The breath of a one-year-old mango tree increases after one year. In this way, with the increase in age, its breath also increase. Breath of a mature root and stem is increased by secondary growth (lateral growth). Usually, secondary growth occurs in gymnosperms and dicot plants. So all the broader plants of the world either gymnosperm or dicot plant.
Examples of gymnosperms are Cycas and Pinus. Mangos, Jamboline, Litchi, Shaal, Garjan, Sunday, Teak, Gamari, Karai etc. are examples of dicot plants.
How the increase in breath take place
Increase in breath takes place in root and stem by their secondary growth in the intrastellar or extrasolar region. First in the interstellar region of vascular bundles there develops a cambium ring. This cambium ring produces secondary xylem tissue towards the centre and secondary phloem tissue towards the periphery.
As many secondary xylem and secondary phloem are formed from the cambium ring so much increase the breath. Secondary growth also takes place in the extrastelar region (outside the pericycle).