The effect of water availability on plastic responses and biomass allocation in early growth traits of Pinus radiata D. Don

Abstract

Aim of study: The aim of the study was to assess the effect of water availability on plastic responses and biomass allocation in early growth traits of Pinus radiata D. Don.Area of study: Seedlings of 69 families of P. radiata belonging to five different sites in Central Chile, ranging from coastal range to fothills of the Andes, were grown in controlled conditions to evaluate differences in response to watering.Material and methods: The seedlings were subjected to two watering regimes: well-watered treatment, in which seedlings were watered daily, and water stress treatment in which seedlings were subjected to three cyclic water deficits by watering to container capacity on 12 days cycles each. After twenty-eight weeks root collar diameter, height, shoot dry weight (stem + needles), root dry weight, total dry weight, height/diameter ratio and root/shoot ratio were recorded. Patterns and amounts of phenotypic changes, including changes in biomass allocation, were analyzed.Main results: Families from coastal sites presented high divergence for phenotypic changes, allocating more biomass to shoots, and those families from interior sites presented low phenotypic plasticity, allocating more biomass to roots at the expense of shoots. These changes are interpreted as a plastic response and leads to the conclusion that the local landrace of P. radiata in Chile originating from contrasting environments possess distinct morphological responses to water deficit which in turn leads to phenotypic plasticity.Research highlights: Families belonging to sandy soil sites must be considered for tree breeding in dry areas, selecting those with high root: shoot ratio.Key words: early testing; environmental interaction; ontogeny; plasticity index; water stress.

Changes in drought tolerance of Pinus radiata in Chile associated with provenance and breeding generation

“…During this period, the water supply was withdrawn until the water content of each tray (with 88 containers of 140 cm 3 ) reached ∼30 % of container capacity, determined by weighing a subsample of trays. This watering level was maintained approximately constant until the end of the stress period (Espinoza et al 2013). …”

“…The species was initially established in coastal areas (Albert 1900), but soon after, the process of expansion into other sites (i.e., interior sites) of the country was undertaken. Once established in new environments, radiata pine plantations experienced adaptation to local conditions, which was probably favored by the high plasticity of the species (Zobel and Talbert 1984;Espinoza et al 2013;Mead 2013), resulting in an increased ability to succeed in new environment. According to Schlichting (2004) and Pigliucci et al (2006), differing selection pressure on novel phenotypes could lead to local adaptation.…”

“…Currently, breeding programs are producing the third generation of individuals, and there is no clear intention to include drought tolerance traits within their breeding objectives. Radiata pine can be considered to have a high degree of drought tolerance (Heth and Kramer 1975;Mead 2013) as it has the capability to change its biomass allocation when facing water deficits, allocating more biomass to the roots at the expense of the shoots (Espinoza et al 2013). However, the projected increase in summer drought (CONAMA 2006) creates the necessity of obtaining planting material suitable for drought-prone sites.…”

Effects of induced drought and tilting on biomass allocation, wood properties, compression wood formation and chemical composition of young Pinus radiata genotypes (clones)

“…An average root to shoot (R/S) ratio of 0.60 was observed across all treatments. In most studies focusing on drought stress, the R/S ratio was changed (López et al 2009;Schall et al 2012;Espinoza et al 2013). However, four-year-old Fagus sylvatica L. (European beech) plants (Meier and Leuschner 2008) and Norway spruce plants (Schall et al 2012) subjected to summer drought did not show any changes in R/S ratios.…”

“…Eucalyptus nitens subjected to severe drought had the smallest micro fibrill angle (MFA) and when water stress was released, the MFA began to increase (Wimmer et al 2002). Most studies on the effects of drought on biomass reported changes in biomass allocation pattern between the roots and the shoots (López et al 2009;Schall et al 2012;Espinoza et al 2013). …”