Abstract：
OBJECTIVE: Long-term exposure over several days to Far-Red (FR) increases leaf expansion, while short-term exposure (minutes) may enhance the PSII operating efficiency (ϕPSII). The interaction between these responses at different time scales, and their impact on photosynthesis at whole-plant level is not well understood. Our study aimed to assess the effects of FR in an irradiance mimicking the spectrum of sunlight (referred to as artificial solar irradiance) both in the long and short-term, on whole-plant CO2 assimilation rates and in leaves at different positions in the plant.
METHODS: Tomato (Solanum lycopersicum) plants were grown under artificial solar irradiance conditions with either a severely reduced or normal fraction of FR(SUN(FR-) vs. SUN). To elucidate the interplay between the growth light treatment and the short-term reduction of FR, we investigated this interaction at both the whole-plant and leaf level. At whole-plant level, CO2 assimilation rates were assessed under artificial solar irradiance with a normal and a reduced fraction of FR. At the leaf level, the effects of removal and presence of FR (0FR and 60FR) during transition from high to low light on CO2 assimilation rates and chlorophyll fluorescence were evaluated in upper and lower leaves.
RESULTS: SUN(FR-) plants had lower leaf area, shorter stems, and darker leaves than SUN plants. While reducing FR during growth did not affect whole-plant photosynthesis under high light intensity, it had a negative impact at low light intensity. Short-term FR removal reduced both plant and leaf CO2 assimilation rates, but only at low light intensity and irrespective of the growth light treatment and leaf position. Interestingly, the kinetics of ϕPSII from high to low light were accelerated by 60FR, with a larger effect in lower leaves of SUN than in SUN(FR-) plants.
CONCLUSIONS: Growing plants with a reduced amount of FR light lowers whole-plant CO2 assimilation rates at low light intensity through reduced leaf area, despite maintaining similar leaf-level CO2 assimilation to leaves grown with a normal amount of FR. The short-term removal of FR brings about significant but marginal reductions in photosynthetic efficiency at the leaf level, regardless of the long-term growth light treatment.
METHODS: Tomato (Solanum lycopersicum) plants were grown under artificial solar irradiance conditions with either a severely reduced or normal fraction of FR(SUN(FR-) vs. SUN). To elucidate the interplay between the growth light treatment and the short-term reduction of FR, we investigated this interaction at both the whole-plant and leaf level. At whole-plant level, CO2 assimilation rates were assessed under artificial solar irradiance with a normal and a reduced fraction of FR. At the leaf level, the effects of removal and presence of FR (0FR and 60FR) during transition from high to low light on CO2 assimilation rates and chlorophyll fluorescence were evaluated in upper and lower leaves.
RESULTS: SUN(FR-) plants had lower leaf area, shorter stems, and darker leaves than SUN plants. While reducing FR during growth did not affect whole-plant photosynthesis under high light intensity, it had a negative impact at low light intensity. Short-term FR removal reduced both plant and leaf CO2 assimilation rates, but only at low light intensity and irrespective of the growth light treatment and leaf position. Interestingly, the kinetics of ϕPSII from high to low light were accelerated by 60FR, with a larger effect in lower leaves of SUN than in SUN(FR-) plants.
CONCLUSIONS: Growing plants with a reduced amount of FR light lowers whole-plant CO2 assimilation rates at low light intensity through reduced leaf area, despite maintaining similar leaf-level CO2 assimilation to leaves grown with a normal amount of FR. The short-term removal of FR brings about significant but marginal reductions in photosynthetic efficiency at the leaf level, regardless of the long-term growth light treatment.
摘要：
目标：长期暴露于远红（FR）几天会增加叶片膨胀，而短期暴露（分钟）可以提高PSII运行效率（φPSII）。这些反应在不同时间尺度上的相互作用，它们对整个植物水平的光合作用的影响尚不清楚。我们的研究旨在评估FR在长期和短期模拟阳光光谱（称为人工太阳辐照度）的辐照度中的影响，全株CO2同化率和植物不同位置的叶片。
方法：番茄（Solanumlycopersicum）植物在人工太阳辐照条件下生长，FR（SUN（FR-）与SUN).为了阐明生长光处理和短期降低FR之间的相互作用，我们在整个植物和叶片水平上研究了这种相互作用。在全厂一级，在正常和降低FR分数的人工太阳辐照度下评估CO2同化率。在叶子层面，在上部和下部叶片中评估了从高光到低光过渡期间FR（0FR和60FR）的去除和存在对CO2同化率和叶绿素荧光的影响。
结果：SUN（FR-）植物的叶面积较低，较短的茎，和比太阳植物更深的叶子。虽然在高光照强度下降低生长过程中的FR不会影响整个植物的光合作用，它在低光照强度下产生了负面影响。短期FR去除降低了植物和叶片的CO2同化率，但仅在低光照强度下，而与生长光处理和叶片位置无关。有趣的是,φPSII从高光到低光的动力学被60FR加速，在太阳的下部叶片中比在太阳（FR-）植物中具有更大的作用。
结论：用减少量的FR光生长的植物通过减少叶面积降低了低光强下的全株CO2同化率，尽管保持与正常量FR生长的叶片相似的叶片水平CO2同化。短期去除FR会导致叶片水平的光合效率显着降低，但略有降低，无论长期生长光治疗。
方法：番茄（Solanumlycopersicum）植物在人工太阳辐照条件下生长，FR（SUN（FR-）与SUN).为了阐明生长光处理和短期降低FR之间的相互作用，我们在整个植物和叶片水平上研究了这种相互作用。在全厂一级，在正常和降低FR分数的人工太阳辐照度下评估CO2同化率。在叶子层面，在上部和下部叶片中评估了从高光到低光过渡期间FR（0FR和60FR）的去除和存在对CO2同化率和叶绿素荧光的影响。
结果：SUN（FR-）植物的叶面积较低，较短的茎，和比太阳植物更深的叶子。虽然在高光照强度下降低生长过程中的FR不会影响整个植物的光合作用，它在低光照强度下产生了负面影响。短期FR去除降低了植物和叶片的CO2同化率，但仅在低光照强度下，而与生长光处理和叶片位置无关。有趣的是,φPSII从高光到低光的动力学被60FR加速，在太阳的下部叶片中比在太阳（FR-）植物中具有更大的作用。
结论：用减少量的FR光生长的植物通过减少叶面积降低了低光强下的全株CO2同化率，尽管保持与正常量FR生长的叶片相似的叶片水平CO2同化。短期去除FR会导致叶片水平的光合效率显着降低，但略有降低，无论长期生长光治疗。
