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

Abstract

Olive tree productivity is highly responsive to radiation conditions, so understanding the responses of the developmental processes that determine yield, including inflorescence and flower differentiation, is essential 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 orientation and spacing. In an east-west-oriented olive 'Arbequina' hedgerow located in Toledo (Spain), inflorescences were sampled from both sides (south and north) of the hedgerow canopy, at heights of 0-0.4, 0.8-1.2 and 1.6-2.0 m above the soil. Floral quality was determined at different levels of morphogenetic organization: inflorescence, flower, and ovary. Daily irradiance intercepted during 1 month before flowering by each canopy position was estimated using a model. The more highly illuminated south side received 31% more irradiance overall than the north side. Upper-layer irradiance was greater than the bottom layer, 4.0 and 1.5 times for the north and south sides, respectively. Inflorescence flower number and perfect flower proportion were similar at different heights on the south side. In contrast, north-side upper-layer inflorescences had more total flowers and perfect flowers than at lower hedgerow heights. At each height, perfect flower proportion was higher on the south than north side, while the remaining traits were similar between sides. Ovary tissue size, observed in histological preparations, did not vary among heights on each side, but was higher on the south than north side due to endocarp size. Simulated irradiance at flowering explained 90% of the observed variation of perfect flower number per inflorescence. Overall, the results emphasize the importance of irradiance at different hedgerow sides and heights on olive floral structures.

Inflorescence Traits and Floral Quality Parameters in Promising Olive Clones (cv Leccino): Influence of the Canopy Position

“…In the EZ of clones L 1.3 and L 1.4, the inflorescence length ranged from 26.1-30.2 to 25.8-28.4 mm, whereas in the IZ values ranged from 20.0-25.1 and 23.7-24.2 mm, respectively (Table 1). These results are in accordance with those reported by Trentacoste et al [22,45] and Moreno-Alias et al [27], who observed significantly shorter inflorescences in the less illuminated canopy positions. Significant differences in rachis length among clones were assessed in 2018 when inflorescences sampled from L 1.9 were shorter than those from L 1.3 and L1.4.…”

“…On this matter, few studies have been carried out on olive. In Arbequina, a Spanish cultivar characterized by high-quality ovule development [34], the canopy position did not affect the ovule quality, so that this genotype has been suggested for hedgerows olive orchards [22,27]. The great biodiversity that characterizes the olive germplasm requires broadening investigations on the reproductive organ quality in specific genotypes.…”

“…The cultural intensification, requiring a modification of canopy size and shape [24][25][26], may alter the microenvironment with possible effects on the processes involved in the regulation of the floral organs' development. In this context, studies on the impact of solar radiation interception on floral organogenesis are still scarce and have been focused on few cultivars, mainly of the Spanish germplasm [22,27].…”

Urban Phytoarchitecture Design Options: Greenspace Orientation and Tree Species Intensification

“…Analysis of the relationship between radiation related to hedgerows' orientation and soil quality can help improve the design and management of olive hedgerows intended for oil production. Furthermore, Moreno-Alías et al, [28] confirmed the nature of olive trees that are very responsive to sunlight radiation, determining the quality of flowers. One of the determinants for obtaining sunlight radiation is the orientation of the hedgerows.…”

Planting Systems for Modern Olive Growing: Strengths and Weaknesses

“…Nevertheless, this hypothesis is supported by solid ecophysiological principles applied to tree shapes [5] and by the results of about 15 years of experimentation [122]. Among the ecophysiological aspects, the palmette's favorable surface/volume ratio, an essential training form to establish hedgerows, stands out compared to three-dimensional forms, such as the vase and the monocone [123]. The higher value of the surface/volume ratio in the palmette explains the greater interception and the better distribution of light in the canopy, with positive implications on total tree assimilation rate, productivity, and sustainability [38,48,124,125].…”