海盐对绿竹叶片反射光谱及叶绿素荧光参数的影响

Abstract

沿海防护林是海岸生态系统中最基本的生物资源，由于沿海地区地下水位高，土壤含盐量高，肥力低，生态环境恶劣等特点，所以优良植物种选择是加快沿海优良防护林体系建设的关键。为了探讨绿竹耐盐性以及为沿海地区防护林选择优良植物种，以2 年生绿竹 （<em>Bambusa oldhamii</em>） 为材料，采用水培法进行不同浓度的海盐处理，利用 Unispec-SC 型单通道光纤光谱仪和非调制式叶绿素荧光仪对绿竹叶片反射光谱和叶绿素荧光参数等进行测定。结果表明：当海盐浓度小于1.2%时，绿竹叶片中叶绿素a、叶绿素b和类胡萝卜素含量，以及"三边"参数与对照无显著差异，当海盐浓度升高到1.6%时，色素与对照相比分别降低了63.2%、62.8%和47.2% （<em>P</em> < 0.01），红边位置 （<em>λ</em>_red） 和红边面积 （<em>S</em>_red） 相比对照显著减小 （<em>P</em> < 0.05）。1.2%浓度的海盐处理，红边归一化指数 （<em>rNDVI</em>）、绿度归一化指数 （<em>gNDVI</em>）、类胡萝卜素反射指数2 （<em>CRI</em>₇₀₀） 和光化学反射指数 （<em>PRI</em>） 显著降低 （<em>P</em> < 0.05），与对照相比分别降低了27.3%、23.3%、19.5%和43.9%；当海盐浓度增加到1.6%时，<em>rNDVI</em> 、改良红边比值指数 （<em>mND</em>）、<em>gNDVI</em> 、改良归一化差值指数 （<em>mSR</em>₇₀₀）、类胡萝卜素反射指数1 （<em>CRI</em>₅₅₀）、<em>CRI</em>₇₀₀和<em>PRI</em> 等参数与对照相比分别下降了42.4%、43.9%、32.6%、21.5%、47.2%、49.9%和58.5%。绿竹叶片PSⅡ最大量子产率 （<em>F</em>_v/<em>F</em>_m）、电子传递的量子产额 （<em>ΦE</em><em>_o</em>）、单位反应中心捕获的用于电子传递的能量 （<em>ET</em>_<em>o</em>/<em>RC</em>）、单位面积反应中心数目 （<em>RC/CS</em>） 和叶片性能指数 （<em>PI</em>_ABS） 等参数，1.6%海盐处理与对照相比分别降低了50.8%、28.6%、21.7%、52.1%和92.3%，单位反应中心复合体吸收的能量 （<em>ABS/RC</em>） 比对照提高了96.9%。说明绿竹具有一定的耐盐性。;The coastal protection forest is the most basic living resources in the coastal ecosystem. Due to the high underground water level, high soil salt content, low fertility, and deteriorated ecological environment in the coastal area, the selection of plant species is the key to speed up the construction of coastal protection forest system. To evaluate the salt tolerance of <em>Bambusa oldhamii</em> and provide plant species for coastal protection forest in the coastal area, we investigated reflectance spectra and chlorophyll fluorescence parameters in the leaves of 2 years <em>B. oldhamii</em> under sea salt stress by hydroponics using Unispec-SC spectrometer and non-modulated chlorophyll fluorometer, respectively. Results showed that when the sea salt concentration was under 1.2%, the contents of chlorophyll a, chlorophyll b and carotenoids, and reflectance spectra parameters were not significantly different with that under control. However, when the sea salt concentration was 1.6%, the contents of chlorophyll a, chlorophyll b and carotenoids were decreased by 63.2%, 62.8%, and 47.2% (<em>P</em> < 0.01), respectively and reflectance spectra parameters red wavelength (<em>λ</em>_red) and red area (<em>S</em>_red) were significantly reduced (<em>P</em> < 0.05) compared with control. The red-edge normalized difference vegetation index (<em>rNDVI</em>), greenness normalized index (<em>gNDVI</em>), carotenoids reflectance indexes Ⅱ (<em>CRI</em>₇₀₀) and photochemical reflectance index (<em>PRI</em>) under 1.2% sea salt concentration was reduced by 27.3%、23.3%、19.5% and 43.9%, respectively compared with control. The <em>rNDVI</em>, modified red-edge normalized difference vegetation index (<em>mND</em>), <em>gNDVI</em>, modified red-edge ratio (<em>mSR</em>₇₀₀), carotenoids reflectance indexesⅠ (<em>CRI</em>₅₅₀),<em>CRI</em>₇₀₀ and <em>PRI</em> under 1.6% sea salt concentration was reduced by 42.4%, 43.9%, 32.6%, 21.5%, 47.2%, 49.9% and 58.5%, respectively compared with control. The maximum quantum yield of photosystemⅡ (<em>F</em>_v<em>/F</em>_m), quantum yield for electron transport (<em>ΦE</em>_o), electron transport flux per reaction center (<em>ET</em>_o<em>/RC</em>), density of reaction center (QA-reducing PSⅡ reaction centers) (<em>RC/CS</em>) and performance index on absorption basis (<em>PI</em>_ABS) under 1.6% sea salt concentration was reduced by 50.8%, 28.6%, 21.7%, 52.1%, and 92.3% respectively while the absorption flux per reaction center (<em>ABS/RC</em>) increased 96.9% compared with control. The above results showed that high salt stress inhibited the synthesis of the chlorophyll, reduced the absorption of the light energy, resulted in light inhibition and the damage of the acceptor side from PSⅡ, reaction center degradation or inactivation, and inhibited directly growth and development of bamboo. While under low salt stress, the salt tolerance of bamboo was improved by increasing chlorophyll content, light absorption, <em>F</em>_v/<em>F</em>_m, <em>ΦE</em>_o, <em>ET</em>_o/<em>RC</em>, <em>RC</em>/<em>CS</em> and <em>PI</em>_ABS.