Olive inflorescence and flower development as affected by irradiance received in different positions of an east-west hedgerow

Abstract

Olive lree productivity is highly respons1ve to radiation condit10ns, so understanding the responses of the developmental processes that determine yield, among these inflorescence and flower differentiation, is essenllal for orchard design and management This is particularly true in the new intensive hedgerow orchards, where radiation reception highly depends on canopy height and row onentation and spacing. In an E-W (East- West) oriented hedgerow (cv. Arbequina) located in Toledo (Spain), inflorescences were sampled from both sides (South (S) and North (N)) of the hedgerow canopy, at heights 0-0.4, 0.8- 1.2, and 1.6-2.0 m above the so1l. Floral quality was determined at diffe rent levcls of morphogenetic organization: inflorescence, flower, and ovary. Daily irradiance intercepted during flower development by each canopy posit10n was estimated using a model. The more highly illuminated S side received 28% overall more irradiance than the N side. Upper layer irradiance was greater than bottom )ayer, 4.1 and 1.8 times for N and S sides, respectively. lnflorescence structure, flower number and perfect flower proportion were similar at different heights on the S side. In contrast, N side upper !ayer inflorescences were longer and had more nodes, total flowers and perfect flowers than at lower hedgcrow heights. At cach height perfcct flower proportion was higher on the S than N side, whilc thc remaining lraits were similar belween sides. Ovary tissue sizes, observed in histological preparat10ns, did not vary among heights on each side, but was higher on the S than N side due to endocarp size. Simulated irradiance at flowering explained 88% of the observed variat1on of perfect flower number per inflorescence. Overall, the results emphasize the importance of irradiance at different hedgerow sides and heights on olive inflorescence and floral slructures.