Hydraulic Traits Emerge as Relevant Determinants of Growth Patterns in Wild Olive Genotypes Under Water Stress

Abstract

The hydraulic traits of plants, or the efficiency of water transport throughout the plant hydraulic system, could help to anticipate the impact of climate change and improve crop productivity. However, the mechanisms explaining the role of hydraulic traits on plant photosynthesis and thus, plant growth and yield, are just beginning to emerge. We conducted an experiment to identify differences in growth patterns at leaf, root and whole plant level among four wild olive genotypes and to determine whether hydraulic traits may help to explain such differences through their effect on photosynthesis. We estimated the relative growth rate (RGR), and its components, leaf gas exchange and hydraulic traits both at the leaf and whole-plant level in the olive genotypes over a full year. Photosynthetic capacity parameters were also measured. We observed different responses to water stress in the RGRs of the genotypes studied being best explained by changes in the net CO2 assimilation rate (NAR). Further, net photosynthesis, closely related to NAR, was mainly determined by hydraulic traits, both at leaf and whole-plant levels. This was mediated through the effects of hydraulic traits on stomatal conductance. We observed a decrease in leaf area: sapwood area and leaf area: root area ratios in water-stressed plants, which was more evident in the olive genotype Olea europaea subsp. guanchica (GUA8), whose RGR was less affected by water deficit than the other olive genotypes. In addition, at the leaf level, GUA8 water-stressed plants presented a better photosynthetic capacity due to a higher mesophyll conductance to CO2 and a higher foliar N. We conclude that hydraulic allometry adjustments of whole plant and leaf physiological response were well coordinated, buffering the water stress experienced by GUA8 plants. In turn, this explained their higher relative growth rates compared to the rest of the genotypes under water-stress conditions.

SILVOLIVE, a Germplasm Collection of Wild Subspecies With High Genetic Variability as a Source of Rootstocks and Resistance Genes for Olive Breeding

“…The diversity of morphological features in olive trees (shoot growth, root development, root-to-shoot biomass ratio, branching habits, total leaf surface, etc.) can be enormously relevant in terms of plant-soil interaction, plant hydraulic properties, water and nutrient uptake abilities, photosynthetic capacity, abiotic stress resistance, etc., as previously shown for a number of SILVOLIVE genotypes (Hernández-Santana et al, 2019). Illustrating the huge phenotypic variability of the collection, genotypes like DHO6A have a root biomass that approximates that of the aerial part ( Supplementary Figure S2), whereas other genotypes like AMK34, AJA7 or CUS14 have a root biomass five times lower than that of their corresponding aerial biomass.…”

“…A higher genetic diversity is still observed in the wild genepool (Lumaret et al, 2004;Baldoni et al, 2009;Belaj et al, 2010;Besnard et al, 2013a;Chiappetta et al, 2017;Kassa et al, 2019). Wild olives therefore represent an important source of genes for crop improvement of resistance to abiotic stresses [e.g., salinity (Cantos et al, 2002), water deficit (Hernández-Santana et al, 2019), soil pollution (Murillo et al, 2005)], vigor (León et al, 2020), crop yield and quality (Hannachi et al, 2008;Baccouri et al, 2011;León et al, 2018), as well as for resistance to biotic factors such as the Verticillium wilt (Colella et al, 2008;Arias-Calderon et al, 2015b;Trapero et al, 2015;Jimenez-Fernandez et al, 2016). Wild olive genotypes have been tested in limited breeding studies, showing potential to shorten the juvenile period or to increase flower production (Klepo et al, 2014), to improve oil composition (Hannachi et al, 2008;León et al, 2018) and to improve resistance to soil-borne diseases (Arias-Calderon et al, 2015a).…”

Study on the Effect of Salt Stress on Yield and Grain Quality Among Different Rice Varieties

“…N concentration in rice flour was determined based on the Kjeldahl method ( Hernandez-Santana et al, 2019 ), and the protein content was derived by multiplying the product of nitrogen content by 5.95 ( Hu et al, 2020 ). The amylose content was determined using iodine colorimetry ( Shaik et al, 2014 ); The gel consistency was determined based on the methods of Cagampang et al (1973) .…”

Current Status of Biodiversity Assessment and Conservation of Wild Olive (Olea europaea L. subsp. europaea var. sylvestris)

“…In this scenario, the availability of wild olive germplasm resources suitable for breeding programs and the preservation of this great source of genetic diversity is crucially important. The potential of wild olive as a source of resistance was widely proved with Verticillium dahliae [18,19] and other biotic and abiotic stresses [20][21][22]. Moreover, the importance of the availability of a large genetic diverse germplasm collection in performing screening aiming to identify resistant genotypes was widely demonstrated [23][24][25][26].…”