Effects of Reddening of Cotton (Gossypium hirsutum L.) Leaves on Functional Activity of Photosynthetic Apparatus

Strong inhibition of rates of CO₂ assimilation and transpiration, stomatal conductance, and water use efficiency as well as photosystem 2 (PS2) photochemical activity were related to the severity of reddening. The inhibition of photosynthesis in red cotton leaves was due to both decreased photochemical activity and stomatal limitation. Lowered photosynthetic capacity could be one of the main factors of reduced yield in reddening cotton.     

Reddening of Cotton (Gossypium Hirsutum L.) Leaves

Reddening of leaves is a physiological disorder in cotton induced by different abiotic stresses. Dramatic biochemical changes occurred in reddening leaves: strong accumulation of anthocyanins and drop of chlorophyll content, important increase of proline content and peroxidase activity. The lipid peroxide content indicative of membrane fragmentation was decreased. In this way a multicomponent system encompassing anthocyanins, proline, and peroxidase may act coordinately to overcome abiotic stress in cotton.     

Relationship between leaf reddening,ROS and antioxidants in <Emphasis Type="Italic">Buxus microphylla</Emphasis> during overwintering

To provide a theoretical basis for revealing the mechanism of winter leaf reddening in evergreen species, the relationships between winter leaf reddening, reactive oxygen species (ROS) and the antioxidant system of Buxus microphylla ‘Wintergreen’ were studied. The pigment changes, ROS production, lipid peroxidation and antioxidants activities of sun leaves during the reddening and regreening processes were investigated, using green shade leaves as controls. The carotenoids in the sun leaves increased linearly with reddening but decreased with the regreening. There was no significant difference in either the superoxide anions (O ₂ ^?· ) or malondialdehyde (MDA) changes between the sun and shade leaves, and their O ₂ ^?· contents were positively correlated with MDA. In contrast to the shade leaves, the sun leaves showed a trend in which the hydrogen peroxide (H₂O₂) changes were closely related to the reddening process and positively correlated with carotenoids content but not with the MDA content. A similar trend was observed for catalase (CAT) and ascorbate peroxidase (APX) activity between the sun and shade leaves, but superoxide dismutase (SOD) and peroxidase (POD) activity and the ascorbate (AsA) content differed between these two ecotypes. Furthermore, the sun leaves had higher CAT activity and AsA content than the corresponding shade leaves. These results suggested that H₂O₂ might play an important role in the winter reddening of sun leaves by promoting the accumulation of carotenoids. In addition, SOD, POD and AsA probably play a photoprotective role in winter-red sun leaves, while the changes in O ₂ ^?· , CAT and APX were independent of winter leaf reddening and were more likely responses to stress caused by low temperatures.     

茶叶叶绿体的嗜锇颗粒含量和适制茶类的关系

应用电子显微镜技术,从细胞亚显微水平研究了81个茶叶品种(或品系)的叶绿体内嗜锇颗粒的分布情况及其适制茶类的关系。结果表明,适制乌龙茶的茶树品种嗜锇颗粒含量都比较多,而有特殊香气的凌云白毛茶嗜锇颗粒含量高达100—46(平均值58),认为嗜锇颗粒含量与成茶香气有关,研究不同茶树品种的嗜锇颗粒含量可为茶树品种的成茶适制性和育成高香型品种的亲本选择提供参考依据。     

The Occurence of delta-Tocopherylquinone in Higher Plants and Its Relation to Senescence

delta-Tocopherylquinone (deltaTQ) content was determined in tobacco and yellow maple leaves, green ivy leaves and cactus tissues. It was found that the concentration of delta-TQ was highest in mature or senescent tissues, such as white tobacco leaves (0.02 mumole/g dry wt) while its detection was uncertain in young, green leaves from the apex of tobacco plants. Fractionation by centrifugation of senescent tobacco leaves showed that the osmiophilic globule fraction was enriched in delta-TQ. Electron microscope studies of young, mature and senescent tobacco tissues showed progressive changes in the size and number of osmiophilic globules. After chloroplast breakdown in senescent tobacco leaves, these globules became the predominant constituents of the organelle. delta-TQ which is associated with osmiophilic globules may play a role in the development of plants, particularly during senescence.     

