Forest Resources Unit, Research and Technology Agricultural Centre (CITA), Government of Aragon, Zaragoza, Spain.
PLoS One. 2011;6(12):e28772. doi: 10.1371/journal.pone.0028772. Epub 2011 Dec 29.
As part of a program to select maritime pine (Pinus pinaster Ait.) genotypes for resistance to low winter temperatures, we examined variation in photosystem II activity by chlorophyll fluorescence. Populations and families within populations from contrasting climates were tested during two consecutive winters through two progeny trials, one located at a continental and xeric site and one at a mesic site with Atlantic influence. We also obtained the LT₅₀, or the temperature that causes 50% damage, by controlled freezing and the subsequent analysis of chlorophyll fluorescence in needles and stems that were collected from populations at the continental trial site.P. pinaster showed sensitivity to winter stress at the continental site, during the colder winter. The combination of low temperatures, high solar irradiation and low precipitation caused sustained decreases in maximal photochemical efficiency (F(v)/F(m)), quantum yield of non-cyclic electron transport (Φ(PSII)) and photochemical quenching (qP). The variation in photochemical parameters was larger among families than among populations, and population differences appeared only under the harshest conditions at the continental site. As expected, the environmental effects (winter and site) on the photochemical parameters were much larger than the genotypic effects (population or family). LT₅₀ was closely related to the minimum winter temperatures of the population's range. The dark-adapted F(v)/F(m) ratio discriminated clearly between interior and coastal populations.In conclusion, variations in F(v)/F(m), Φ(PSII), qP and non-photochemical quenching (NPQ) in response to winter stress were primarily due to the differences between the winter conditions and the sites and secondarily due to the differences among families and their interactions with the environment. Populations from continental climates showed higher frost tolerance (LT₅₀) than coastal populations that typically experience mild winters. Therefore, LT₅₀, as estimated by F(v)/F(m), is a reliable indicator of frost tolerance among P. pinaster populations.
作为选择抗低温冬季的海洋松（Pinus pinaster Ait.）基因型的计划的一部分，我们通过叶绿素荧光检查了光系统 II 活性的变化。在两个连续的冬季，通过两个后代试验，在大陆性和干旱地区的种群和种群内，以及在具有大西洋影响的湿润地区的种群内进行了试验。我们还通过受控冻结获得了 LT₅₀（导致 50%损伤的温度），并随后分析了来自大陆试验点的种群收集的针叶和茎中的叶绿素荧光。海洋松在寒冷的冬季对大陆站点的冬季胁迫敏感。低温、高太阳辐射和低降水的结合导致最大光化学效率（F(v)/F(m)）、非循环电子传递的量子产量（Φ(PSII)）和光化学猝灭（qP）持续降低。光化学参数的变化在家族之间大于种群之间，并且仅在大陆站点最恶劣的条件下才出现种群差异。正如预期的那样，环境效应（冬季和地点）对光化学参数的影响远大于基因型效应（种群或家族）。LT₅₀与种群范围的最低冬季温度密切相关。暗适应的 F(v)/F(m) 比值清楚地区分了内陆和沿海种群。总之，对冬季胁迫的 F(v)/F(m)、Φ(PSII)、qP 和非光化学猝灭（NPQ）的变化主要是由于冬季条件和地点之间的差异，其次是由于家族之间的差异及其与环境的相互作用。来自大陆性气候的种群显示出较高的抗霜性（LT₅₀），而沿海种群通常经历温和的冬季。因此，通过 F(v)/F(m) 估计的 LT₅₀是海洋松种群抗霜性的可靠指标。
