Effect of Defoliants Application on Physiological Characters of Cotton Leaf without Defoliants

[Objective]The aim of this study is to elucidate the physiological mechanism of cotton leaf without defoliant response to thidiazuron (TDZ). [Method] A pot experiment was conducted to study the effect of defoliants on the photosynthesis, chlorophyll fluorescence, antioxidant enzyme activity, and endogenous hormone contents of cotton leaf without defoliant at 1 d, 3 d, 6 d and 10 d after the application of TDZ. Cultivar CCRI-50 was used for this experiment. [Result] TDZ rapidly induced cotton leaf abscission, however, no abscission was detected to the cotton leaf without defoliants. The net photosynthetic rate (P_n) of cotton leaf without defoliants was reduced by 1 d, 3 d and 6 d after TDZ applied, but rise to the control treated with water level by 10 d. TDZ also caused a significant decline in the maximum photochemical efficiency of photosystem II (F_v/F_m), the quantum yield of electron transport (Φ_PSII), the electron transport rate (R_et) and the photochemical quenching coefficient (q_P), but an increase in the non-photochemical quenching coefficient (qNP). However, with the same changes as P_n, the chlorophyll fluorescence characters got to the control by 10 d. TDZ application significantly increased the superoxide dismutase activity, did not affect the peroxidase activity, decease the malondialdehyde content. Abscisic acid contents in the cotton leaf without defoliant were lower than control by 3 d and 6 d after the applied of TDZ, but have the same level with control at 10 d, and the auxin had a little changes compared with control during the whole period of experimental time. [Conclusion] TDZ application significantly affect the photosynthesis, chlorophyll fluorescence, antioxidant enzyme activity, and endogenous hormone contents of cotton leaf without defoliant. When the leaf with defoliant drop off, the physiological characters of cotton leaf without of defoliants recovered to control level, and no abscission were detected.     

Chemical Defoliation of Machine-Harvested Cotton was Accompanied by Intense Ethylene and Cytokinin Signal Responses

[Objective] Chemical defoliation is a necessary technical measure for machine-harvested cotton, and the effect of chemical defoliation directly affects the efficiency of mechanical-picking and fiber quality. Study on the molecular mechanism of defoliant in regulating defoliation could effectively guide the screening and improvement of defoliant-sensitive cotton germplasms. [Method] In this study, 200 cotton accessions were collected and planted in greenhouse, and treated with defoliant at the early flowering stage. Different varieties with high or low sensitivity to defoliant were selected according to the defoliation rate on the 4th day after treatment. The selected cotton varieties were also treated with defoliant at the boll opening stage in the field, and the defoliation rate on the 7th day after treatment was calculated. Meanwhile, samples from the abscission zone of the selected varieties were collected on the first and third day after treatment. And the expression of ethylene-, cytokinin- and hydrolase- related genes were analyzed by quantitative real-time polymerase chain reaction (qRT-PCR). [Result] Six defoliant sensitive and 6 insensitive varieties were selected from greenhouse and field tests. According to the qRT-PCR results, cytokinin-related genes, ethylene-related genes and hydrolase-related genes showed different expression patterns following defoliant treatment in different varieties, and most of these genes showed significant different expression in the defoliant sensitive and insensitive varieties. [Conclusion] This study indicates that different cotton germplasms respond to differently to defoliant, which might be the result of differential expression of cytokinin- and ethylene-related genes.     

新疆机采棉花实现叶片快速脱落需要的温度条件

随着机采棉的快速推进,籽棉含杂率过高导致清理工序过多及纤维不必要的损伤。新疆棉区棉花生长后期的热量资源有限,如何合理喷施脱叶催熟剂是改善原棉品质的关键技术措施。本研究采用分期喷施脱叶催熟剂的方式,探讨了温度变化对棉花叶片脱落率的影响及实现棉花叶片快速脱落需要的温度条件。结果表明,在喷施脱叶催熟剂后(7.0±1.0)d内,棉花叶片脱落率最高,达55%～79%,且与最高温度和每日≥12°C有效积温呈显著的线性关系。若要在喷施脱叶催熟剂后(7.0±1.0)d内实现>55%的叶片脱落率,则应满足该时间段最高温度大于27.2°C、每日≥12°C有效积温大于7.0°C·日的要求。因此,喷施脱叶催熟剂后(7.0±1.0) d内是实现良好脱叶效果的关键时间段,期间的最高温度和每日≥12°C有效积温则是影响的关键因素。     