表达阳离子抗菌肽的转基因棉花表型异常

用基因枪轰击茎尖法将人工合成的阳离子抗菌肽CEMA基因导入棉花中,获得3株转基因棉花,它们均出现嵌合体表型。在表型不正常的枝条上,叶片扭曲畸形,出现灰绿色与绿色条纹相间的花叶,花器发育异常、无花粉、人工授粉不能结实。花叶区的叶绿素含量降低约20％,叶肉栅栏组织细胞局部缺损,维管束及其管状分子数目减少。叶片灰绿色区叶肉细胞的次生壁明显增厚,局部区域吞噬现象明显,叶绿体内基粒片层数目较少,嗜锇小体明显较多,类囊体腔不明显。PCR分析表明,仅在不正常枝条的花叶中检测到外源CEMA基因。     

兰属春剑叶艺突变体叶片结构的研究

以兰属春剑(Cymbidium tortisepalum Fukuy.var.longibracteatum)叶色突变体‘隆昌素’及其亲本为材料,采用石蜡切片、扫描电镜及透射电镜对叶片的组织结构、扫描结构和超微结构进行了观察。结果显示,春剑叶色突变体叶片的表皮厚度和叶肉细胞面积均大于亲本,但导管数量少于亲本;叶片上、下表皮纹饰与亲本具有明显差异;气孔密度和面积均小于亲本,且气孔闭合度较大,占总气孔数的56%;突变体的叶绿体呈高密度的囊泡状结构,内部严重解体,体积较小的嗜锇滴聚集分布,无基粒片层,无淀粉粒。本研究表明经组培诱变的春剑叶色突变体的叶片结构与亲本存在明显差异。     

Mycoplasma-like Organisms in Phloem Elements of Ammobium alatum

Using transmission electron and fluorescent microscopes, Mycoplasma-like organisms (MLOs) were found in phloem cells of stems and leaves of Ammobium alatum. The diameter of these organisms ranged from 0.12–0.73 μm and averaged 0.4 μm. Symptoms induced by MLOs included chlorosis and reddening of leaves and winged stems, plant stunting and flower phyllody. This is the first report of MLOs associated with disease symptoms in A. alatum.     

Detection and Identification of Aster Yellows Group Phytoplasma (16SrI‐C) Associated with Peach Red Leaf Disease

In 2011, typical symptoms suggestive of phytoplasma infection such as reddening of leaves were observed in peach trees in Fuping, Shaanxi Province, China. Phytoplasma‐like bodies were observed by transmission electron microscope in the petiole tissues of symptomatic peach trees. Products of c. 1.2 kb were generated from all symptomatic peach leaf samples by a nested polymerase chain reaction using phytoplasma universal primer pairs P1?P7 and R16F2n?R16R2, whereas no such amplicon was obtained from healthy samples. Results of phylogenetic analysis and restriction fragment length polymorphism suggested that the phytoplasma associated with such peach red leaf disease was a member of subgroup 16SrI‐C. To our knowledge, this is the first record of 16SrI‐C subgroup phytoplasma occurred in peach tree in China.     

Anatomy of the vegetative organs and secretory structures of Rhaponticum carthamoides (Asteraceae)

Roots, stems, rhizomes and leaves of Rhaponticum carthamoides (Willd.) Iljin (a Siberian adaptogenic plant, originating from the Altai and Saian Mountains) of different ages were investigated by means of light and electron microscopy. Schizogenous secretory reservoirs occurred in every organ, and were located within the secondary xylem (adventitious roots and rhizome of young plants), at the interface of endodermis/cortical parenchyma (roots and hypocotyl), along phloem and primary xylem (older rhizome), around the vascular bundles (inflorescence stem, petiole and leaf midrib veins) and along phloem (cotyledonary and leaf veins). At the interface of endodermis/inner parenchyma, secretion accumulated in the intercellular spaces prior to the formation of proper epithelial cells. The secretion as observed by transmission electron microscopy comprised three components: soluble (i.e. absent from sections; probably phenolic), insoluble and strongly osmiophilic (probably phenolic) and insoluble, moderately osmiophilic (probably lipidic). Numerous osmiophilic oil droplets, similar to the lipidic secretion inside the reservoirs, local proliferation of rough endoplasmic reticulum and numerous multivesicular bodies characterized epithelial cells in all organs. Leucoplasts (in subterranean organs) with osmiophilic inclusions and peroxisomes with crystalloid inclusions were specific for parenchyma cells. Peltate glandular hairs were formed on leaf blades.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 144 , 207–233.     

