Dynamics of low-temperature acclimation in temperate and boreal conifer foliage in a mild winter climate

Abstract

To provide baseline data for physiological studies of extreme low-temperature (LT) tolerance in boreal conifers, we profiled LT stress responses, liquid nitrogen (LN(2))-quench tolerance, and sugar concentrations in foliage of boreal-temperate species pairs in the genera Abies, Picea and Pinus, growing in an arboretum in a temperate oceanic climate from August 2006 through April 2007. The boreal species acclimated more rapidly and deeply than the temperate species, acquiring LN(2)-quench tolerance by late November, despite unusually warm conditions throughout the autumn and early winter. Maximum LT tolerance in the temperate species was in the -25 to -35 degrees C range, and was reached only after a period of freezing temperatures in late January and February. During LT acclimation in the temperate species, sigmoid temperature-relative electrolyte leakage (REL) curves shifted toward lower temperatures, whereas in boreal species there was both a temperature shift and a lowering of the maximum REL until it fell below a threshold associated with irreversible injury. These differences may reflect differences in mechanisms of LT acclimation and LT tolerance. The concentrations of total and individual sugars did not show a clear pattern that could differentiate the boreal and temperate groups. Raffinose and, in three of the six species, stachyose showed the closest association with LT tolerance. Sugar concentrations, principally sucrose, decreased during mild weather, perhaps because of respiratory losses or phloem export, and increased after periods of freezing temperatures. Low-temperature acclimation in boreal species appears to follow a rigid program that may affect their ability to avoid excessive respiratory losses in the event of continued climate warming in boreal regions.

Elevated temperature and CO2 stimulate late season photosynthesis but impair cold hardening in pine

“…4D, inset), but persisted only in the LTAC treatment. In general, Glc and Fru are only observed in minor quantities in conifer needles (Hoch et al, 2003;Strimbeck et al, 2008) because they act as transitory intermediates in Suc synthesis, glycolysis, and regeneration of triose phosphates in the Calvin cycle (Granot et al, 2013). The relatively small but significant increase in Glc and Fru levels in LTAC seedlings clearly suggests an impairment of metabolic activity by low temperature.…”

“…As a consequence, carbon demand in sink tissue decreases toward the end of the growing season, and the bulk of photoassimilate is translocated from source tissues to storage tissues (Hansen and Beck, 1994;Oleksyn et al, 2000). In addition, cryoprotective soluble sugars, including sucrose, raffinose, and pinitol, accumulate in leaf tissues to enhance freezing tolerance (Strimbeck et al, 2008;Angelcheva et al, 2014). Thus, by winter, leaf nonstructural carbohydrates are mainly comprised of mono-and oligosaccharides, and only minimal levels of starch remain (Hansen and Beck, 1994;Strimbeck et al, 2008).…”

“…In addition, cryoprotective soluble sugars, including sucrose, raffinose, and pinitol, accumulate in leaf tissues to enhance freezing tolerance (Strimbeck et al, 2008;Angelcheva et al, 2014). Thus, by winter, leaf nonstructural carbohydrates are mainly comprised of mono-and oligosaccharides, and only minimal levels of starch remain (Hansen and Beck, 1994;Strimbeck et al, 2008). The concurrent decrease of photoassimilate and demand for metabolites that occur during the cessation of growth also impacts the citric acid cycle that mediates between photosynthesis, respiration, and protein synthesis.…”

Cold tolerance in cypress (Cupressus sempervirens L.): a physiological and molecular study

“…As a conclusion, the accessions showing notably reduced photosynthetic efficiency, and particularly clone 52 which showed only 75.45% of the control F v /F m , can be considered more susceptible to freezing damage to PSII after hardening development. Measurement of electrolyte leakage was employed to quantify cold damage to cellular membranes (Hong et al 2009;Strimbeck et al 2008). Broad variation was observed among the cypress plants studied (Fig.…”

“…Correlation between electrolyte leakage and resistance to various abiotic stresses has been established in many plant species. Based on temperature-relative electrolyte leakage curves, Strimbeck et al 2008 showed that boreal species in the coniferous genera Abies, Picea, and Pinus were capable of more rapid and efficient cold acclimation than the corresponding temperate ones. Interspecific hybrids between Pinus strobus and Pinus wallichiana presented differences in freezing-induced electrolyte leakage in different acclimation stages (Lu et al 2007).…”