Field‐grown Cotton Exhibits Seasonal Variation in Photosynthetic Heat Tolerance without Exposure to Heat‐stress or Water‐deficit Conditions

Thermotolerance acclimation of photosystem II to heat and drought is well documented, but studies demonstrating developmental impacts on heat tolerance in field‐grown plants are limited. Consequently, climatic variables, estimated canopy temperature, predawn leaf water potential (Ψ_PD), and the temperature responses of maximum quantum yield of photosystem II (F_v/F_m), variable fluorescence (F_v/F₀), quantum yield of electron transport (φ_Eο) and efficiency of PSI electron acceptor reduction (REο/ABS) were characterized for Gossypium hirsutum at three sample times during the growing season (21 June, 2 July and 18 July 2013) under well‐watered conditions. The temperature decreasing a given photosynthetic parameter 15% from the optimum is referred to as T₁₅ and served as a standardized measure of heat tolerance. Ambient and estimated canopy temperatures were well within the optimal range for cotton throughout the sample period, and leaves were verified well watered using Ψ_PD measurements. However, T₁₅ varied with sample date (highest on July 2 for all parameters), being 2 °C (F_v/F₀) to 5.5 °C (φ_Eο) higher on July 2 relative to June 21, despite optimal temperature conditions and predawn leaf water potential on all sample dates. These findings suggest that even under optimum temperature conditions and water availability, heat tolerance could be influenced by plant developmental stage.     

茄子离体叶片光系统Ⅱ的冷激胁迫效应及热力学分析

 以耐冷性较强的短把黑圆茄和耐热性较强的黑帅圆茄为试材,经冷激胁迫后采用植物效率仪PEA,进行快速叶绿素荧光参数测定,并利用最大光化学效率Fv/F m和活性中心RC/CSo的标准状态变性自由能变△GD进行PSⅡ冷稳定性的热力学分析。随着冷激胁迫温度的降低和时间的延长,PSⅡ的Fv/Fm、实际光化学效率ΔF/Fm′、RC/CSo呈"S"型下降趋势;单位反应中心DIo/RC和非光化学猝灭qN呈"S"型上升趋势;综合分析反映出冷激胁迫下PSⅡ反应中心的可逆失活和依赖于叶黄素循环的热耗散的双重机制在保护PSⅡ防止光抑制中起到重要作用。另外,通过两品种间PSⅡ行为差异,引入了两组新的参数作为便于直观比较冷胁迫的评价指标。黑帅圆茄Fv/Fm、ΔF/Fm＇的半衰温度T1/2和t1/2值分别高于短把黑圆茄1.4 ℃和0.8 ℃。茄子叶片Fv/Fm和RC/CSo的△GD随着冷激胁迫温度的降低而减少呈瀑布型的下降趋势。黑帅圆茄的△GD值和变性中点温度Tm都低于短把黑圆茄。它们均反映出黑帅圆茄的耐冷性低于短把黑圆茄。     

开花麻竹叶绿素荧光参数测定

叶绿素荧光是研究光合作用的有效探针。为了探讨开花对麻竹光合作用的影响,应用PAM-100分别测定了开花与未开化麻竹的叶绿素荧光参数。结果表明,随着光强的升高[0~2 000μmol/（m^2·s）],在开始阶段[0~200μmol/（m^2·s）]麻竹叶片的NPQ、Y（NPQ）、Y（ND）、ETR（Ⅱ）和ETR（Ⅰ）均迅速升高,Y（Ⅱ）和Y（Ⅰ）却迅速下降,之后变化缓慢并趋于平稳,而Y（NA）和Y（NO）几乎一直维持平稳;其中未开花麻竹的NPQ、Y（Ⅰ）和ETR（Ⅰ）均高于开花麻竹,Y（Ⅱ）、Fv/Fm和ETR（Ⅱ）无明显差异。在本实验培养光照下[230μmol/（m2·s）],未开花麻竹的NPQ、Y（Ⅰ）和ETR（Ⅰ）也均高于开花麻竹。由此表明,开花引起麻竹PSⅠ的Y（Ⅰ）和ETR（Ⅰ）以及PSⅡ的NPQ降低,这意味着开花麻竹的光保护能力下降,使得PSⅠ受体侧电子积累,导致光合效率下降。     

