The effect of photoperiod and thermoperiod on cold acclimation and growth of <i>Pinus</i><i>sylvestris</i>

Low temperature acclimation and growth of roots and shoots of Scots pine seedlings (Pinussylvestris L.) under long day or short day (SD), and warm temperature or low temperature (LT) treatments were compared. Three methods were used to evaluate shoot injury; measurement of electrolyte leakage, regrowth, and visual microscopic evaluation were also compared to determine their usefulness in root injury evaluation. Visual evaluation was the most accurate and convenient technique for assessing LT root injury. Under all treatments shoots were hardier than roots with maximum hardiness of −40 and −15 °C, respectively, induced by SD/LT treatment. Stems acclimated and ceased growth in response to SD and LT, while only LT induced root acclimation and growth cessation. SD treatment does not induce substantial root cold acclimation and it reduces root growth primarily by limiting the availability of assimilates. White root tips were acclimated to −10 °C and did not affect the cold hardiness of more mature portions of the root. </jats:p

Scots pine fine roots adjust along a 2000-km latitudinal climatic gradient

Patterns of plant biomass allocation and functional adjustments along climatic gradients are poorly understood, particularly belowground. Generally, low temperatures suppress nutrient release and uptake, and forests under such conditions have a greater proportion of their biomass in roots. However, it is not clear whether ‘more roots’ means better capacity to acquire soil resources. Herein we quantified patterns of fine-root anatomy and their biomass distribution across Scots pine (Pinus sylvestris) populations both along a 2000-km latitudinal gradient and within a common garden experiment with a similar range of populations. We found that with decreasing mean temperature, a greater percentage of Scots pine root biomass was allocated to roots with higher potential absorptive capacity. Similar results were seen in the common experimental site, where cold-adapted populations produced roots with greater absorptive capacity than populations originating from warmer climates. These results demonstrate that plants growing in or originated from colder climates have more acquisitive roots, a trait that is likely adaptive in the face of the low resource availability typical of cold soils