The Occurence of δ-Tocopherylquinone in Higher Plants and Its Relation to Senescence

δ-Tocopherylquinone (δTQ) content was determined in tobacco and yellow maple leaves, green ivy leaves and cactus tissues. It was found that the concentration of δ-TQ was highest in mature or senescent tissues, such as white tobacco leaves (0.02 μmole/g dry wt) while its detection was uncertain in young, green leaves from the apex of tobacco plants. Fractionation by centrifugation of senescent tobacco leaves showed that the osmiophilic globule fraction was enriched in δ-TQ. Electron microscope studies of young, mature and senescent tobacco tissues showed progressive changes in the size and number of osmiophilic globules. After chloroplast breakdown in senescent tobacco leaves, these globules became the predominant constituents of the organelle. δ-TQ which is associated with osmiophilic globules may play a role in the development of plants, particularly during senescence.     

The Ultrastructure of Chloroplasts in Mineral-deficient Maize Leaves

The ultrastructure of mesophyll chloroplasts in full-nutrient and mineral-deficient maize (Zea mays) leaves was examined by electron microscopy after glutaraldehyde-osmium tetroxide fixation. Nitrogen, calcium, magnesium, phosphorus, potassium, and sulfur deficiencies were induced by growing the plants in nutrient culture. Distinctive chloroplast types were observed with each deficiency. Chloroplasts from nitrogen-deficient plants were reduced in size and had prominent osmiophilic globules and large grana stacks. Magnesium deficiency was characterized by the accumulation of osmiophilic globules and the progressive disruption of the chloroplast membranes. In calcium deficiency, the chloroplast envelope was often ruptured. Chloroplasts from potassium- or phosphorus-deficient plants possessed an extensive system of stroma lamellae. Sulfur deficiency resulted in a pronounced decrease of stroma lamellae, an increase in grana stacking, and the frequent occurrence of long projections extending from the body of the chloroplast. These morphological changes were correlated with functional alterations in the chloroplasts as measured by photosystem I and II activities. In chloroplasts of the nitrogen- and sulfur-deficient plants an increase in grana stacking was associated with an increase in photosystem II activity.     

Leaf diaheliotropic movement can improve carbon gain and water use efficiency and not intensify photoinhibition in upland cotton (<Emphasis Type="Italic">Gossypium hirsutum</Emphasis> L.)

Upland cotton (Gossypium hirsutum L.) can move leaves to track the sun throughout the day, so-called leaf diaheliotropic movement. This paper reports an experimental test of the hypothesis that leaf diaheliotropic movement in upland cotton can enhance carbon assimilation and not increase the risk of stress from high energy load. In this experiment, cotton leaves were divided into two groups: one was that leaves could track the sun freely; another was that leaves were retained to the horizontal position. The diaheliotropic leaves recorded higher incident irradiance than the restrained ones, especially in the morning and late afternoon. Compared with restrained leaves, diaheliotropic leaves were generally warmer throughout the day. As expected, diaheliotropic leaves had significantly higher diurnal time courses of net photosynthetic rate (P _N) than restrained leaves, except during 14:00–18:00 of the local time. Higher instantaneous water-use efficiency (WUE) was observed in diaheliotropic leaves in the early morning and late afternoon than in the restrained leaves. During the given day, diaheliotropic and restrained leaves had similar diurnal time courses of recovery of maximal quantum yield of PSII photochemistry (F_v/F_m). Diaheliotropic leaves recorded lower or similar photochemical quenching coefficient (q_p) than restrained leaves did throughout the day. These results suggest that cotton leaf diaheliotropic movement can improve carbon gain and water use efficiency and not intensify photoinhibition.     

ULTRASTRUCTURAL CHANGES OF CHLOROPLASTS IN ATTACHED AND DETACHED,AGING PRIMARY WHEAT LEAVES

Degradation of chloroplasts is shown in mesophyll cells of primary leaves of wheat. The sequence of ultrastructural changes in chloroplasts of naturally senescing leaves is compared with that of detached, aging leaves. In chloroplasts of naturally senescing leaves, the first indications of aging are the appearance of osmiophilic globuli and reorientation of the thylakoidal system. The membranes of the grana and intergrana lamellae then become distended and later dissociate into distinct vesicles. Concurrent with these membrane changes, osmiophilic globuli increase in size and number, and the stroma breaks down. Finally, the chloroplast envelope ruptures and plastid contents disperse throughout the cell's interior. In chloroplasts of mesophyll cells in detached, aging leaves, initial changes also include appearance of osmiophilic globuli, but later stages of chloroplast degradation are different. The chloroplast envelope ruptures before the lamellae break down. Swelling of grana and intergrana lamellae is not pronounced and, additionally, the thylakoidal system degenerates without forming vesicles or numerous osmiophilic globuli. These differences in the sequence of chloroplast degradation indicate that naturally senescing leaves rather than detached, aging leaves should be used in studies of chloroplast senescence.     

