Canopy light heterogeneity drives leaf anatomical, eco-physiological, and photosynthetic changes in olive trees grown in a high-density plantation

Abstract

In the field, leaves may face very different light intensities within the tree canopy. Leaves usually respond with light-induced morphological and photosynthetic changes, in a phenomenon known as phenotypic plasticity. Canopy light distribution, leaf anatomy, gas exchange, chlorophyll fluorescence, and pigment composition were investigated in an olive (Olea europaea, cvs. Arbequina and Arbosana) orchard planted with a high-density system (1,250 trees ha(-1)). Sampling was made from three canopy zones: a lower canopy (<1 m), a central one (1-2 m), and an upper one (>2 m). Light interception decreased significantly in the lower canopy when compared to the central and top ones. Leaf angle increased and photosynthetic rates and non-photochemical quenching (NPQ) decreased significantly and progressively from the upper canopy to the central and the lower canopies. The largest leaf areas were found in the lower canopy, especially in the cultivar Arbequina. The palisade and spongy parenchyma were reduced in thickness in the lower canopy when compared to the upper one, in the former due to a decrease in the number of cell layers from three to two (clearly distinguishable in the light and fluorescence microscopy images). In both cultivars, the concentration of violaxanthin-cycle pigments and β-carotene was higher in the upper than in the lower canopy. Furthermore, the de-epoxidized forms zeaxanthin and antheraxanthin increased significantly in those leaves from the upper canopy, in parallel to the NPQ increases. In conclusion, olive leaves react with morphological and photosynthetic changes to within-crown light gradients. These results strengthen the idea of olive trees as "modular organisms" that adjust the modules morphology and physiology in response to light intensity.

Environmental Regulation of Heterosis in the Allopolyploid Arabidopsis suecica

“…Our data are thus consistent with the notion that the hybrid vigor advantage of the allopolyploid is preferentially realized in specific environmental conditions, in this case higher light intensities. On a typical overcast day, light levels are around 20 to 150 mmol m 22 s 21 (Tang et al, 1988), while on a sunny day, depending on shading or canopy cover, light intensities can be between 200 and 1,500 mmol m 22 s 21 or go even up to 2,000 mmol m 22 s 21 (Nobel, 2009;Larbi et al, 2015). A. suecica therefore is expected to accumulate more starch relative to its progenitor species in well-lit locations or during periods when there are more sunny than cloudy days.…”

The First Molecular Identification of an Olive Collection Applying Standard Simple Sequence Repeats and Novel Expressed Sequence Tag Markers

“…Among these, only a few have a large area of cultivation and a clear impact on the production of oil and table olives (Ilarioni and Proietti, 2014). But the availability of a large set of well characterized and highly different cultivars is critical to increase the ability to face new agronomical challenges (De Gennaro et al, 2012; Larbi et al, 2015) and future climatic constrains (Moriondo et al, 2013; Proietti et al, 2014; Tanasijevic et al, 2014), diversifying the gene pools, preserving unique genetic traits currently available (Bracci et al, 2011; Corrado et al, 2011; Potts et al, 2012; Klepo et al, 2013) and offering different sensory profiles of extra-virgin olive oils.…”

Olive genotypes cultivated in an adult high-density orchard respond differently to canopy restraining by mechanical and manual pruning

“…Indeed, up to now only two Spanish cultivars, Arbequina and Arbosana, and the Greek Koroneiki have been demonstrated to have vegetative (medium-low vigour, slow canopy growth) and productive (early bearing, high yield efficiency) parameters fitting this new cropping system (Camposeo et al, 2008;Camposeo and Godini, 2010;Connor et al, 2014). Several aspects of varietal behavior have already begun to be studied for this new cropping system in Mediterranean environments: productive and vegetative parameters (Camposeo et al, 2008;Tous et al, 2010,4;Farinelli 2011, 2014;Allalout et al, 2011;Moutier et al, 2011;Papachatzis et al, 2011;Larbi et al, 2015;Proietti et al, 2015), plant architecture (Rosati et al, 2013;Strippoli et al, 2013), light interception (Connor and Gómez-delCampo, 2013), soil management Russo et al, 2014), ecophysiology and irrigation (Proietti et al, 2012;Gómez-del-Campo, 2013;Vivaldi et al, 2013), harvesting time . So, varietal response to pruning is still a crucial topic to be investigated in order to supply information about the agronomic management of high-density oliveculture for different cultivated genotypes (Connor et al, 2014).…”