Variability of needle structure in Siberian stone pine in provenance plantations

Abstract

Siberian stone pine (Pinus sibirica Du Tour) is one of the most common trees in Siberia. Its natural range is from the Ural Mountains to the Aldan river and from the Arctic Circle to northern Mongolia. The climate in natural Siberian stone pine sites influences the whole plant organism, particularly its needle structure, and the response to this occurs at specific morphological and anatomical levels. The genotypical and environmental effects on needle structure in different Siberian stone pine ecotypes are very little known. One effective way to examine and to separate genotypical effects from environmental ones is by using a common garden experiment. The purpose is to analyze morphological and anatomical needle variability in Siberian stone pine marginal populations that have been grown in provenance plantations in southern West Siberia, Russia. The needle samples were collected in the provenance plantation located 30 km south of Tomsk (the southeastern West Siberian Plain, southern limit of the taiga zone, optimum site conditions for Siberian stone pine). We investigated the grafts of mother trees taken from natural sites. Four ecotypes were selected for the study. Three ecotypes originated from northern (Urengoy), western (Neviyansk), and eastern (Severobaikalsk) marginal populations. The fourth, the Tomsk ecotype, was a local control. The local Tomsk ecotype grows on a site where natural conditions are worse due to reduction of mean annual temperature and increase of the humid factor northward, humidity reduction eastward and its rise westward. Variability of 10 needle morphological and anatomical characteristics was studied. The northern ecotype had smaller needle length (28%), leaf cross-section area (21%), mesophyll area (29%), mesophyll cell size (27%), and conducting bundle area (16%) but the number of stomata per unit leaf area increased by 16% over the local Tomsk ecotype. The resin canal area, epidermal and hypodermal cell thickness, and stomata size were equal to both the northern and local ecotypes. The leaf cross-section and mesophyll area in the western ecotypes decreased by 20% and 23%, respectively, but stomata size increased by 12%. The needle length, mesophyll cell size, conducting bundle area, resin canal area, the number of stomata per unit leaf area, and epidermal and hypodermal cell thickness did not differ significantly from the same characteristics in the Tomsk ecotype. The leaf cross-section area, mesophyll area, and mesophyll cell size in the eastern ecotype decreased by 22%, 37% and 20% respectively, as compared with the local ecotype. All other studied needle characteristics did not differ from the local ecotype. The common morphological and anatomical parameters did not change from south to north and from west to east (resin canal area and hypodermal cell thickness) and parameters varied in each ecotype. For example, needle length, conducting bundle area, and the number of stomata per unit leaf area changed along latitude but did not change along longitude. Conversely, stomata size and epidermal cell thickness changed along longitude but did not change along latitude. Thus the morphological and anatomical characteristics were specific for each ecotype. The parameter variability of the needle structure is hypothesized to relate to graft geographical provenance that depends on genotype and adaptation properties of mother trees.