Bryophytes

[caite]

Why is it that bryophytes survive best in moist and shady habitats?

[victor]

Because they 'ancentors' live in water (thallophyta) and their modern types are living on the ground (Chormophyta)...so maybe Bryophyta is in the middle..and the reason is Bryophyta still classified into low degree plant so they still don't have any transport systems like xylem and phloem yet.

[ERS]

Victor is on the right path. The key is that Bryophytes are non-vascular and a moist surface is excellent for gas exchange and keeping the plant hydrated. If the plant was out in the heat of the sun, the surface wouldn't stay moist, so the plant wouldn't have water... And yes, bryophytes are considered to be a lower order of plant, than say the flowering plants.

Does this help?
ERS

[MrMistery]

That is true. Also, Briophites are dependent on water for fecundation. But the main reason is the lack of vascular tissues

[victor]

oh, yes I wanna ask...we know that plants if placed in dark place, they'll grow faster as the reaction of the Auksin hormone. would Briophytes do the same?

[MrMistery]

well, i know something that is kinda like that, but not quite the same. At superior plants: auxin is sintetised in the apical meristem and migrates to the darkened parts of the plant, causing elongation of the cells. Superior plants will not grow better if they are in the shade because they need light for photosynthesis.
Briphytes, however, only grow in shady areas because they need a lot of water. In direct sunlight, water evaporates. But this has nothing to do with auxin

[victor]

So, you try to say that bryophytes don't produce auxin? I would think the same also since bryophytes is not a khormophytes yet...

[MrMistery]

I don't know if you know this vut auxin is translocated through the phloem. Briophites have no phloeam or xilem so there is no point in producing auxin, now is there?!

[victor]

Yup..Bryophytes don't have any xilem or phloem and the question is..where do the auxin produced?do Bryophytes have it??

[mothorc]

so what do you think if someone have a callus of bryophytes <i>in vitro</i>

[MrMistery]

I do not think briophites have auxin. It would be a useless thing since briophites do not fototropism and gravitropism. Think of it: Have you ever seen a giant briophite? No, they stai the same size. That is because they can not grow any bigger(lack of xilem and phloem). each organ grows according to it's genetic code and that's it.
Of course this is only my opinion, I haven't been able to find this in any of my books.
PS: The synthesis of auxin is activated by light, one more reason of how illogical it would be for briophites to have it

[mothorc]

"It would be a useless thing since briophites do not fototropism and gravitropism"
Most of parasite plant have this characteristic.(I don't mean all sp in Bryophytes is parasite) . but "low degree revolution plant" is not shows anything about auxin, some bacteria have phytohormones also, and auxin is a large of substances have the same indol cycle structure.
I will ask my teacher about this problem.
To mystery: I think you read a lot of plant book, so can you give me some good title
Thanks a lot