Abstract Our previous study on bedding plants indicated that blue light in association with low phytochrome activity, relative to red light, can promote elongation growth as one of the shade-avoidance responses. We hypothesized that phototropin is involved in the blue light promotion effects. To test the hypothesis, plant growth and morphology were examined in wild Arabidopsis (Col-0), and its three phototropin-deficient mutants (phot1, phot2, and phot1phot2) under four light quality treatments: (1) R, pure red light (660 nm); (2) B, pure blue light (455 nm); (3) BR, unpure blue light created by mixing B with low-level (6 %) R; and (4) BRF, unpure blue light created by adding low-level far-red light (735 nm) to BR with red/far-red ≈ 1. Continuous (24-h) light-emitting diode lighting with 100 μmol m−2·s−1 photosynthetic photon flux density, and an air temperature of ≈ 23 ℃ were used with the above treatments. The calculated phytochrome photoequilibrium, an indicator of phytochrome activity, was 0.89, 0.69, 0.50, and 0.60 for R, BR, B, and BRF, respectively. After 20 days of light treatments, for the wild-type plants, B or BRF, compared to R or BR, promoted stem elongation, plant flowering, and leaf expansion, showing typical shade-avoidance responses. However, for the phototropin mutants, the promotion effects of B or BRF, relative to R or BR, on the above plant traits were reduced. In the absence of the phototropin(s), plants had reduced stem elongation and delayed flower initiation under B or BRF rather than R or BR, or reduced leaf expansion to a larger degree under B or BRF than R or BR. Our results suggest that phototropin is partly involved in the promotion of stem elongation, plant flowering, and leaf expansion mediated by blue light in association with low phytochrome activity.

中文翻译：

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Phototropin 部分参与蓝光介导的茎伸长、花开始和叶片扩张：野生拟南芥及其 phototropin 突变体之间表型反应的比较

摘要 我们之前对床上用品植物的研究表明，相对于红光，蓝光与低光敏色素活性相关，可以促进伸长生长，作为避荫反应之一。我们假设 phototropin 参与蓝光促进作用。为了验证这一假设，在野生拟南芥 (Col-0) 及其三个缺乏光致素的突变体（phot1、phot2 和 phot1pht2）中在四种光质量处理下检查植物生长和形态：（1）R、纯红光（ 660 纳米）；(2) B、纯蓝光（455nm）；(3) BR，由 B 与低水平 (6 %) R 混合产生的不纯蓝光；(4) BRF，通过向 BR 添加低水平远红光 (735 nm) 产生的不纯蓝光，红色/远红光 ≈ 1。连续（24 小时）发光二极管照明，100 μmol m− 2·s−1 光合光子通量密度，上述处理使用的空气温度约为 23 ℃。对于 R、BR、B 和 BRF，计算出的光敏色素光平衡（光敏色素活性的指标）分别为 0.89、0.69、0.50 和 0.60。经过 20 天的光照处理，对于野生型植物，B 或 BRF 与 R 或 BR 相比，促进茎伸长、植物开花和叶片扩张，表现出典型的避荫反应。然而，对于phototropin 突变体，B 或BRF 相对于R 或BR 对上述植物性状的促进作用降低。在不存在光敏素的情况下，植物在 B 或 BRF 下的茎伸长减少和花的开始延迟而不是 R 或 BR，或者在 B 或 BRF 下比 R 或 BR 减少了更大程度的叶膨胀。我们的结果表明，phototropin 部分参与促进茎伸长，