Olive fruit growth, tissue development and composition as affected by irradiance received in different hedgerow positions and orientations

Abstract

Incident radiation strongly influences fruit development, but little is known regarding the specific responses to the radiation differences found at different canopy heights and orientations in the new intensive hedgerow orchards. We tested the effect of position-determined solar microenvironment on olive fruit size, composition, and cellular development among positions at successive heights along both faces of N–S and E–W oriented olive hedgerows (cv. Arbequina). Total incident irradiance over the fruit growth period at each canopy position was modeled, and the relationships of all fruit parameters to irradiance and amongst each other were tested. Fruit and mesocarp weight and oil increased from canopy base to top and were linearly related to irradiance, while water content showed the opposite pattern, suggesting that priorities for distribution among different sinks are strongly influenced by irradiance level. Similar patterns of fruit size and composition in relation to irradiance were also observed among hedgerow orientations. Endocarp weight and composition varied little among irradiance levels, reflecting the conservative nature of this tissue as an active sink. Greater fruit size, mesocarp weight, and oil in positions of higher irradiance, even when fruit number was higher, indicating that those yield components were primarily affected by source supply and not limited by sink competition. Fruit exposed to light developed larger mesocarp cells than shaded fruit but cell number was not affected, and mesocarp oil content was highly associated with mesocarp cell size.