Shade screen increases the vegetative growth but not the production in ‘Fino 49’ lemon trees grafted on Citrus macrophylla and Citrus aurantium L.

• High leaf temperature and light intensity in summer and spring cause photoinhibition in citrus trees.
• We studied the effects of 50% shade screen in lemon trees .
• Shade screen increased the leaf water-use efficiency (WUEphy = ACO2/Eleaf) by increasing ACO2.
• As consequence of this vegetative growth is increased but yield production is reduced in shaded-trees.
• Fruit quality is hardly affected by shade screen.

Spain is the second-largest lemon fruit producing country in the world. Approximately 80% of the lemon production occurs in the arid southeast (Murcia and Alicante) region of Spain. For citrus fruits, 50% shade screen reduces the leaf temperature and light intensity at midday in the summer and the spring in these areas, resulting in an increase in the photosynthetic leaf water-use efficiency (WUEphy = A/Eleaf). In this experiment, the effect of shading with Aluminet-50 screen (which reduces approximately 50% of the incident photosynthetically active radiation) on agronomical responses of ‘Fino 49’ lemon trees (Citrus limon (L.) Burm. fil.) grafted on two rootstocks, Citrus macrophylla and Citrus aurantium L., were studied. This study was conducted in Santomera (Murcia) over a 4-year period (2008–2011) on 7-year-old lemon trees. Shade screen increased the height, canopy perimeter and canopy volume compared to those under full sunlight. However, shading effect reduced fruit production. Trees under full sunlight produced a total of 81 and 45 kg/tree, while trees under shade produced 70 and 33 kg/tree of C. macrophylla and C. aurantium L., respectively. Shading affected the physical characteristics of C. macrophylla fruits because fruits from trees under shade had lesser fresh weight and smaller width compared to those under full sunlight.