脱叶剂对棉花叶片叶绿素荧光动力学参数的影响

利用叶绿素荧光动力学测定技术,对脱叶剂的不同喷施时间条件下棉花叶片光能吸收、传递、转换特性及棉花产量进行了研究。结果表明喷施脱叶剂降低了棉花叶片的光合功能,降低了最大光化学效率(Maximum photochemical efficiency,Fv/Fm)及PSⅡ反应中心开放部分的比例,使初始荧光(Minimal fluorescence,Fo)上升、光合电子传递速率(Electron transport rate,ETR)和PSⅡ总的光化学量子产量(Photosynthetic quantum yield,Yield)降低,提高了非光化学猝灭系数(Non-radiant energy,NPQ),说明脱叶剂胁迫下棉花叶片发生了光抑制,PSⅡ复合体受到损伤伴随着光合电子传递受阻。吐絮率10%时喷施脱叶剂使棉花铃重、衣分、皮棉产量显著低于对照。吐絮率50%时喷施脱吐隆300 g·hm~(-2)+40%乙烯利1200 m L·hm~(-2),第25天棉花脱叶率为90.1%,吐絮率为99.87%,对棉花铃重、衣分及皮棉产量影响最小且更有利于促进叶片脱落和棉铃成熟。     

水稻叶氮量等生理参数的叶位分布特点及其与氮素营养诊断的关系

以氮素营养特性差异较大的3个品种为材料,研究了水稻不同生育期顶部4片展开叶中叶片总氮、叶绿素和游离氨基酸及叶鞘总氮含量的叶位分布特点。各生育期叶片和叶鞘总氮含量均以顶1叶最高,而游离氨基酸和叶绿素的最高含量叶位随品种和生育期而异。抽穗前游离氨基酸的最高含量叶位随品种和生育期变化较大,而抽穗后以顶1叶含量     

叶菜型甘薯品种‘百薯1号’茎尖不同部位淀粉含量变化的研究

研究了叶菜型甘薯品种茎尖的淀粉含量,为叶菜型甘薯品种茎尖的合理利用提供理论依据。以叶菜型甘薯品种‘百薯1号’为材料,研究分析了不同采摘时期甘薯茎尖不同部位淀粉含量的变化规律。结果表明：甘薯茎尖中叶、茎、柄的淀粉含量在不同采摘时期间均存在极显著差异。不同部位的平均淀粉含量从大到小排序依次是茎>叶>柄。其变异系数由大到小排序依次是叶>茎>柄。叶的淀粉含量以采摘第1期的最大,第2期的最低。在第1期至第4期范围内,叶的淀粉含量呈高→低→高→低的变化趋势;在第4期以后,则呈逐渐升高趋势。茎的淀粉含量以第7期的最高,第3期的最低。在采摘第1期至第3期以及第4期至第6期范围内,茎的淀粉含量均呈下降趋势。柄的淀粉含量以第6期的最高,第3期的最低。在第1期至第3期范围内,柄的淀粉含量呈缓慢下降趋势;第3期以后直至第6期范围内,柄的淀粉含量呈缓慢上升趋势;第6期至第7期,柄的淀粉含量又呈迅速下降趋势。叶、茎、柄三部位间淀粉含量变化存在着复杂的关系,但呈现出部分明显的关联规律。     

库大小对水稻不同叶位叶片氮代谢的影响

采用去穗与疏花方式调节库大小，研究了对水稻不同叶位叶片氮代谢的影响。去穗或疏花后，已完成发育的源叶片，尤其是顶4叶，蛋白质合成重新旺盛，蛋白氮含量提高，出现了类似于生长库的氮代谢特征。水稻叶片的酸性转化酶活力可反映其蛋白质合成能力，据此可判断叶片是属于氮素供应源还是氮素接受库。研究证实下位叶的氮代谢     