Physiological Responses of Wheat (Triticum Aestivum L.) –Aegilops Sharonensis Introgression Lines to Excess Copper

Two wheat lines (TL3 and TL5) derived from selection for Cu tolerance among wheat – Aegilops sharonensis hybrids were compared when grown as hydroponics at zero (control), 10⁻⁶ and 10⁻⁵  m CuSO₄. The morphometric measurements showed that the line TL5 with a more inhibited root system under 10⁻⁶  m CuSO₄ had a less inhibited shoot growth under 10⁻⁵  m CuSO₄ as compared to TL3. The decreased maximum efficiency of photosystem II and the more pronounced trend towards increased catalase activity suggested that despite the better shoot growth, the leaves of TL5 were more functionally injured. The increased content of carotenoids at excess Cu and the higher peroxidase and catalase activities of TL3 in control plants might contribute to its better stress tolerance. While no significant changes in enzyme activities were found at 10⁻⁶  m Cu, at 10⁻⁵  m the activities tended to increase. Although the close values of free phenolics concentrations in control plants, at Cu excess their content was higher in TL5 compared to TL3. The free phenolics content in roots at 10⁻⁶  m Cu decreased, and although higher at 10⁻⁵  m Cu, it remained below the control in TL3, and above the control in TL5. From the obtained results TL3 emerged to be more tolerant to excess Cu than TL5.     

Response of hot pepper (Capsicum annuum L.) to mulching practices under planted greenhouse condition

Mulch is considered a desirable management technology for conserving soil moisture, improving soil temperature and soil quality. This study aimed to investigate soil conditions and hot pepper (Capsicum annuum L.) performance in terms of leaf photosynthetic capacity, fruit yield and quality, and irrigation water use efficiency (IWUE) under such practices in greenhouse condition. A field experiment across 3 years was carried out with four types of mulch (without mulch [CK], wheat straw mulch [SM], plastic film mulch [FM], and combined mulch with plastic film and wheat straw [CM]). Mulch could improve soil physical properties regardless of mulch materials. FM and CM treatments improved soil moistures status and soil temperature in comparison to CK control, while SM increased soil water content and decreased soil temperature. Mulch increased leaf net photosynthesis rate (P_N), stomatal conductance to water vapor (gs), intercellular CO₂ concentration (Ci), and transpiration rate (E), but declined instant water use efficiency (WUEi). No significant effect of mulch application on chlorophyll fluorescence was existent for the entire growth season. Fruit yield and irrigation water use efficiency (IWUE) showed some increment under all the mulch conditions. Compared to CK, the yield was enhanced by 82.3%, 65.0%, and 111.5% in 2008; 38.1%, 17.4%, and 46.5% in 2009; and 14.3%, 6.5%, and 19.6% in 2010 under SM, FM, and CM conditions, respectively. Although FM produced better fruit quality than other treatments, CM is the recommended practice for hot pepper cultivation in greenhouse condition due to working well to facilitate soil condition (moisture and temperature), plant growth, and marketable yield.     

