The impact of UV radiation at high altitudes close to the equator on morphology and productivity of pea (Pisum sativum) in different seasons

Ultraviolet radiation (UV) is well known to affect plant growth and development and to vary with latitude and altitude. The knowledge about the effect of high UV levels at high altitudes close to the equator on plant productivity is scarce. By using UV-transmitting and UV-blocking films, the impact of solar UV on growth and production potential of commercial pea (Pisum sativum) was studied at a high (2800m above sea level (masl)) and a lower (1700masl) altitude in Ethiopia during the dry (January–March) and wet (April–June) seasons. Morphological characteristics like plant height and number of branches as well as flowering time were affected by UV. Compared to the UV-blocking film, under the UV-transmitting film plants were 15–19% shorter and produced more branches at both altitudes and seasons. The flowering was delayed 2–5days when exposed to UV but only minor differences were found in numbers of pods. Numbers of leaves and specific leaf area were important for pod number. These parameters were more affected by altitude and season than UV level. Also, stomatal conductance at lower altitude was affected by season and was very low (0.06–0.08mmolm−2s−1) during the dry season compared to wet season, irrespective of UV radiation. At higher altitude (2800masl) UV radiation increased stomata conductance. Thus, the effect of UV on conductance depends largely on the interaction with other environmental conditions. Maximal PSII efficiency (Fv/Fm) was lowest in the dry season at both altitudes and the lowest value (0.66) was measured on plants exposed to UV radiation at high altitude. In conclusion, UV radiation affects plant morphology, flowering time, Fv/Fm and leaf conductance, but other climate factors, like irradiance, temperature and vapour pressure deficit (VPD), have a stronger impact on productivity of pea than UV radiation.