棉花主茎叶与根系硝酸还原酶活性分布对播期和密度的响应

【目的】本研究旨在探讨大田轻简化栽培条件下棉花氮代谢随播期和密度的变化规律。【方法】选用华棉3109(G.hirsutum L.)于2014年在华中农业大学试验农场,采用裂区设计:播期为主区(S1,5月30日;S2,6月14日),密度为副区(D1,7.5株·m-2;D2,9.0株·m-2;D3,10.5株·m-2),研究了硝酸还原酶(Nitrate reductase,NR)活性在主茎叶位和根系的分布特点。【结果】1)不同播期和密度对叶片和根系NR活性平均值有显著影响。推迟播期对现蕾期棉花叶片与根系平均NR活性无显著影响,增加密度可降低叶片平均NR活性,但对根系平均NR活性无显著影响;推迟播期,显著降低初花期和盛花期棉花叶片NR活性平均值,但晚播对根系NR活性平均值的影响由侧根NR决定,增加密度,叶片和根系平均NR活性呈先升高后降低变化趋势,表明见花施肥后,晚播抑制了棉花地上部叶片氮代谢强度,而增强了地下部根系氮代谢强度;适度增加密度可显著增强棉花地上部叶片和地下部根系氮代谢强度。2)现蕾期叶片NR活性平均值初花期盛花期,根系NR活性平均值大体呈先升高后降低变化趋势。3)主茎叶位NR活性在3个时期均由上而下显著降低,以第1叶至第3叶波动较大,第4叶以下叶片间无显著差异,表明叶片NR活性与叶龄有关,幼叶氮代谢强度高于成熟叶片,成熟叶片之间氮代谢强度保持相对稳定。【结论】长江流域棉区(主要指湖北植棉区)棉花播种不应晚于6月14日,种植密度以9.0株·m-2最佳。     

木薯干旱胁迫下离区发育相关基因MeAP2-2酵母单杂交文库构建及其上游调控基因的筛选

为了研究干旱胁迫下调节木薯叶片脱落相关的重要节点基因及其分子调控网络,以‘华南5号’木薯为实验材料,通过采用酵母单杂交筛选系统,将MeAP2-2启动子中激素与胁迫相关的元件串联后整合入酵母染色体,构建诱饵菌株;采用SMART技术进行离区cDNA文库的构建,将离区cDNA与pGADT7-Rec表达载体共同转化诱饵菌株,通过同源重组在酵母细胞内筛选MeAP2-2的上游转录调节因子;利用酵母菌落PCR法获得阳性克隆中的cDNA插入片段,测序后在JGI网站进行Blast分析。结果表明,构建的cDNA文库库容为1.5×106,插入片段大小为250~3000 bp。cDNA 插入片段经测序和Blast同源性分析和定量PCR分析,筛选出1个Metallothionein protein,1个Core histone protein,1个Heavy-metal-associated protein与MeAP2-2相关的调节因子。实验结果证明酵母单杂交文库构建成功,初步筛选获得了调节MeAP2-2的上游调节因子。为研究木薯干旱胁迫下离区发育的信号转导通路奠定了基础。     

1-MCP partially alleviates dehydration-induced abscission in cut leaves of the fern Nephrolepis cordifolia

Fern leaves, also called fronds, are often used in bouquets. Leaves of the sword fern (Nephrolepis cordifolia) consist of a central vascular tissue, with numerous leaflets (pinnae) at each side. Leaves that have been cut and immediately placed in water show abscission of the pinnae, starting from about day 4 of vase life, with 50% pinnae abscission on day 13. The onset of pinnae abscission was hastened by a period of dehydration (3, 6, 9 or 12 h at 25 °C). The time to 50% pinnae abscission was between 7.0 and 4.7 days after 3 h and 12 h of dehydration, respectively. Dehydration treatments might induce air emboli in the xylem, but in these experiments did not inhibit water uptake. Dehydration did increase the rate of ethylene production of the cut leaves throughout vase life. A 3 h treatment with 1-MCP at concentrations of 200 or 300 nL L^?1 prior to the period of dehydration reduced the rate of ethylene production and reduced the rate of abscission. 1-MCP treatments were also effective if given after the period of dehydration. The data show that pinnae abscission limits the vase life of cut leaves of the sword fern, and that a short period of water stress drastically increases the rate of abscission. The increase in pinnae abscission was correlated with an increase in ethylene production. As 1-MCP alleviated the effect of dehydration on pinnae abscission, the dehydration effect involved ethylene perception. The data suggest that a small water stress induced an autocatalytic rise in ethylene production which was the direct cause of the increase in pinnae abscission.     

Hyperspectral Models for Estimating SPAD Value of Cotton Leaves under Waterlogging Stress

