CSEC BIOLOGY MARCH 1, 2016 10DM MRS. HAUGHTON PHOTOSYNTHESIS CSEC BIOLOGY MARCH 1, 2016 10DM MRS. HAUGHTON

So far in Photosynthesis…. From previous classes, students should know: The definition for photosynthesis The word equation for photosynthesis The chemical equation for photosynthesis The light stage of photosynthesis The dark stage of photosynthesis

Today we will be doing…. At the end of the lesson, students should know Internal and external structures of the leaf for photosynthesis The fate of the products of photosynthesis Conditions necessary for photosynthesis Limiting factors of photosynthesis Importance of photosynthesis Minerals required by plants for proper growth

Light and Dark Stages

Internal and External Adaptations of the Leaf The leaf of a plant is the main site of photosynthesis and so is where most food is made for the plant. The leaf has many adaptations which make them well suited for photosynthesizing.

External Features (Outer features) Broad, flat, thin laminae Petiole or leaf stalk Laminae are spaced out around stems so they do not overlap and block sunlight.

Internal Features (Inner features) CO2 enters and O2 diffuse. Air spaces. Palisade cells (diffusion and numerous; closely packed).

Chloroplasts can move to trap as much sunlight as possible. Root hair cells absorb water from the soil. Xylem vessels carry water and minerals from roots to leaves.

Internal Leaf Structure

Leaf on the Plant

Section through the Leaf

Details of the Cells in the Leaf Section

Detail of One Mesophyll Cell

Inside the Leaf Again

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What Happens to the Products of Photosynthesis? The oxygen produced by photosynthesis will diffuse into the atmosphere for animals to breathe. But the Glucose, which is the main product, is a very important starting material for all the other nutrients a plant needs.

The excess glucose that is made during photosynthesis is stored as the starch grains in the chloroplasts

Conditions Necessary for Photosynthesis Carbon dioxide (diffuses into leaf through stomata). Water (absorbed from soil by roots). Sunlight energy (absorbed by chlorophyll). Chlorophyll (green pigment in chloroplasts).

Enzymes (present in chloroplasts). Mineral elements (absorbed from soil by roots). Correct temperature (0°C to 40°C for enzymes).

Limiting Factors of Photosynthesis The following are substances and situations that when varied can change how quickly photosynthesis occurs. They are called limiting factors since they each can slow down the rate of photosynthesis if they are in lower or smaller amounts than the other variables.

Light: limits the rate at dusk and dawn and during winter and fall months. Carbon dioxide: limits the rate during the day in most climates. Temperature: limits the rate during the winter.

Water: limits the rate when water levels are low. Wavelength of light: the rate of photosynthesis is affected by the wavelength of light. Photosynthesis is fastest in blue and red light and slowest in green and yellow light.

Wavelength for Photosynthesis

Importance of Photosynthesis Photosynthesis is directly related to the life and survival of all the other living creatures on earth. It supplies oxygen for animals. It is the way that sunlight energy is used by plants to make different nutrients that can animals can obtain by eating the plants. It supplies energy to plants which they pass on to animals when eaten.

Minerals Required by Plants for Proper Growth