[Ose90 (OP)]

Dear Sirs and Madams,
I would be grateful if you clarify my doubts below:

1)How does tracheids overlap with each other? Are their slope parts of their tappered ends covering each other(do not extend beyond the edge), connecting through pits? Are all those pits found on the end walls of the tracheids bordered pits? Can they be simple pit?

2)What makes tracheid an inefficient water transport agent compared to vessel elements? My lecturer said it is because of the presence of flowing resistance. I agree with that but how it works? Is it because of the torus in the bordered pits which prevents water from entering the cell? Or is it because of the diagonal upward movement of water (In vessel elements, water is pulled upwards in a channel, so it is very efficient as their is hardly any resistance other than gravitational pull)?

3)Here are some questions regarding vessel elements. Firstly, I would like to ask what actually causes the differences in the types of lignification? What I have learnt is that these differences are caused by the rate of elongation of the stem.

Let me explain how it works and correct me if I'm mistaken.

Firstly, for young plants, their growth rate is high and hence, the xylem vessels in the protoxylem have high elongation rate, causing annular and spiral lignification which are flexible,long and thin. And as the plant grows older, their rate of growth starts becoming slower. This results in the decrease of rate of elongation of vessel systems in metaxylem.As a result, the diameter of the vessel systems becomes larger and their height is shorter,causing the scalariform, reticulate and pitted lignification.

Again, I would be glad if you can help me with this.

Thanks in advance,
Ose

[Ose90 (OP)]

anyone? I would really be grateful if you can clear my doubts, thank you!

[EvilFrog]

Hey! EvilFrog also got the same question.... anyone can explain?

[Don_1]

You might like to read this http://www.biologie.uni-hamburg.de/b-online/e06/06b.htm There are 4 pages on this site.

The last paragraph of this site might also be of some use http://www.amjbot.org/cgi/content/full/93/10/1490