMS THAT MAKE THEIR OWN FOOD ARE CALLED
PRODUCERS.
PLANT EATING ANIMALS ARE CALLED HERBIVORES AND
ARE CONSUMERS SINCE THEY CANNOT MAKE THEIR
OWN FOOD (JASON, 2022).

11. THE END!

12. REFERENCE LIST
JASON, TV. (2022). ANIMAL NUTRITION. AVAILABLE FROM SLIDESHARE AT:
https://www.slideshare.net/TeslinVenusJason
MABOPE, A. (2022). HETEROTROPHS AND AUTOTROPHS. AVAILABLE FROM
SLIDESHARE AT: https://www.slideshare.net/AmahleMabope
MNGWE, T. (2022). CELLULAR RESPIRATION. AVAILABLE FROM SLIDESHARE AT:
https://www.slideshare.net/Thabisile15
MOTSOKO, K. (2022). PHOTOSYNTHESIS. AVAILABLE FROM SLIDESHARE AT:
https://www.slideshare.net/Kgotsofalang
FERGUSON, S. (2012). PLANT RESPONSES TO THE ENVIRONMENT. AVAILABLE AT:
https://www.slideshare.net/Sianfergs/plant-responses-to-the-environment