A Positive Response of UV-B (280–320 nm) Enhanced Solar Radiation on the Growth and Physiological Activities of Mint (Mentha arvensis L.)

The changes in plant morphology, foliar characteristics and physiological parameters were studied in Menthaarvensis, an aromatic herb grown under UV-B (ultraviolet-B (280-320nm)) enhanced solar radiation (simulated to 6–24% O₃ (ozone) depletion). UV-B enhancement was found to induce positive photomorphogenetic changes by increasing the fresh and dry weights. The SEM (scanning electron microscope) analysis of abaxial and adaxial leaf surfaces showed more oil glands with high stomatal frequency under enhanced UV-B when compared with ambient control. On unit fresh weight basis, Chl (chlorophyll) a and b and total Chl were enhanced in addition to the non-photosynthetic pigments such as flavonoids and anthocyanins. Measurement of photosynthetic efficiency in terms of fluorescence induction kinetics confirms that an alteration or redistribution of photosystems had occurred in Mentha offering resistance against UV-B. On the whole, a positive response at the level of morphology and physiological parameters was observed in Mentha seedlings grown under UV-B enhanced solar radiation.