[Object] To setup the hyperspectral sensing models for estimating SPAD value of cotton leaves under waterlogging stress. [Method] Irrigation and drainage controllable plots were introduced to simulate the waterlogging stress treatment in the flowering and boll forming stage, during which the change characteristics of the cotton leaf spectral reflectance and SPAD value were observed after 1 d, 3 d, 6 d, 9 d waterlogging, respectively. To find out the hyperspectral sensing models for estimating SPAD value of cotton leaves under waterlogging stress, the correlation and regression relationships between SPAD value and spectrum parameters were analyzed. [Result] (1) The SPAD value of the fourth cotton leaf from the top was significantly lower than control when suffers from waterlogging for 3 d, when waterlogged 9 d the SPAD value decreased by around 15% compared with the control. (2) The cotton suffering from waterlogged damage in the flowering and boll forming stage caused the reflection peak in green light wave band became steep, while the near infrared spectral reflectance increased, and caused the reduction of red absorption and red edge position "blue shifts", the red edge position drifts towards short wave with 4～5 nm when suffers from waterlogging for 9 d. With increase of the waterlogged days, the red edge slope and red edge area increased with a maximum value at 6 d of waterlogging, meanwhile, the skewness and kurtosis of red edge increased. (3) After waterlogging, the SPAD value of the fourth cotton leaf from the top (chlorophyll content) had a remarkable correlation with red edge slope(Dr), red edge position(λr), green peak reflection(Rg), green peak position(λg), red well position(λo), blue edge area(SDb), yellow edge skewness(Sy), yellow edge kurtosis(Ky), red edge skewness(Sr), red edge kurtosis(Kr), etc. An experience linear, polynomial and exponential models for estimating SPAD value had been built through using the Sy, Sr, Kr as independent variables, respectively, their determination coefficient (R²) were greater than 0.9, and the root mean square error (RMSE) were less than 1; and an experience binary linear regression equation for estimating SPAD value had been built through multivariate regression using the λg, SDr/SDb(VI3), Sb, Sy, Ky as independent variables, the R² was as high as 0.973, and the RMSE was 0.393. [Conclusion] The model can be remote sensing model used as estimating leaf SPAD of cotton value under waterlogging stress.     

Diurnal carbohydrate dynamics affect postharvest ethylene responsiveness in portulaca (Portulaca grandiflora ‘Yubi Deep Rose’) unrooted cuttings

Portulaca (Portulaca grandiflora) is an herbaceous ornamental annual plant that is commonly propagated by shoot-tip cuttings and shipped long distances before they are rooted in greenhouses. During transit and rooting, a significant number of leaves usually abscise, which delays or prevents subsequent rooting. We investigated the effect of preharvest diurnal carbohydrate dynamics on postharvest performance of unrooted shoot-tip cuttings of portulaca ‘Yubi Deep Rose’. The production of ethylene was quantified, as well as the efficacy of 1-methylcyclopropene (1-MCP) to improve the postharvest performance. The initial carbohydrate concentrations in cuttings increased with later harvest during the day (8 a.m., 12 p.m., and 4 p.m.). When cuttings were placed into a dark postharvest environment at 20 ± 1 °C for 48 h, cuttings harvested at 8 a.m. had complete leaf abscission, whereas only partial leaf abscission was observed in cuttings harvested at 12 p.m. and 4 p.m. Leaf abscission was negatively correlated with preharvest leaf carbohydrate and stem starch concentrations, but not significantly correlated with postharvest ethylene production during storage. Application of 1-MCP improved the storage quality of cuttings, irrespective of the time of cutting harvest, and did not inhibit the rooting response during subsequent propagation. Collectively, these results indicate that with the increase in preharvest endogenous carbohydrate levels of portulaca cuttings, as the photoperiod progresses, subsequent postharvest ethylene responsiveness decreases, but there is no effect on ethylene synthesis.     

陆地棉GhERF8基因的克隆与表达分析

 乙烯响应元件结合因子（Ethylene-responsive element-binding factor,ERF）是植物中最大的转录因子家族之一。本研究以棉花叶片cDNA文库为基础,从陆地棉中棉所10号中克隆得到一个新的ERF基因,命名为GhERF8（GenBank：JN656957）。该基因编码265个氨基酸,蛋白序列中包含一个AP2保守结构域。采用荧光定量PCR（RT-PCR）的方法,对GhERF8基因在棉株不同生育时期叶片和不同组织中的表达水平进行了定量分析。结果表明,GhERF8基因在各组织中均有表达,但在成熟后期的叶片中表达量最高。GhERF8表达量与叶片衰老过程中叶绿素含量出现相反的变化趋势,推测GhERF8可能与叶片衰老有一定关系。在乙烯利和茉莉酸处理下GhERF8基因在叶片中上调表达,而在脱落酸处理下GhERF8表达量无显著变化,推测GhERF8可能处于乙烯和茉莉酸信号转导网络中,且表达途径为非ABA依赖途径。     

Natural variation in fruit abscission-related traits in apple (Malus)

