Climate in tropical highlands is characterised by thermal uniformity without marked seasonal or monthly, but only daily temperature fluctuations at all altitudes. With increasing elevation, temperature, partial gas pressure and rainfall decrease, while solar and especially UV radiation and wind increase. Low temperature is the main climatic factor retarding plant growth and constrains introduction of fruit species to higher elevations. Commercial deciduous fruit growing is reported up to 2800 m in Colombia. In apple, rest breaking and rest avoidance techniques are applied. UV-B radiation at high altitudes originates stunting effects. Plants adapt to high UV radiation by reducing their leaf area and increasing leaf thickness and synthesis of protective pigments. Fruits suffer from sunburn during high radiation periods, while anthocyanin in red-peeled varieties acts as a UV-radiation filter. Transpiration, photosynthetic rates and light saturation point are enhanced with increasing elevation, but high UV-B radiation can decrease net photosynthesis