Tomato and sugarcane leaves are treated with radioactive ${}^{14}\text{CO}_{\text{2}}\text{.}$ In which compounds does radioactivity appear for the first time?
 

	Tomato	Sugarcane
1	RuBP	PEP
2	3-PGA	OAA
3	PGAL	Malic acid
4	Glucose	Pyruvic acid

In C₃ plants, the first stable product formed during photosynthesis is a three-carbon compound called 3-phosphoglycerate (3-PGA). Hence, radioactive carbon is inserted into this product. In C₄ plants, the first stable product formed during photosynthesis is a four-carbon compound called oxaloacetate.