Someone plz i have this question about environmental science and it’s due tommorow

In what for do plants utilize nitrogen? why do they need nitrogen?

Me with these questions image attached

In tomato plants, mendel found that the allele for smooth seeds (s) is dominant, while the allele for wrinkled seeds (s) is recessive. which of these punnett squares shows crosses between two plants heterozygous for smooth seeds? i need this to be answered as soon as ! sry the picture is bad quality