This adaptation is called apical growth - the tip of each part of the plant is the only part which will continue to grow indefinitely. It leads to long, branching structures which are well adapted for collecting as much light as possible, maximising the opportunities for photosynthesis.
However, this does lead to a problem. Out on the land, in order to 'fix' carbon dioxide, you can't just use the gas dissolved in the water. You aren't in the water any more. You need to open parts of your photosynthesising structures to let the carbon dioxide in before it dissolves in your internal water, where you can use it. But this means that you will lose water to the air through evaporation.
So far, as a small plant, it's been sufficient to allow water to migrate through you between your cells via a physical process called osmosis, in which water will migrate to the most concentrated part of the plant.
Unfortunately, osmosis is limited to fairly short distances and you have got a lot longer thanks to your apical growth adaptation.
One solution would be for some cells to reach maturity, thicken their cell walls with lignin and then die back, creating very fine tubes within you which can carry water by a combination of capillary action and osmosis.
You will sacrifice some cells, expend some energy making lignin, and be at risk of pumping any nasty chemicals throughout your system, but you will be able to photosynthesise more.
Tubes please.
No tubes.
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