Nondestructive analysis of photosynthetic pigments in forage radish and vetch

ABSTRACT Chlorophylls and carotenoids are the main photosynthetic pigments in plants, and photosynthetic potential can be used to determine the nitrogen fixation or cycling capacity of cover crops. Therefore, this study quantified and compared the content of photosynthetic pigments in Raphanus sativus and Vicia sativa by using two different methods, namely the extraction method and measurements with a portable chlorophyll meter, and determined whether the results of these two methods showed a significant correlation. Photosynthetic pigments were measured, using both methods, in a greenhouse and laboratory, at four developmental stages: the vegetative stages I (30 days after sowing [DAS]), II (60DAS), and III (90DAS), and the reproductive stage (150DAS). The determination of the photosynthetic pigment content in R. sativus and V. sativa, obtained from the extraction method and chlorophyll index, revealed significant differences depending on the developmental stage in both species. Furthermore, the contents of chlorophyll a, chlorophyll b, and carotenoids determined using the extraction method showed high coefficients of correlation with the total chlorophyll index determined using the portable chlorophyll meter. Therefore, the portable chlorophyll meter can be used for the accurate evaluation of the photosynthetic potential of Raphanus sativus and Vicia sativa, which also saves time and reagents.

摘要 叶绿素（Chlorophylls）与类胡萝卜素（carotenoids）是植物体内主要的光合色素（photosynthetic pigments），光合潜力可用于评估覆盖作物（cover crops）的固氮或养分循环能力。为此，本研究采用两种方法——提取法（extraction method）与便携式叶绿素仪（portable chlorophyll meter）测定法——对萝卜（Raphanus sativus）和箭舌豌豆（Vicia sativa）的光合色素含量进行定量分析与比较，并验证两种方法的测定结果是否存在显著相关性。本研究分别在温室（greenhouse）与实验室（laboratory）环境下，于四个生育期（developmental stages）采用两种方法测定光合色素含量：营养生长期I（播种后30天，DAS）、II（播种后60天，DAS）、III（播种后90天，DAS）以及生殖生长期（reproductive stage，播种后150天，DAS），其中DAS为播种后天数（days after sowing）的英文缩写。对提取法与叶绿素指数法测得的萝卜和箭舌豌豆光合色素含量进行分析后发现，两个物种的光合色素含量均随生育期存在显著差异。此外，提取法测得的叶绿素a（chlorophyll a）、叶绿素b（chlorophyll b）与类胡萝卜素含量，与便携式叶绿素仪测得的总叶绿素指数（total chlorophyll index）均呈现较高的相关系数（coefficients of correlation）。因此，便携式叶绿素仪可用于精准评估萝卜与箭舌豌豆的光合潜力，同时还能节省实验时间与试剂用量。