Photosynthesis, Morphology, Leaf Anatomy, and Cytogenetics of Hybrids between C(3) and C(3)/C(4)Panicum Species

The Laxa group of the Panicum genus contains species which have CO₂ exchange and anatomical characteristics intermediate to C₃ and C₄ photosynthetic types (C₃/C₄), and also species characterized as C₃. Hybrids were made between two of the C₃/C₄ species and two C₃ species. Carbon dioxide exchange and morphological, leaf anatomical, and cytogenetic characteristics of F₁ hybrids between Panicum milioides Nees. ex Trin (C₃/C₄) and P. laxum Mez. (C₃), P. spathellosum Doell (C₃/C₄) and P. boliviense Hack. (C₃), and P. spathellosum and P. laxum were studied. There were no consistent differences in apparent photosynthesis, although two of the three hybrids had higher net CO₂ uptake than the C₃ parent. Values of inhibition of apparent photosynthesis by 21% O₂, CO₂ loss in the light, and CO₂ compensation concentration for the hybrids were between those of the parents. All three hybrids showed leaf anatomical traits, especially organelle quantities in the bundle sheath cells, between those of their respective parents. Linear regression of CO₂ compensation concentration on the percentage of mitochondria and chloroplasts in vascular bundle sheaths of the parents and hybrids gave correlation coefficients of −0.94. This suggests that the reduction in CO₂ loss in the C₃/C₄ species, and to a lesser degree in the F₁ hybrids, was due to development of organelles and perhaps a higher proportion of leaf photorespiration in bundle sheaths. The overall morphology of the hybrids was so different from the parents that they could be described as new taxonomic forms. The chromosomes in the hybrids were mainly unpaired or paired as bivalents indicating possible homology between some parental genomes.     

Photosynthesis, Leaf Anatomy, and Morphology of Progeny from Hybrids between C(3) and C(3)/C(4)Panicum Species

Species in the Laxa group of Panicum have C₃ or C₃/C₄ photosynthesis based on leaf anatomical and CO₂ exchange characteristics. Hybrids were previously made between C₃/C₄ and C₃ species in this group (RH Brown et al. 1985 Plant Physiol 77: 653-658). In this paper, CO₂ exchange, morphological, and leaf anatomical characteristics of F₂ or F₅ progeny from colchicine-induced amphiploids of C₃/C₄ × C₃ hybrids (Panicum milioides Nees ex Trin. [C₃/C₄] × Panicum laxum Mez [C₃] and Panicum spathellosum Doell [C₃/C₄] × Panicum boliviense Hack. [C₃]) were studied.

There were no differences found in morphology or physiology between the amphiploids and the F₁ hybrids from which they were produced. In the segregating progeny, CO₂ compensation concentration and photorespiration values typical of C₃, but not of C₃/C₄ plants, were recovered. Progeny were found from both crosses which possessed O₂ inhibition of apparent photosynthesis typical of the parents, and in the case of the P. milioides × P. laxum cross, leaf anatomy and overall plant morphology typical of the parents were observed in some progeny. The progeny were found to possess recombinations of various traits associated with reduced photorespiration, so that no correlation existed among O₂ inhibition of apparent photosynthesis, CO₂ compensation concentration, and leaf anatomical traits. One plant was especially noteworthy in possessing leaf anatomy typical of C₃/C₄ plants, but with CO₂ exchange characteristics of C₃ plants.

     

