Plant evolution?

Question

What new strucutres had to develop to allow plants to live on land e.g. new supporting structures
thanks

Answer 1

Most likely the stuctures they used to absorb nutrients from the water became roots attached to soil. I see this happening in plants living close to the water's edge with pseudo roots touching and then reaching into soil under the very shallow water. After that, a very gradual transition to living on the land with roots growing ever stonger in the soil.

Answer 2

Hmm... I'll try to give you a simple answer.

The first plants who managed to live on land were the Bryophytes. However, they're still kinda attached to the aquatic habitats, even if not directly. For istance, they need a certain level of humidity to live, otherwise they'd risk to lose their precious liquids.
Bryophytes had provided themselves with a thin cuticle (made of cutin) in order to reduce the risks I was talking of.
Yet, they were the first plants that had Stoma: in fact, they needed a way to allow the circulation of CO2 which was in the air inside the leaves, since they needed CO2 in order to activate the photosynthetic processes; this way is given by Stoma.

So:
>Protective cuticle
>Stoma

Anyway, the real novelty can be found in the following cathegory of plants, the Vascular Cryptogams. These plants developed some special roots (first roots) which allowed them to be firmly attached to the ground: that way, the plant could 'focus' itself in its vertical growth. And that's convenient, since a higher plant can catch sun rays more effectively and have more photosyntethic processes: in other words, more energy.

Yet there was a problem: plants had to create a new system in order to transport water and mineral salts (=sap) from the roots to all the plant (now it's much taller, remember?): that's why it invented the xylem and the floem (conduction tissues).

Since these plants could grow taller and do more photosynthetic processes, there was an extra amount of energy (starch): so they had to create other tissues to store it, that would be the parenchimatic tissues (cortex, pith and pith rays).

Clearly, in order to protect itself from any other eventual loss of water, these plants had to invent another type of protective layer: something very similar to cork is starting to form.

So, remember:

>Conduction Tissues (Floem and Xylem)
>Consequent Need of a Storage-Tissue (Parenchimatic Tissues)
>New Protective Cork-like Layer (besides epidermis)

These new tissues also help the plant to have support.

There are also other specific tissues of support among plants, even if they will start to appear later: anyway, they are known as the sclerenchimatic and collenchimatic tissues.