How come plants haven't evolved into taking nitrogen from the air? They need the nitrogenous compounds to make chlorophyll in the chloroplasts. I know pea plants can do this, but how come not other plants? Air is a very good source of nitrgoen you know!

because in evolution, one does not get to pick anything. one may not even get the desirable or needed traits or abilities but that's when natural selection steps in.

 

i think just for once i'll play Sayonara and say: you suggest that evolution has a purpose or that there is something guiding it along to a desired outcome. not the case.

Well, I would think that plants that live in areas which have a low amount of nitrates in the soil, would have evolved over the billions of years so that they can take the nitrogen straight from the air!

Plants don't assimilate nitrogen from the atmosphere. They take it up through their roots, via a symbiotic co-evolutionary system with a bacterium called Rhizobium. These bacteria colonize the roots of legumous plants (such as pea and lentil) and form nodules. The bacteria fix nitrogen and export it from the nodules to the plant, and in return the plants provide the synthetic products of photosynthesis (sugars) for the bacteria. Co-evolution is a rich system of evolutionary complexity and is often observed in natural systems.

ok. Thanx alot for the info!

Foliar feeds of nitrogenous compounds also work, granted they need to bound as a compound in order for it to work in that way, but if a huge rain drop hits the soil and some splashes up onto a leaf, be in no doubt that the plant can use )

Fungi are also used by plants in a similar way as bacteria in rhizobium, called mycorrhizae (which means 'fungus root'). Rhizobium mainly associate with legumes, and legumes are very good at nitrogen fixation, but mycorrhizae associate with nearly all plants.

Plants don't assimilate nitrogen from the atmosphere. They take it up through their roots, via a symbiotic co-evolutionary system with a bacterium called Rhizobium. These bacteria colonize the roots of legumous plants (such as pea and lentil) and form nodules. The bacteria fix nitrogen and export it from the nodules to the plant, and in return the plants provide the synthetic products of photosynthesis (sugars) for the bacteria. Co-evolution is a rich system of evolutionary complexity and is often observed in natural systems.

 

 

aka - symbiosis

Wow! thanx alot for the info guys! one more question:

 

They take it up through their roots, via a symbiotic co-evolutionary system with a bacterium called Rhizobium.

 

Is that the nitrogen fixing bacteria?

Yeah ones that convert N2 to NH3.

ok. Thanx!