Variations in the Leaf Anatomy among some C4 Panicum Species

The Dichotomiflora group of Panicum contains NAD-malic enzyme(ME) species with centrifugal chloroplasts in Kranz cells, NAD-ME(F)species as well as NAD-ME species with centripetal chloroplastsin Kranz cells, NAD-ME (P) species. Many attributes of leafanatomy of 22 C₄ Panicum species were investigated to identifydifferences among four different C₄ subtypes, i.e. NADP-ME,NAD-ME(F), NAD-ME(P) and PEP-CK species grouped by the C₄-aciddecarboxylating enzymes and chloroplast location in Kranz cellsin combination. Differences were found in the number of Kranzcells surrounding a large vein, and the number surrounding asmall vein, the interveinal distances, the proportion of leafcross sectional area occupied by epidermis plus sclerenchyma,by mesophyll cells, by Kranz cells, and by vascular bundles.There were also differences in the ratios of the area of thedifferent cell types. The number of the characters significantlydifferent between a respective pair of C₄ subtypes was the largestbetween NAD-ME(F) and NAD-ME(P) species. In principal componentanalysis applied to 11 leaf anatomical characters, the differentC₄ subtypes clustered into small groups, although the rangeof variations of PEP-CK species and those of NAD-ME(F) speciesoverlapped. The results were discussed in relation to taxonomyand ecological adaptation of Panicum species in the differentC₄ subtypes. C₄ photosynthesis, NADP-malic enzyme, NAD-malic enzyme, Phosphoenolpyruvate carboxykinase, C₄ leaf anatomy, Panicum, Kranz, Dichotomiflora group     

石蒜属12 种植物叶片比较解剖学研究

 对石蒜属( Lycoris Herb. ) 12 种植物叶片的比较解剖学研究表明: (1) 石蒜属植物叶片横切面的端部、中部及基部的轮廓基本呈浅“W”或“V”字型, 有些种的表皮细胞上具有明显的尖刺状乳突; ( 2)石蒜属植物均为异面叶, 叶肉组织有一定的栅栏组织和海绵组织分化, 但二者的厚度、叶肉中所占比例及栅栏组织的细胞层数在种间有一定的差异; (3) 海绵组织发达、具有大而明显的薄壁细胞或细胞裂溶后形成空腔(分泌腔或气腔); (4) 叶片中维管束数目大多为奇数, 叶脉维管束鞘由薄壁细胞组成; (5) 石蒜属植物横切面上叶缘的形状分为圆弧形和楔形两种类型。石蒜属植物叶的解剖结构具有许多相似特征; 同时又具有一定的种间差异, 可为石蒜属植物的种间关系和开发利用提供有价值的信息。     

石蒜属12种植物叶片比较解剖学研究

对石蒜属（Lycoris Herb．）12种植物叶片的比较解剖学研究表明：（1）石蒜属植物叶片横切面的端部、中部及基部的轮廓基本呈浅“W”或“V”字型,有些种的表皮细胞上具有明显的尖刺状乳突;（2）石蒜属植物均为异面叶,叶肉组织有一定的栅栏组织和海绵组织分化,但二者的厚度、叶肉中所占比例及栅栏组织的细胞层数在种间有一定的差异;（3）海绵组织发达、具有大而明显的薄壁细胞或细胞裂溶后形成空腔（分泌腔或气腔）;（4）叶片中维管束数目大多为奇数,叶脉维管束鞘由薄壁细胞组成;（5）石蒜属植物横切面上叶缘的形状分为圆弧形和楔形两种类型。石蒜属植物叶的解剖结构具有许多相似特征;同时又具有一定的种间差异,可为石蒜属槽物的种间关系和开发利用提供有价值的信息。     

Effects of Elevated Atmospheric CO2 Concentration on Leaf Anatomy and Morphology in Panicum Species Representing Different Photosynthetic Modes

Panicum tricanthum Nees, Panicum antidotale Retz., and Panicum decipiens Nees ex Trin. were selected to represent C3, C4, and C3/C4 intermediate perennial species of Panicum, respectively. Plants grown from seed with 900 ppm [CO2] under natural sunlight and controlled temperatures (30 degrees /22 degrees C) were compared with plants grown with ambient [CO2]. The anatomy of the last fully expanded leaf of the main tiller was studied by light microscopy with computerized graphic image analysis and by transmission electron microscopy. Leaf anatomy did not change qualitatively in response to elevated [CO2], but there were changes in leaf thickness and in the proportions of total transsectional area occupied by mesophyll, bundle sheath cells, vascular elements, and sclerenchyma, according to species. The abaxial stomatal frequency decreased by 22% for P. tricanthum but increased by ca. 30% for the other two species. With 900 ppm CO2, all three species showed a considerable increase in leaf starch content (to >30% of dry matter). Starch granules accumulated in chloroplasts of the mesophyll and bundle sheath cells. Increased leaf glaucousness in response to elevated [CO2] was the result of increased or modified deposition of epicuticular wax on both leaf surfaces, a response to elevated [CO2] that is unusual and one that has not been previously recorded for monocotyledons. The wax patterns were studied by scanning electron microscopy. Panicum decipiens did not respond to elevated [CO2] in a truly intermediate fashion; its responses resembled those of either the C3 or the C4 species. C3/C4 intermediates may thus be interpreted as developmental chimeras and not as species in transition between C3 and C4 modes in an evolutionary sense.     

