秸秆还田对长期连作棉花光合速率及叶绿素荧光的影响

利用棉花长期连作定点微区试验,通过比较秸秆还田和非秸秆还田条件下长期连作对棉花光合作用及叶绿素荧光参数的影响。结果表明:随着连作年限增加,棉花叶片叶绿素相对含量和光合速率呈下降趋势,特别是连作20年后光合速率下降明显,秸秆还田后连作5、10和15年分别比非秸秆还田增加了11.9%、1.8%和3.6%,说明连作障碍在短期内表现明显,秸秆还田能在一定程度上缓解棉花连作障碍,但在20年以后连作障碍持续影响棉花的生长。棉花连作5～10年PSII原初光能转换效和PSII潜在活性均表现出先下降后上升的趋势,光合活性受到暂时抑制,光合器官并未受到损伤,说明棉花连作主要是通过降低叶片PSII原初光能转换效率和光化学荧光猝灭系数,引起单叶光合速率下降,最终影响棉花植株生理生长。

不同方位栽植的鹅掌藤生理生态特性研究

垂直绿化通过对空间的充分利用增加了绿化面积,对城市生态恢复与环境美化意义深远。受到太阳活动的影响,不同方位的垂直绿化所处微环境存在一定差异,其生理生态特性也会随之发生响应。以鹅掌藤(Schefflera arboricola)为研究对象,测定其在室外不同方位(建筑墙面朝向)的生长、光合和荧光生理、叶片养分含量等生理指标的差异。结果发现,北向鹅掌藤的比叶重较低,其净光合速率(10.52μmol/m^2·s)、气孔导度(0.22 mol/m^2·s)、蒸腾速率(4.31 mmol/m^2·s)、非光化学淬灭(0.72)最高;南向鹅掌藤的叶绿素SPAD值(59.33)、叶绿素荧光指标值、比叶重(140.16 g/m^2)及镁含量(3.86 g/kg)和硫含量(4.98 g/kg)含量较高,但氮含量(16.57 g/kg)、磷含量(0.95 g/kg)、钙含量(15.15 g/kg)含量较低,净光合速率相对适中;西向鹅掌藤受到气孔限制影响,其净光合速率(6.08μmol/m^2·s)最低。结果表明在垂直绿化中鹅掌藤最适宜生长在北向的墙面上,南向次之,西向较差。

Effects of NaCl Stress on Chlorophyll Fluorescence Parameters in Cinnamomum japonicum var. chenii

[ Objective ] Study on the changes of chlorophyll fluorescence parameters in Cinnamomumjaponicum var. chenii under NaCl stress. [ Method ] The seedling growth increment, chlorophyll content and chlorophyll fluorescence parameters in leaves of 1-year old Cinnamomum japonicum var. chenii were investigated in field experiment. [ Result] Under NaC1 stress, seedling growth increment reduced and the chlorophyll content decreased to a stable value ; changes of Fv/Fm and Fv/Fo showed identical increasing trend and double peak type. With the aggravation of salt stress, most variations were observed in Fo, correlations among chlorophyll fluorescence parameters presented ＂rise-drop＂ trend （in.the treatment of 7 g/L NaCl）. [ Conclusion] Cirmamomum japonicum vat. chenii is endowed with strong salt resistance and wide adaptability.

Chlorophyll-a Fluorescence in Ecology： Theoretical Considerations and Examples around Marine Macroalgae

Over the last decades, the usage of PAM （pulse amplitude modulated） fluorometers for assessment of chlorophyll-a fluorescence variations became widely applied on marine macroalgae physiology and ecophysiology researches. Due to the increased use of these methods, a large number of studies, mainly relating to macroalgae ecology and physiology were worldwide reported. In this context, it was also created a mismatch of concepts about fluorescence of the chlorophyll-a and its application. Under this background, this study compile and summarize the state of the art knowledge regarding to the chlorophyll fluorescence, contextualizing the use of the PAM method with the main factors regulating photosynthesis （light, temperature, salinity nitrogen and phosphorus） in marine macroalgae. Moreover, this study also references the most used terms and shows some examples found in literature about the applicability of fluorescence parameters. The herein findings and the discussed examples, helps to emphasize the importance of fluorescence usage, that highlights the understanding of photosynthetic responses in macroalgal physiology and ecology.

Use of Chlorophyll Fluorescence Methods for the Study of Physiological Condition and Resistance against Abiotic Factors of Grapevine

The purpose of this study was to explore influence of abiotic factors, such as high temperature, water deficiency and high solar radiation on the photomembrane of grapevine leaves. Grapevine leaves were collected from variety Rkatsiteli （Vitis vinifera） and placed at a temperature of ＋45 ℃ and ＋55 ℃ for 5 rain, respectively. The relative volume of water in leaves was gradually reduced to 50%, and then leaves were irradiated with 6,000 pmol/m2.s of white light. Changes provoked by stressful abiotie factors were determined using rapid and delayed chlorophyll fluorescence methods. It was shown that value of variable component of chlorophyll fluorescence （Fv）, intensity of electron transport between the photosystems （ETR）, intensity of expended electrons in carboxylation （ETRn） and oxygenation （ETRp） and index of non-photochemical quenching （NPQ）, allow studying molecular mechanisms of the impact of abiotic factors and the resulting damage degree. Based on delayed and rapid fluorescence data, it was demonstrated that temperature of ＋45 ℃ adversely affects oxygen production system and CO2 assimilation mechanisms, while at ＋55 ℃, the ETR decreases. Reduction of relative water volume in leaves up to 50%-55% leads to sharp reduction in ETR and inhibition of photosynthesis. In case of irradiation of leaves with high-intensity light of 6,000 μmol/m2.s, NPQ of light falling on a leaf increases, thus protecting photosynthesis apparatus from damage.