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

<p><em>Aim of study: </em>The aim of the study was to assess the effect of water availability on plastic responses and biomass allocation in early growth traits of <em>Pinus radiata </em>D. Don.</p><p><em>Area of study: </em>Seedlings of 69 families of <em>P. radiata </em>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.</p><p><em>Material and methods: </em>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.</p><p><em>Main results: </em>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 <em>P</em>. <em>radiata </em>in Chile originating from contrasting environments possess distinct morphological responses to water deficit which in turn leads to phenotypic plasticity.</p><p><em>Research highlights: </em>Families belonging to sandy soil sites must be considered for tree breeding in dry areas, selecting those with high root: shoot ratio.</p><p><strong>Key words</strong>: early testing; environmental interaction; ontogeny; plasticity index; water stress.