PhotosynthesisPhotosynthesisThe Flow of Energy and MatterThe Flow of Energy and Matter

Nobody can really explain photosynthesis I’d like some super smart guy to explain how a little acorn becomes an oak tree. Where does it all come from?

Investment Bonds

I think most of it comes from nutrients in the soil that are taken up by the plant’s roots Or it could come from the

water taken up by the plant’s roots

What if it comes from molecules in the air that came in through holes in the plant’s leaves

I think most of it comes from the sun’s energy.

Are they just smarter than us?

Obviously

• Almost all plants are photosynthetic autotrophs

• So are some bacteria and protists– Autotrophs generate their own organic matter using inorganic matter

– Sunlight energy is transformed to energy stored in the form of chemical bonds

(a) Mosses, ferns, andflowering plants

(b) Kelp

(c) Euglena (d) Cyanobacteria

THE BASICS OF THE BASICS OF PHOTOSYNTHESISPHOTOSYNTHESIS

Light Energy Harvested by Light Energy Harvested by Plants & Other Photosynthetic Plants & Other Photosynthetic

AutotrophsAutotrophs

What Makes it Grow?What Makes it Grow?

The question of how plants feed was investigated in the 17th century by a Dutch scientist called Jan Baptist Van Helmont.

Putting on MassPutting on MassVan Helmont’s ExperimentVan Helmont’s Experiment 

 

““I took an earthen vessel, in which I put 200 pounds of I took an earthen vessel, in which I put 200 pounds of earth that had dried in a furnace, which I moistened with earth that had dried in a furnace, which I moistened with rainwater, and I implanted therein the trunk or stem of a rainwater, and I implanted therein the trunk or stem of a willow tree, weighing five pounds. And at length, five years willow tree, weighing five pounds. And at length, five years being finished, the tree spring from thence did weigh 169 being finished, the tree spring from thence did weigh 169 pounds and about three ounces. … Lest the dust that flew pounds and about three ounces. … Lest the dust that flew about should be mingled with the earth, I covered the lip or about should be mingled with the earth, I covered the lip or mouth of the vessel with an iron plate covered with tin and mouth of the vessel with an iron plate covered with tin and easily passable with many holes. … I again dried the earth easily passable with many holes. … I again dried the earth up in the vessel, and there was found the same 200 up in the vessel, and there was found the same 200 pounds, wanting about two ounces.”pounds, wanting about two ounces.”

  

What Makes it Grow?What Makes it Grow?

.

• He took a small willow tree and planted it in a large pot of soil.

• Before he did this he carefully found the mass of the dry soil and the mass of the tree.

• He covered the soil with a lid so that nothing could fall onto the surface of the soil and add to its mass.

• There were holes in the lid so that the tree could grow out of the soil and so that air and water could reach the roots

What Makes it Grow?What Makes it Grow?

.

• Van Helmont left the tree for five years, giving it only rain water to drink.

• At the end of the five years he took the mass of the tree and the mass of the dry soil for a second time.

• The results of this experiment are shown below:

What Makes it Grow?What Makes it Grow?

.The tree had grown a lot, its mass had increased by just over 74kg. The soil, however, had only lost about 60 grams.

 

Mass kg  At start After 5

yearsChange in Mass

Tree 2.27 76.74 74.47Soil 90.72 90.66 0.06

Putting on MassPutting on MassVan Helmont’s ExperimentVan Helmont’s Experiment

 

• Was Van Helmont’s hypothesis supported?

 • Did the soil provide the

mass for the plant? Why or why not?

 • Does this change youryour

answer to the first question?

 

Putting on MassPutting on MassJohn WoodwardJohn Woodward

 

• Van Helmont thought that the tree must have grown from the rain water and that the soil had not given anything to the plant.

• A professor and physician at Cambridge University in the late 1600s, tried to design an experiment to test Van Helmont’s hypothesis that water was the source of the extra mass.

• In a series of experiments over as many as 77 days, Woodward measured the water consumed by plants.

Putting on MassPutting on MassJohn WoodwardJohn Woodward

• For example, one plant showed a mass gain of about 1 gram, while Woodward had added a total of almost 76,000 grams of water during the 77 days of plant growth

• This was a typical result.• Woodward correctly

suggested that most of this water was “drawn off and conveyed through the pores of the leaves and exhaled into the atmosphere. So the hypothesis that water is the nutrient used by plants was rejected.

Putting on MassPutting on Mass

•Does this change youryour answer to the first question?

Putting on MassPutting on MassJoseph Priestley English Joseph Priestley English

ChemistChemist The Interaction of Plants With Air

• August of 1771, Joseph Priestly put a sprig of mint into a transparent closed space with a candle.

• The candle burned and soon went out• After 27 days, he relit the extinguished candle

again and it burned perfectly well in the air that previously would not support it.

• And how did Priestley light the candle?

Putting on MassPutting on MassJoseph PriestleyJoseph Priestley

The Interaction of Plants With Air

• So how did the So how did the candle burn candle burn again after 27 again after 27 days?days?

• What happened What happened in the jar during in the jar during those 27 days?those 27 days? So, Priestly proved that So, Priestly proved that somehow plants somehow plants change the change the composition of the air.composition of the air.

Putting on MassPutting on MassJoseph PriestleyJoseph Priestley

In another celebrated Experiment from 1772, Priestley kept a mouse in a jar of air until it collapsed. He found that a mouse kept with a plant would survive. However, we do not recommend to repeat this experiment and hurt innocent animals.

Putting on MassPutting on MassJoseph PriestleyJoseph Priestley

These kinds of observations led Priestley to offer an interesting hypothesis that plants restore to the air whatever breathing animals and burning candles remove.

Putting on MassPutting on Mass

So what is the answer to the question:Where does the mass come Where does the mass come

from?from?