苗期低温胁迫对“红颜”草莓叶绿素含量及冠层高光谱的影响

Effects of Low Temperature Stress at Seedling Stage on Chlorophyll Content and Canopy Hyperspectral of"Hongyan"Strawberry

2020年9月-2021年1月以"红颜"(Fragaria×ananassa Duch"Benihope")草莓为试材,在南京信息工程大学开展低温环境控制试验。设置21℃(日最高气温)/11℃(日最低气温)、18℃/8℃、15℃/5℃和12℃/2℃共4个低温处理,持续时间设置3d、6d、9d、12d共4个水平,以25℃/15℃为对照(CK)。测定草莓叶片叶绿素含量以及冠层高光谱反射率,研究低温胁迫对草莓叶绿素含量及冠层反射光谱的影响,筛选出叶绿素含量估算模型的敏感波段与特征参数。结果表明:(1)同一低温条件下,草莓叶片叶绿素a、叶绿素b和总叶绿素(a+b)等参数随着胁迫天数的延长而减少;同一胁迫天数下,温度越低其含量越低,即低温胁迫程度越大叶绿素含量下降幅度也越大。(2)不同温度同一胁迫天数处理草莓苗期冠层光谱反射率变化规律大致相同。在可见光区域草莓冠层反射光谱曲线均存在绿峰和红谷,在近红外反射平台随着温度降低,光谱反射率数值逐渐增大,即反射平台逐渐增高。(3)草莓冠层一阶微分光谱曲线变化较剧烈,有明显波峰和波谷,在红边范围内偶有双峰现象。随着低温胁迫程度的加深,一阶微分光谱最高峰的值越高,草莓冠层光谱的近红外反射率升高,红边位置蓝移,之后该峰值逐渐降低,红边位置红移。(4)草莓叶绿素(a+b)含量与冠层原始光谱反射率的相关系数均呈负相关,与原始光谱的近红外波段反射率的相关性明显高于可见光波段。叶绿素(a+b)含量与原始光谱反射率相关性较好,均达到显著水平,其中737nm波段相关系数达到最大,因此可以用其作为敏感波段对叶绿素含量进行预测。叶绿素(a+b)含量与植被指数中的DVI、MSAVI、PVI、RDVI、SAVI和TSAVI的相关性达极显著水平,可以选其作为特征参数对叶绿素含量进行预测。

From September 2020 to January 2021,take"hongyan"(Fragaria×ananassa Duch"Benihope")strawberry as test material to carry out low temperature environmental control test in Nanjing University of Information Science and Technology.Four low temperature treatments 21℃(daily maximum temperature)/11℃(daily minimum temperature),18℃/8℃,15℃/5℃and 12℃/2℃were set,and the duration was set at four levels of 3 d,6 d,9 d and 12 d,with 25℃/15℃as the control(CK).The chlorophyll content of strawberry leaves and canopy hyperspectral reflectance were measured.The effects of low temperature stress on chlorophyll content and canopy reflectance spectrum of strawberry were studied.The sensitive bands and characteristic parameters of chlorophyll content estimation model were selected.The results show that:(1)Under the same low temperature condition,Chla,Chlb and Chl(a+b)content of strawberry leaves decreased with the extension of stress days.Under the same stress days,the lower the temperature,the lower Chla,Chlb and Chl(a+b)content,that is,the greater the degree of low temperature stress,the greater the decline of chlorophyll content.(2)The changes of canopy spectral reflectance of strawberry seedlings under different temperatures and the same stress days were roughly the same.In the visible region,there are green peaks and red valleys in the reflection spectrum curve of strawberry canopy.In the near-infrared reflection platform,the spectral reflectance increases gradually with the decrease of temperature,that is,the reflection platform increases gradually.(3)The first-order differential spectrum curve of strawberry canopy changed violently,with obvious peaks and valleys,and occasionally double peaks in the red edge range.With the deepening of low temperature stress,the higher the value of the highest peak of the first-order differential spectrum,the near-infrared reflectance of strawberry canopy spectrum increased and the red edge position shifted blue,and then the peak gradually decreased and the red edge position shifted red.(4)The correlation coefficient between Chl(a+b)content and original spectral reflectance of strawberry canopy is negatively correlated.The correlation between Chl(a+b)content and reflectance in near-infrared band is significantly higher than that in visible band.The correlation between Chl(a+b)content and original spectral reflectance is good,reaching a significant level.The correlation coefficient of 737 nm band is the largest,so it can be used as a sensitive band to predict chlorophyll content.The correlation between Chl(a+b)content and DVI,MSAVI,PVI,RDVI,SAVI and TSAVI in vegetation index is very significant,which can be selected as a characteristic parameter to predict chlorophyll content.