Sun and shade leaves of Olea europaea respond differently to plant size, light availability and genetic variation

Abstract

Summary1. Canopy plasticity, the expression of different leaf phenotypes within the crown of an individual tree has complex functional and evolutionary implications that remain to be thoroughly assessed. We hypothesized that it can lead to disparity in how leaves in different positions of the canopy change with allometric growth and population genetic structure. 2. Leaf phenotypes of the inner and outer canopy were estimated using eight morphological and physiological characters. All traits were measured under field conditions in six populations of Olea europaea and again in a common garden for a subset of the genotypes. The same populations were characterized genetically with amplified fragment length polymorphisms (AFLP) genomic scans. With these data, we investigated the extent to which leaf phenotypes change with plant size, genetic processes and in response to environmental conditions inside and outside the canopy. 3. The size of trees measured in the field was clearly associated with the phenotype of sun but not to that of shade leaves. The phenotype of sun leaves depended on both direct and diffuse light, while that of shade leaves was found to correlate only with diffuse radiation. Additionally, light availability inside the canopy was conditioned by the shape of external leaves, and increasing elongation of sun leaves led to higher radiation in the inner canopy. 4. The field phenotypes of both inner and outer canopy leaves were correlated with genetic variation among populations. Conversely, in the common garden, the different genotypes expressed a homogeneous sun phenotype, while phenotypic differences among populations remained apparent in shade leaves. 5. We conclude that, in agreement with our working hypothesis, canopy plasticity is both cause and consequence of the environment experienced by the plant and might lead to the differential expression of genetic polymorphisms among leaves. Furthermore, we propose that it can contribute to buffer abiotic stress and to the partition of light use within the tree crown.

PaCeQuant: A Tool for High-Throughput Quantification of Pavement Cell Shape Characteristics

“…Leaf size and shape are not solely determined by genetic variability but also change during development and adapt to environmental conditions (Sultan, 1995(Sultan, , 2000Cho et al, 2007;Bar and Ori, 2014). Phenotypic plasticity of leaf morphology helps plants to optimize sunlight harvesting, CO 2 gas exchange, and acclimatization to changing ambient temperatures (Nicotra et al, 2010;de Casas et al, 2011). Hence, understanding the cellular and molecular mechanisms of growth regulation is of central importance to improve plant yield, quality, and resource use efficiency.…”

The Improved Canopy Shading Model Based on the Apple Intercropping System (Case Study: Loess Plateau, China)

“…Shading treatment reduces the PAR (photosynthetically active radiation) for intercrops and changes the microclimate under the canopy, resulting in decreased photosynthesis and transpiration rates. However, the intercrops can adapt to the low light intensity with changes in chlorophyll and the intercellular CO 2 concentration [24][25][26]. The physiological characteristics and productivity of intercrops impacted by the changed microclimate need further investigation [38].…”

“…However, the canopy shading reduces the net photosynthetic rate of the leaves, as well as the initial light energy conversion rate of PSII, so that the photosynthesis of vegetable is affected [24]. Studies have shown that leaves become thinner, leaf area becomes larger, and stem height increases in shading conditions in order to improve the ability to absorb and capture light [25,26]. At the same time, the leaves absorb more light, which causes the chlorophyll a/chlorophyll b to decrease and the pore density to decrease.…”

The ecological adaptability of four typical plants during the early successional stage of a tropical rainforest

“…Because of being more exposed to excessive light, outer layers of the canopy suffer more drastic changes in the abiotic conditions than inner layers (Niinemets 2007). Plant leaves show different ecophysiological traits at different positions in the canopy (Casas et al 2011;Giorio & Nuzzo 2012). Without these structural protections, photoinhibition of photosynthesis is likely to be much greater, which leads to apparent reduction of daily carbon gain (Pearcy et al 2005).…”