普通和控释尿素配合深施提高冬小麦花期旗叶光合性能与氮素利用效率

【目的】探究在不同尿素类型与施用深度下,冬小麦开花后旗叶光合性能和光系统Ⅱ(PSⅡ)性能及氮素利用的差异,以期为协同提高氮素利用效率与籽粒产量,简化小麦生产过程提供理论依据。【方法】于2015—2016年与2016—2017年冬小麦生长季进行试验,以‘济麦22’为供试材料,采用二因素裂区试验设计,尿素类型处理(T)为主区,施用深度处理(D)为裂区。尿素类型包括普通尿素处理(T1,基追比为4∶6)与普通和控释尿素配施处理(T2,普通尿素、硫包膜尿素、树脂包膜尿素以4∶3∶3混合一次性基施),施用深度为地下5 cm (D1)与10 cm (D2)。测定了开花后旗叶气体交换参数和叶绿素荧光诱导动力学曲线(OJIP),及不同生育时期地上植株氮素积累量。【结果】2年试验结果表明,相较于普通尿素处理,普通和控释尿素配施处理可显著提高冬小麦有效穗数和千粒重,对穗粒数影响不显著;施用深度对2016—2017年千粒重影响显著,对2年单位面积有效穗数和穗粒数影响不显著;普通和控释尿素配合深施处理(T2D2)产量显著高于其它处理。尿素类型和施用深度对气体交换参数影响显著,普通和控释尿素配合深施处理可显著提高花后旗叶净光合速率(Pn)和气孔导度(Gs),显著降低胞间CO2浓度(Ci),相对延长了高光合持续期。普通和控释尿素配合处理较普通尿素处理显著提高了旗叶光系统Ⅱ(PSⅡ)反应中心对光能的吸收(φPo)、转化(φEo)以及电子在电子传递链中转移的效率(ψo);显著改善了电子传递链供体侧(Wk)和受体侧(Vj)性能,有效提高了产量形成期光合性能的稳定性。同一尿素类型下,深施处理对光系统Ⅱ(PSⅡ)性能的改善大于浅施处理。相较于普通尿素处理,普通和控释尿素配施处理可显著提高冬小麦生育中后期植株氮素积累量;相较于浅施处理,深施处理对冬小麦不同生育期氮素积累均有不同程度的提高。除对2016—2017年氮素生理利用率(NPE)影响不显著外,普通和控释尿素配合深施处理显著提高了2年冬小麦氮肥农学利用效率(NAE)、氮肥偏肥生产力(PEPN)、成熟期氮肥表观回收率(NRE)和2015—2016年氮素利用效率。【结论】普通尿素与控释尿素配合深施可显著提高冬小麦花期旗叶光合性能,促进氮素利用,增加产量,有利于冬小麦产量与氮肥利用之间的协同提高,省时增效效果明显,是本试验中最佳组合模式。     

钾肥对不同抗虫棉品种叶片光系统Ⅱ性能的影响

【目的】通过对不同抗虫棉品种功能叶叶片PSⅡ性能和有关参数的研究,探讨钾影响棉花叶片光合系统的机理,以期为棉花的钾肥施用提供科学依据。【方法】选用三种抗虫棉岱字棉99B (DP99B)、鲁棉研21(L21)、冀棉169 (J169)为供试材料。设2个施钾水平:施硫酸钾240 kg/hm^2 (K)和不施钾(CK)。于棉花见蕾期,利用便携式LI-6400XT光合仪测定了净光合速率(P_n)、气孔导度(G_s)、胞间CO_2浓度(C_i)。利用M-PEA型植物效率仪快速测定了叶绿素荧光动力学曲线(OJIP曲线)相关参数, PSⅡ反应中心单位活化截面积还原QA的激发能(TR_o/CS_m)、活性反应中心数目(RC/CS_m)、反应中心捕获的激子将电子传递到电子传递链中QA下游的其他电子受体的比例(Ψ_o)以及PSⅡ性能指数(PI_abs),PSⅡ单位反应中心热耗散掉的能量(DI_o/RC)、K点的可变荧光F_k占振幅F_j-F_o的比例(W_k)以及J点的相对可变荧光(V_j)。利用JIP-test进行了叶绿素荧光动力学曲线(OJIP曲线)的参数分析。【结果】施钾对三个棉花品种叶片的P_n、G_s、叶绿素含量、PSⅡ反应中心单位TRo/CS_m、RC/CS_m、Ψ_o以及PI_abs均有显著的提高作用,同时显著降低了PSⅡ的DI_o/RC、K点的W_k以及J点的V_j。施钾后,岱字棉99B (DP99B)、鲁棉研21 (L21)、冀棉169 (J169)的Pn在2016年分别提高了9.60%、19.84%、11.85%,2017年分别提高了9.14%、18.48%、9.60%;PSⅡ的整体性能(PI_abs)分别增加了10.79%、17.93%、14.04%。【结论】施用钾肥有利于提高不同棉花品种叶片PSⅡ反应中心电子供体侧和受体侧以及PSⅡ反应中心电子受体侧之后的电子传递链性能,从而有效提高PSⅡ的整体性能,最终增强了叶片的光合能力。三个品种相比,施钾对L21光合系统的整体改善效果优于DP99B和J169。由此可见,在实际生产中,可以根据不同棉花品种对钾的敏感性合理施钾。但由于我国棉区较多,生产条件差异大,这一结论需在不同的种植区进行进一步验证。     