Photosynthetic efficiency of Panicum hians and Panicum milioides in relation to C3 and C4 plants

Panicum hians and Panicum milioides were found to have characteristicsintermediate to those of C₃ and C₄ species with respect to CO₂compensation point, percentage inhibition of photosynthesisby O₂ at various O₂/CO₂ solubility ratios, and water use efficiency.C₄ species have a higher carboxylation efficiency than eitherthe intermediate or C₃ species. During photosynthesis, evenunder 2.5% O₂, C₄ species have a higher affinity for intercellularCO₂ (Km 1.6 µM) apparently due to the initial carboxylationthrough PEP carboxylase. Under low O₂ the intermediate and C₃species had a similar affinity for intercellular CO₂ duringphotosynthesis (Km 5–7 µM) consistent with carboxylationof atmospheric CO₂ through RuDP carboxylase. There were considerablevariation in photosynthesis/unit leaf area at saturating CO₂levels in the species examined which in part is due to differencesin RuDP carboxylase /unit leaf area. The highest rates of photosynthesis/unitleaf area under CO₂-saturating conditions were with the C₃ specieswhich had a correspondingly high level of RuDP carboxylase/unitleaf area. Possibilities for the greater efficiency of P. hiansand P. milioides in comparison to C₃ species in utilizing lowlevels of CO₂ in the presence of atmospheric O₂ are discussed. ¹ This research was supported by the College of Agriculturaland Life Sciences, University of Wisconsin, Madison; and theUniversity of Wisconsin Research Committee with funds from theWisconsin Alumni Research Foundation. (Received June 25, 1977; )     

木兰属叶片的比较解剖学研究

对木兰属（Magnolia)12种、1亚种植物的叶片进行了比较解剖学研究。结果表明：（1）Nootboom系统的云南木兰（M.yunnanensis)和乐东木兰（M.lotungensis)的叶肉中含有大量的单宁,与木兰属其他植物叶片的解剖结构有较大区别,支持刘玉壶系统^[2]拟单性木兰属（Parakmeria)的建立;（2）凹叶厚朴（M.officinalis ssp.biloba)为厚朴（M.officinalis)的亚种,二者下表皮均被表皮毛,但表皮毛的细胞个数明显不同,因而很易区分;（3）木兰属植物的叶片在叶片厚度、栅栏组织和海绵组织厚度的比例、表皮毛、油细胞大小及其分布密度密度等方面在种间具有一定差别。     

Effects of irradiance and temperature on photosynthesis in C3, C4 and C3/C4 Panicum species

Species in the Laxa and Grandia groups of the genus Panicum are adapted to low, wet areas of tropical and subtropical America. Panicum milioides is a species with C₃ photosynthesis and low apparent photorespiration and has been classified as a C₃/C₄ intermediate. Other species in the Laxa group are C₃ with normal photorespiration. Panicum prionitis is a C₄ species in the Grandia group. Since P. milioides has some leaf characteristics intermediate to C₃ and C₄ species, its photosynthetic response to irradiance and temperature was compared to the closely related C₃ species, P. laxum and P. boliviense and to P. prionitis. The response of apparent photosynthesis to irradiance and temperature was similar to that of P. laxum and P. boliviense, with saturation at a photosynthetic photo flux density of about 1 mmol m^-2 s^-1 at 30°C and temperature optimum near 30°C. In contrast, P. prionitis showed no light saturation up to 2 mmol m^-2 s^-1 and an optimum temperature near 40°C. P. milioides exhibited low CO₂ loss into CO₂-free air in the light and this loss was nearly insensitive to temperature. Loss of CO₂ in the light in the C₃ species, P. laxum and P. boliviense, was several-fold higher than in P. milioides and increased 2- to 5-fold with increases in temperature from 10 to 40°C. The level of dark respiration and its response to temperature were similar in all four Panicum species examined. It is concluded that the low apparent photorespiration in P. milioides does not influence its response of apparent photosynthesis to irradiance and temperature in comparison to closely related C₃ Panicum species.Abbreviations AP apparent photosynthesis - I CO₂ compensation point - gl leaf conductance; gm, mesophyll conductance - PPFD photosynthetic photon flux density - PR apparent photorespiration rate - RuBPC sibulose bisphosphate carboxylase     

