Sakarya University, Faculty of Arts and Sciences, Department of Biology, Esentepe, 54187, Sakarya, Turkey; and Corresponding author. Email:
Hacettepe University, Faculty of Science, Department of Biology, 06800, Beytepe, Ankara, Turkey.
Funct Plant Biol. 2020 Feb;47(3):250-262. doi: 10.1071/FP19200.
In the present study, low temperature-dependent physiological changes were investigated through photosynthetic activity and some endogenous mechanisms in two winter oilseed rape cultivars (Brassica napus L. ssp. oleifera cvv. Eurol and Hansen) on the basis of leaf age. Chlorophyll fluorescence measurements demonstrated that low temperature caused decreased photosynthetic activity in both cultivars. However, photosynthetic apparatus in the young leaves of Hansen is more tolerant to low temperature as demonstrated by lower F0 (minimum fluorescence yield) and 1-qp (excitation pressure of photosystem II), higher Fm (maximum fluorescence yield), Fv/Fm and non-photochemical quenching (NPQ) compared with Eurol. In addition, young leaves of Hansen represented marked increase in some antioxidant enzyme activities (superoxide dismutase (SOD), ascorbate peroxidase (APX) and glutathione reductase (GR)) during cold exposure. In the young leaves of Eurol, however, APX and GR activity was decreased by low temperature, indicating lower efficiency of ascorbate-glutathione cycle. Lower antioxidant activity in the young leaves of Eurol may be responsible for increased malondialdehyde (MDA), H2O2 and membrane damage and decreased chlorophyll content as a result of oxidative damage during cold exposure. In the cold-stressed mature leaves, both cultivars represented similar antioxidant capacities and photosynthetic efficiency. As a consequence, coordinated increase in SOD, APX and GR activities, increased capacity to keep quinone A (QA) in an oxidised state (as indicated by lower 1-qp) and accumulation of soluble sugar and proline could be mainly attributed to higher level of tolerance of the young leaves of Hansen to low temperature when compared with Eurol.
本研究以叶片年龄为基础，研究了两种冬油菜（甘蓝型油菜亚种芸薹种 cvv. Eurol 和 Hansen）低温依赖性生理变化通过光合作用和一些内源性机制。叶绿素荧光测量表明，低温导致两个品种的光合作用活性降低。然而，Hansen 的幼叶中的光合器官对低温更具耐受性，表现为更低的 F0（最小荧光产量）和 1-qp（光系统 II 的激发压力），更高的 Fm（最大荧光产量）、Fv/Fm 和非光化学猝灭（NPQ）比 Eurol。此外，Hansen 的幼叶在冷暴露期间表现出一些抗氧化酶活性（超氧化物歧化酶（SOD）、抗坏血酸过氧化物酶（APX）和谷胱甘肽还原酶（GR））的显著增加。然而，在低温下，Eurol 的幼叶中的 APX 和 GR 活性降低，表明抗坏血酸-谷胱甘肽循环效率较低。Eurol 幼叶中的抗氧化活性较低可能是由于冷暴露期间氧化损伤导致丙二醛（MDA）、H2O2 和膜损伤增加以及叶绿素含量减少的原因。在冷胁迫的成熟叶片中，两个品种表现出相似的抗氧化能力和光合作用效率。因此，SOD、APX 和 GR 活性的协调增加、保持醌 A（QA）处于氧化状态的能力增加（表现为较低的 1-qp）以及可溶性糖和脯氨酸的积累，可以主要归因于 Hansen 幼叶对低温的耐受性高于 Eurol。
