Apart from perchlorate treatment mentioned in @Chris's answer, there are some other methods which could be able to remove the perchlorate from the martian soil:
Rinsing the soil with water. Perchlorate dissolves in water.
Heating the soil. Perchlorate decomposes giving oxygen as byproduct.
Using perchlorate eating bacteria which produce oxygen as a ...
This question is rather broad so I will give a broad answer.
Plants on Mars will require similar things to plants growing on Earth. All of these things:
Appropriate dark periods*
Sufficient atmospheric pressure
An atmosphere containing carbon dioxide
Absence of toxic conditions such as high levels of radiation or ...
A mature tree consumes 48 pounds (22kg) of CO2 per year.
The 22 kg of CO2 is made of (((32 g O2 / 1 mole) / (44 g C02 / 1 mole)) * 22 kg CO2 =) 16 kg O2. Note that, by dimensional analysis, this calculation makes sense, but presumes 100% release of O2 in photosynthesis.
Thus, a mature tree produces ~16 kg O2 per year.
According to NASA, a human ...