Distribution of enzymes related to C3 and C4 pathway of photosynthesis between mesophyll and bundle sheath cells of Panicum hians and Panicum milioides

Enzymes of the C₄, C₃ pathway and photorespiration have beenanalyzed for P. hians and P. milioides, which have chlorenchymatousbundle sheath cells in the leaves. On whole leaf extracts thelevels of PEP carboxylase are relatively low compared to C₄species, RuDP carboxylase is typical of C₃ species, and enzymesof photorespiratory metabolism appear somewhat intermediatebetween C₃ and C₄. Substantial levels of PEP carboxylase, RuDPcarboxylase, and photorespiratory enzymes were found in bothmesophyll and bundle sheath cells. Low levels of C₄-acid decarboxylatingenzymes may limit the capacity for C₄ photosynthesis in P. hiansand P. milioides. The results on enzyme activity and distributionbetween mesophyll and bundle sheath cells are consistent withCO₂ fixation via C₃ pathway in these two species. ¹ This research was supported by the College of Agriculturaland Life Sciences, University of Wisconsin, Madison; and bythe University of Wisconsin Research Committee with funds fromthe Wisconsin Alumni Research Foundation; and by the NationalScience Foundation Grant BMS 74-09611. (Received September 16, 1975; )     

新疆大帽藓属6种植物茎及叶的比较解剖学研究

运用石蜡切片和电镜技术,对新疆的6种大帽藓属（Encalypta Hedw.）植物的茎和叶进行解剖学观察。结果表明：高山大帽藓（E.alpina Smith.）疣多呈菱形或“柱状”密集着生在叶表面,疣上纹饰呈纵棱和小疙瘩状;裂瓣大帽藓（E.ciliata Hedw.）茎横切面为五角形, 中轴细胞角隅加厚,叶腹面的粗疣大部分集中分布在凹陷的表面细胞壁上;剑叶大帽藓（E.spathulata C.Mull.）茎横切面没出现中柱鞘,疣在基部分叉丛生,叶腹面的表皮细胞壁不凹陷;钝叶大帽藓（E.vulgaris Hedw.）没有叶尖,中肋导水细胞大,叶表面细胞壁较光滑且强烈凹陷,其壁上的乳突不明显;天山大帽藓（E.tianschanica j.c.Zhao,R.L.Hu et S.He）茎内外皮层区分明显,内皮层细胞质浓,叶背面的分叉状粗疣呈密集生长在叶腹面的星状粗疣大多集中分布在稍下陷的细胞壁上;西藏大帽藓（E.tibetana C.Mull）中肋细胞壁加厚,叶片具层层叠叠的、密集的、不规则分叉的粗疣,叶背面有些部位被带状附属物所覆盖。这6种植物叶的背、腹面均具不同程度的分叉粗疣,但粗疣的大小、着生位置、呈现的状态、疣上不同的纹饰却各不相同;中肋细胞的层数、及导水主细胞的大小、状态也大不相同,这些细微特征的观察研究可作为大帽藓属植物分类学的依据之一。     

Regulation of Electron Transport in Photosystems I and II in C3, C3-C4, and C4 Species of Panicum in Response to Changing Irradiance and O2 Levels