Monitoring the photosystem II behavior of wild and cultivated barley in response to progressive water stress and rehydration using OJIP chlorophyll a fluorescence transient

To study the effects of progressive drought stress on photosystem II behavior of wild type (Spantaneum) and cultivated barley (Morocco), different levels of soil water availability, including control, moderate, mild, and severe water stress (70%, 50%, 30%, and 10% water holding capacity of soil, respectively) and rehydration were used. Polyphasic OJIP fluorescence transient of Morocco plants exhibited a considerable increase in fluorescence intensity at O, J, and I steps under mild and severe stress relative to slight increase in wild barley. Values of fluorescence parameters and quantum efficiencies, including minimal fluorescence, relative variable fluorescence at phase J and I, maximal quantum yield of photosystem II (PSII), performance index, electron transport yield, and excitation transfer efficiency were influenced by water stress in both genotypes. These parameters were significantly less affected in wild type barley by progressive drought stress compared to Morocco. After re-watering, both genotypes were able to restore from severe drought in most of the traits. Based on our findings, highly correlated values of relative water content (RWC) and independent JIP-test parameters (P < 0.01) indicate that the chlorophyll a fluorescence induction technique is sensitive to plant water status and performance index represent an accurate and reliable indicator for early stress detection and also explore plant vitality under water stress.     

干旱对甜菜叶丛期光系统Ⅱ及光合作用的影响

为探索甜菜(Beta vulgaris)叶丛期叶片光合机构和功能对干旱胁迫的响应机制,以抗旱性相对不同的品种“XJT9907”(旱敏感型)和“XJT9916”(耐旱型)为材料,在甜菜叶丛期控水为45%～50%田间持水量持续7 d时,利用植物效率分析仪(Handy-PEA)测定各处理叶片的叶绿素a荧光诱导动力学曲线(OJIP曲线),同时通过JIP-test数据分析方法,获得有关光系统Ⅱ (PSⅡ)标准化数据、比活性参数、性能指数、总性能指数和能量分配比率。结果表明：1)干旱胁迫增加了XJT9907和XJT9916叶片可变荧光强度,降低叶片电子传递效率(ΨEO, φEO, φRO);2)降低单位面积光能的吸收、捕获、耗散和传递(ABS/CSO, DIO/CSO, ETO/CSO, REO/CSO),其中对耐旱型品种XJT9916的影响较小;3)降低了PSⅡ单元之间的能量连通性和光系统之间的电子传递能力;4) PSⅡ放氧复合体(OEC)失活和PSⅡ受体侧与供体侧电子之间的不平衡;5) XJT9907和XJT9916叶片净光合速率分别降低32.2 %和10.3 %;6) 耐旱型品种XJT9916通过较强的能量耗散(DIO/CSO, DIO/RC)防止了能量被过度激发,致使叶片的净光合速率降低幅度低于旱敏感型XJT9907。XJT9907和XJT9916甜菜叶丛期土壤含水量为45%～50%田间持水量时,叶片光合系统光化学活性降低,电子传递反应和Calvin-Benson循环之间平衡失调,光合机构稳定性和光能利用效率降低,导致叶片光抑制,从而降低了叶片的光合能力。由此可知,干旱胁迫下甜菜光合能力的降低与PSⅡ功能下调有关,与Fv/Fm相比,性能指数PItotal可作为筛选抗旱基因型品种的敏感性指标。