Contrasting patterns of sun-red and shade-green leaves of <Emphasis Type="Italic">Buxus microphylla</Emphasis> in response to gradients of excess light during winter acclimation

Leaf reddening in overwintering evergreens largely restricts their application in landscapes and is generally triggered in response to excess light. To explore how leaves respond to excess light and examine the potential relevance of leaf reddening in this process, a comparative field study was conducted on the sun leaves (SUL), shade leaves (SHL) and three levels of artificially shaded sun leaves (SSUL) of Buxus microphylla ‘Wintergreen’. The seasonal changes in leaf colorations, chlorophyll (Chl) and carotenoid contents, leaf absorbance and chlorophyll fluorescence characteristics were investigated. The results showed that SUL upregulated Chl a/b with increased reductions in Chl b compared with Chl a, accumulated red pigments in the upper palisade mesophyll with reduced absorption in blue and red light but increased absorption in green light, and additionally, significantly downregulated photochemical activities through the sustained enhancement of energy dissipation in PSII antenna (ΦD) from fall to midwinter. In the SSUL, as the light intensity decreased, all of the above processes were mitigated except that the SSUL maintained constant absorptions in blue light region and whose levels were similar to those of the SUL and SHL. In contrast, the SHL maintained relatively high levels of Chl a and Chl b, remained completely green and showed regulated ΦD and ΦE (energy dissipation in PSII reaction centers) to maintain relatively high photochemical activity in the winter. We conclude that the sun leaves downregulate Chl contents to reduce the light absorption and simultaneously enhance sustained ΦD to dissipate most of the light energy, whereas shade leaves maintain relatively high Chl contents and demonstrate regulated proportions of ΦD and ΦE to match the extent to which the absorbed light can be utilized through photochemical reactions. The accumulated red pigments in sun phenotypes may provide a shading effect on Chls by directing energy to non-photosynthetic reaction centers in the blue light region where the absorption is offset by the reduced Chls.     

田间条件下海岛棉和陆地棉花铃期叶片光保护的机制

研究海岛棉(Gossypium barbadense)和陆地棉(G. hirsutum)两个棉花栽培种的光合作用特性, 探讨两个栽培种光合机构的光抑制以及防御保护机制, 以期为新疆棉花高光效品种选育和高产高效栽培实践提供理论基础。在新疆生态气候条件下, 系统测定了海岛棉和陆地棉的叶片运动、叶片接受光量子通量密度(PFD)、叶片温度、叶绿素荧光参数、气体交换参数和光呼吸速率的日变化。研究结果表明: 陆地棉叶片的“横向日性”较强而海岛棉较弱, 导致海岛棉叶片接受PFD较低, 但其叶片温度较高。海岛棉叶片的光合速率和气孔导度均显著低于陆地棉。在8:00-10:00 (北京时间, 下同)海岛棉叶片的光呼吸速率略低于陆地棉, 其余时间段海岛棉和陆地棉叶片的光呼吸速率相似。不同栽培种间, 叶片的最大光化学效率和实际光化学效率的日变化均无明显差异。除14:00-16:00以外, 海岛棉叶片的表观电子传递速率和光化学猝灭系数均显著低于陆地棉。8:00以后, 海岛棉叶片的非光化学猝灭显著高于陆地棉。因此, 在新疆生态气候条件下, 海岛棉和陆地棉叶片“横向日性”运动能力和气孔导度的差异导致叶片所处的光温环境不同, 同时造成海岛棉叶片的碳同化能力较低。为阻止光合电子传递链的过度还原, 减轻光合机构的光抑制, 陆地棉叶片主要通过光合机构的电子流途径耗散激发能, 而海岛棉叶片通过热耗散途径和相对较高的光呼吸能力来耗散激发能。     

Electron microscopical and autoradiographical studies on the so-called yolk-nuclei in the oocytes of Nemacheilus barbatulus (L.) and Phoxinus phoxinus (L.) (Pisces, Teleostei) (author's transl)

The yolk-nuclei in the oocytes of the teleosts Noemacheilus barbatulus (L.) and Phoxinus phoxinus (L.) were investigated by electron microscopy, autoradiography and ultrahistochemistry. Yolk-nuclei were only found in stage I. They consist of mitochondria, an osmiophilic material and in Noemacheilus partly of dictyosomes. It was demonstrated by marking with [3H]-uridine, that the osmiophilic material contains RNA. The osmiophilic material gets into the juxtanuclear cytoplasm. There it is surrounded by mitochondria. The oocytes of Noemacheilus and Phoxinus contain up to 40 yolk-nuclei, which are only visible by electron microscopy. The yolk-nuclei of both species dissolve in early stage II. Their components disperse in the cytoplasm.     