Abscission or retention of ripening fruit is a major component of seed dispersal strategies and also has important implications for horticultural production. Abscission-related traits have generally not been targeted in breeding efforts, and their genetic bases remain mostly unknown. We evaluated 144 Malus accessions representing wild species, domestic cultivars, and hybrids for abscission-related traits. We found that seasonal timing of fruit abscission in wild species and hybrids showed a broad distribution similar to that seen for domestic cultivars, and that internal ethylene concentration at the time of abscission varied by over three orders of magnitude. Wild species, domestic cultivars, and hybrids all included representatives that showed abscission of fruit prior to substantial production of ethylene, as well as accessions that retained fruit for a significant period of time following ethylene production. For all accessions that retained fruit, fruit removal resulted in abscission of the pedicel, and exogenous ethylene promoted abscission, suggesting that the abscission zone was functional. Our results suggest important roles for mechanisms independent of fruit ethylene production in abscission.     

棉花与锦葵科等植物的子叶、叶序与花瓣旋向之间的形态相关

棉花与锦葵科（Malvaceae）等植物的子叶、真叶、花梗与花瓣的一些形态特征有着十分密切的互相关连。据对棉花与锦葵科及十字花科，茄科、苋科、藜科共5科16种植物观察，它们的二片子叶均有大小之别，并各自参预了叶序及其转向的形成。叶序转向的顺时针或反时针系由数学上或然率所致。棉花和多种锦葵科植物的主茎叶序转向与叶     

打顶后NAA处理对烟草生长、烟叶中钾和烟碱浓度的影响

在云南省田间连续三年研究了打顶后在茎断面涂抹萘乙酸（NAA）处理对烤烟植株生长、钾素吸收、烟叶中钾和烟碱浓度的影响。结果表明,打顶导致整个烟株中钾素的钾素损失,烟叶中钾浓度下降,烟碱浓度增加。打顶后NAA处理可以增加烟株对钾素的吸收,并促进钾素向叶片中分配,使叶片钾浓度提高;同时降低叶片烟碱浓度。第一次NAA处理两周后用NAA再处理一次虽然可以进一步提高烟叶钾浓度,但使叶片干重稍有下降,且在操作上多一道工序。若开花后不打顶,虽然叶片中钾浓度较高,但大大降低了叶片干物重,严重影响叶片的产量和品质。     

棉花叶片不同位点SPAD值与植株氮营养相关性研究

为了确定最能代表棉花氮素营养水平的叶片SPAD值测定位点,采用水培试验方法,设7个供氮水平,分3次测定棉花6片主叶（倒1叶至倒6叶）17个不同位点的SPAD值,对棉花不同叶位及同一叶片不同测定位点SPAD值与棉株氮素营养水平的相关关系进行研究。结果表明,倒4叶SPAD值与棉株地上部氮含量的相关性最好,相关系数为0.6524,达到了显著水平,可认定倒4叶为棉花的功能叶。而棉花倒4叶17个测定位点中,叶片上缘位置SPAD值与地上部氮含量的相关性较靠近叶柄的部位更好,其中S3位点即叶尖位置的相关系数最高,为0.4597,达极显著水平。可以初步确定棉花倒4叶叶尖位置为测定SPAD值以判断棉花氮素营养水平的最佳位点。     

田间条件下棉花叶片缺钾症状及钾含量的时空动态研究

为了探究棉花中上部叶片首先出现缺钾症状的生理机制,以中棉所41为供试材料,于2013—2014年在中国农业大学上庄实验站缺钾(K)土壤上(速效K含量64.0~70.9 mg kg–1)进行试验,设置低钾(225 kg K2O hm–2)和高钾(375 kg K2O hm–2)2个钾处理,以不施钾为对照,观察蕾期至花铃后期主茎叶缺K症状的发展动态,并测定了叶片的K+含量。结果表明,棉花叶片缺K症状并不是简单的自下部老叶逐步向上发展,而是从第10节位左右向上推移,并且这种推移呈跳跃式,植株中部某些叶位的叶片一直未出现缺K症状或症状很轻微。棉花这种缺K症状模式与叶片K+含量无必然联系。叶片K+含量基本遵循随叶位上升而增加的规律,符合缺K条件下的一般特征,但这种自下而上增加的幅度及增幅较大的部位在不同生育时期和不同年份存在差异。大部分叶片的K+含量随叶龄增长呈或快或慢的下降趋势,但在蕾期至盛花期某些幼叶和功能叶的K+含量会出现上升现象,如2013年的第7~第14叶、2014年的第13~第16叶。要揭示棉花缺K症状的生理机制,还需要从不同叶片对K+的敏感性、K+在整株水平的再分配等方面深入研究。