answer this bio q?

Question

In an experiment on photosynthesis, a student fixed a strip of black paper on the
dorsal surface of a Bougainvillea leaf in the morning. In the evening she tested
the leaf for starch. The result was
(a) the dorsal surface of the leaf was white but the ventral surface turned blue.
(b) both the surfaces of the covered portion remained white.
(c) the entire leaf turned blue black.
(d) the entire leaf remained white.

Its urgent Also tell"what is the meaning of dorsal"

ANswer given by my teacher was (c)
I dont understand

Answer 1

Your teacher has given 'C' as the correct answer.

Let us see how is it correct.

When you test a leaf for starch formed in photosynthesis; it is mandatory to ' DESTARCH' that leaf first.( It is better and easier to destarch the entire plant.)

For this the plant concerned is kept in a photographic dark room for a few days.

At the same time it must not turn yellow due to lack of light. One has to be careful as to how many days you can put it in the dark.

Select a small potted plant as it usually has less starch reserve and becomes destarched earlier with out etiolation of the green pigment , the chlorophyll.


Every day a leaf is tested for starch . When it is tested negative for starch then it is ready for the test that was performed by that student in your question.


It seems that he did not do destarching and the teacher knew it . The entire leaf will turn blue as entire leaf has starch in it.

Now for dorsal and ventral surface of a LEAF.

The surface that receives the sun light directly is the UPPER or DORSAL surface .

The opposite is the ventral or lower surface.

For example one says that stomata are less on the dorsal but more on the ventral or lower surface.

http://www.pssc.ttu.edu/pss1321/images/33cpa1B.gif

http://fig.cox.miami.edu/Faculty/Dana/leaf.jpg

http://www.pssc.ttu.edu/pss1321/Web%20topics/cpa1B.htm

Answer 2

Your teacher has given 'C' as the correct answer.

Let us see how is it correct.

When you test a leaf for starch formed in photosynthesis; it is mandatory to ' DESTARCH' that leaf first.( It is better and easier to destarch the entire plant.)

For this the plant concerned is kept in a photographic dark room for a few days.

At the same time it must not turn yellow due to lack of light. One has to be careful as to how many days you can put it in the dark.

Select a small potted plant as it usually has less starch reserve and becomes destarched earlier with out etiolation of the green pigment , the chlorophyll.


Every day a leaf is tested for starch . When it is tested negative for starch then it is ready for the test that was performed by that student in your question.


It seems that he did not do destarching and the teacher knew it . The entire leaf will turn blue as entire leaf has starch in it.

Now for dorsal and ventral surface of a LEAF.

The surface that receives the sun light directly is the UPPER or DORSAL surface .

The opposite is the ventral or lower surface.

For example one says that stomata are less on the dorsal but more on the ventral or lower surface.

http://www.pssc.ttu.edu/pss1321/images/3...

http://fig.cox.miami.edu/faculty/dana/le...

http://www.pssc.ttu.edu/pss1321/web%20to...

Answer 3

answer is (a)

The region covered with black paper will not give test for starch as black paper prevents sunlight from entering that region of leaf.hence prevents photosynthesis.

Dosal surface means backside of leaf ie surface which is not brightly colored.

Answer 4

What makes you think I give two shiitts about biology??? I never claimed to be an expert in science. Why do you keep asking such moronic questions??

Answer 5

a