Ultrastructural Studies on the Development of Oil Cells in Litsea pungens

The developmental process of oil cells in the shoot of Litsea pungens Hemsl. has been studied with transmission electron microscopy. According to the development of the three layers of cell wall, the developmental process could be divided into 4 stages. In stage 1, the cell wall consisted only of a primary (the outmost) cellulose layer, which might further be divided into two substages, the oil cell initial, and the vacuolizing oil cell. During this stage, there were some small electron translucent vesicles and dark osmiophilic droplets of variant sizes in the different-shaped plastids. It was observed that some dark and gray osmiophilic materials coalesced to vacuoles in the cytoplasm. In stage 2, a lamellated suberin layer accumulated inside the primary cellulose layer. In stage 3, a thicker and looser inner cellulose wall layer was formed gradually inside the suberin layer. Some dark osmiophilic droplets have been observed in this loose inner cellulose wall layer. The plasmodesmata were blocked up and became a special structure. Then, the big vacuole, which is the oil sac, was full of osmiophilic oil. In stage 4, the oil cell became matured and the cytoplasm disintegrated. The oil sac enveloped from plasmalemma was attached to the cupule, which was formed by the protuberance of the inner cellulose wall layer into the lumen. After the maturity of oil cell, the ground cytoplasm began to disintegrate and became electron opaque or exhibited in a disordered state, and the osmiophilic oil appeared light gray.     

木姜子油细胞发育的超微结构研究

利用超薄切片法和透射电镜研究了木姜子（Litsea pungens Hemsl.）油细胞的发育过程。油细胞3层细胞壁的发育可分为4个阶段,阶段1：油细胞仅有初生纤维素壁层,又可分为原始细胞和细胞 泡化两个时期。此阶段质体具透明小泡和黑色嗜锇物质,并与液泡融合。阶段2：木栓质化壁层的形成,片层状木栓质不断叠加在初生纤维素壁内侧,其细胞结构与前期相似,阶段3：内纤维素壁层的形成,较厚而松散的内纤维素壁层叠加在木栓质化壁层的内侧,在内纤维素壁层中可见黑色嗜锇物质,胞间连丝成为被阻塞的特化结构,此时大液泡被嗜锇油脂充满,成为油囊。阶段4：油细胞成熟及细胞质解体,杯形构造由内纤维素壁层向细胞腔内突起形成,油囊由液泡膜包被连接到杯形构造上,油呈浅灰色嗜锇状态,其细胞质和细胞器解体,变得电子不透明或呈杂乱状态。     

Circumvention of over-excitation of PSII by maintaining electron transport rate in leaves of four cotton genotypes developed under long-term drought

We investigated the patterns of response to a long-term drought in the field in cotton cultivars (genotypes) with known differences in their drought tolerance. Four cotton genotypes with varying physiological and morphological traits, suited to different cropping conditions, were grown in the field and subjected to a long-term moderate drought. In general, cotton leaves developed under drought had significantly higher area-based leaf nitrogen content (N (area)) than those under well irrigation. Droughted plants showed a lower light-saturated net photosynthetic rate (A (sat)) with lower stomatal conductance (g (s)) and intercellular CO (2) concentration (C (i)) than irrigated ones. Based on the responses of A (sat) to g (s) and C (i), there was no decreasing trend in A (sat) at a given g (s) and C (i) in droughted leaves, suggesting that the decline in A (sat) in field-grown cotton plants under a long-term drought can be attributed mainly to stomatal closure, but not to nonstomatal limitations. There was little evidence of an increase in thermal energy dissipation as indicated by the lack of a decrease in the photochemical efficiency of open PSII (F (v)'/F (m)') in droughted plants. On the basis of electron transport (ETR) and photochemical quenching (q (P)), however, we found evidence indicating that droughted cotton plants can circumvent the risk of excessive excitation energy in photosystem (PS) II by maintaining higher electron transport rates associated with higher N (area), even while photosynthetic rates were reduced by stomatal closure.