BACKGROUND & AIMS:
:Chlorophyll fluorescence parameters and spectral reflectance at leaf level were measured at both predawn and noon, under different temperatures and natural light conditions from autumn to winter. Predawn Fv / Fm of both mango (Mangifera indica L.), a tropical fruit tree, and Podocarpus nagi Zoll. et Moritz., a subtropical conifer, decreased with decreasing temperature, with the former to a greater extent than the latter. Yet, predawn Fv / Fm of Taiwan alder (Alnus formosana Makino), a broadleaf tree widely distributed from the lowlands to 3000 m above sea level in Taiwan, was less influenced by temperature. Nevertheless, taking all three species into consideration, predawn Fv / Fm showed a strong correlation with predawn photochemical reflectance index [(PRIp), PRI = (R531 - R570) / (R531 + R570), where R = reflectance]. For the data obtained at noon, ΔF / Fm' showed a significant but weak correlation with PRI (PRIn). However, stronger correlation between ΔF / Fm' and ΔPRI (PRIp - PRIn) was found. In addition, while a non-significant or weak correlation between non-photochemical quenching (NPQ) and PRIn was observed in species sensitive to low temperature, their NPQ was significantly correlated with ΔPRI. We conclude that PRIp can serve as an indicator of the seasonal variation of potential PSII efficiency; and ΔPRI reflects the actual photodissipation as well as actual PSII efficiency during illumination. For the three species in this study, the PRI provides a more consistent measure of the variation in predawn fluorescence values than for steady-state values measured under normal seasonally varying daylight illumination.
背景与目标:
: 在秋季至冬季的不同温度和自然光条件下,在黎明前和中午测量了叶绿素荧光参数和叶片水平的光谱反射率。热带果树芒果 (Mangifera indica L.) 和亚热带针叶树罗汉松 (Podocarpus nagi Zoll. et Moritz。) 的黎明前fv /fm fm随温度降低而降低,前者比后者更大。然而,台湾al木 (Alnus formosana Makino) 的黎明前fv / Fm是一种广泛分布于台湾低地至海拔3000 m的阔叶树,受温度的影响较小。然而,考虑到这三个物种,黎明前fv / Fm与黎明前光化学反射率指数 [(PRIp),PRI = (R531 - R570) / (R531 + R570),其中R = 反射率] 具有很强的相关性。对于中午获得的数据,Δ f / Fm' 与PRI (PRIn) 表现出显着但弱的相关性。然而,发现 Δ f / Fm' 和 Δ pri (PRIp - PRIn) 之间的相关性更强。此外,尽管在对低温敏感的物种中观察到非光化学猝灭 (NPQ) 与PRIn之间的相关性不显着或弱,但它们的NPQ与 Δ pri显着相关。我们得出的结论是,PRIp可以作为潜在PSII效率季节性变化的指标; Δ pri反映了照明过程中的实际光耗散以及实际PSII效率。对于本研究中的三个物种,与在正常季节性变化的日光照明下测得的稳态值相比,PRI提供了对黎明前荧光值变化的更一致的度量。