Regulation of the quantum yields of linear electron transport and photosystem II photochemistry ([phi]II) with changing irradiance and gas-phase O2 concentration was studied in leaf tissue from Panicum bisulcatum (C3), Panicum milioides (C3-C4), and Panicum antidotale (C4) at 200 [mu]bars of CO2 and 25[deg]C using infrared gas analysis and chlorophyll fluorescence yield measurements. When the O2 level was increased from 14 to 213 mbars at high irradiance, [phi]II increased by as much as 115% in P. bisulcatum but by no more than 17% in P. antidotale. Under the same conditions [phi]II increased to an intermediate degree in P. milioides. Measurements of accumulation of the photooxidized form of the photosystem I reaction center (P700+) based on the light-dependent in vivo absorbance change at 830 nm indicate that the steady-state concentration of P700+ varied in an antiparallel manner with [phi]II when either the irradiance or O2 concentration was changed. Hence, O2-dependent changes in [phi]II were indicative of variations in linear photosynthetic electron transport. These experiments revealed, however, that a significant capacity was retained for in vivo regulation of the apparent quantum yield of photosystem I ([phi]I) independently of [phi]II+ Coordinate regulation of quantum yields of photosystems I and II (expressed as [phi]I:[phi]II in response to changing irradiance and O2 level differed markedly for the C3 and C4 species, and the response for the C3-C4 species most closely resembled that observed for the C4 species. The fraction of total linear electron transport supporting photorespiration at 213 mbars of O2 was negligible in the C4 species and was 13% lower in the C3-C4 species relative to the C3 species as calculated from fluorescence and gas-exchange determinations. At high photon-flux rates and high O2 concentration, the potential benefit to light use for net CO2 uptake arising from lower photorespiration in P. milioides was offset by a reduced capacity for total CO2- and O2-dependent noncyclic electron transport in this species compared with P. bisulcatum.     

番荔枝科植物叶的比较解剖学

利用扫描电镜、叶表皮离析法和石蜡切片法研究了番荔枝科93种2变种植物叶片的形态结构.结果表明番荔枝科植物叶片形态结构具有较大相似性,如叶表面均具有表皮毛,表皮细胞具有晶体,气孔器为平列型,具2～6个副卫细胞,仅分布在远轴面,普遍具有败育气孔器,叶肉组织中普遍含有油细胞等,但表皮毛的类型,表皮细胞的形状,表皮细胞内晶体的类型和形态,叶肉组织的结构具有明显的属间和种间差异.     

Effect of varying environments on photosynthetic parameters of C3, C3-C4 and C4 species of Panicum

Summary CO₂ exchange characteristics and the activity of the carboxylating enzymes phosphoenolpyruvate carboxylase (PEP-C, E.C. 4.1.1.31) and ribulose 1,5-bisphosphate carboxylase (RuBP-C, E.C. 4.1.1.39) during one year in the greenhouse and at two levels of light and temperature in growth chambers were determined in the C₃-C₄ intermediate species P. milioides Nees ex. Trin. These results were compared with those of P. bisulcatum Thumb. (C₃) and P. maximum Jacq. (C₄). Under all tested conditions, and even when the influence of leaf surface temperature on photosynthetic rates and CO₂ compensation points were measured, the biochemical and physiological behaviour of the C₃-C₄ intermediate was more similar to that of the C₃ plant than the C₄ species. The C₄ plant P. maximum, however, responded positively, mainly in terms of PEP-C activity and photosynthetic rate, to the regime of high light and temperature. The results presented indicate that in the C₃-C₄ Panicum grown in high light and temperature no direct relationships between a low CO₂ compesation point and superior growth are evident. It has still to be clarified why in nature a photosynthetic-photorespiratory pathway leading to an intermediate CO₂ compensation value has evolved in P. milioides.     

Effect of Low Relative Humidity on {delta}13C Value in Two C3 Grasses and in Panicum milioides, a C3-C4 Intermediate Species

When grown under conditions of low relative humidity, the C₃–C₄intermediate Panicum milioides, as well as the C₃ grasses Triticumaestivum and Poa pratense, exhibited ¹³C values which were upto 2–7%o less negative than the ¹³C values of the correspondingplants grown at high relative humidity. At both humidity levels,there was no evidence of a substantial contribution of phosphoenolpyruvatecarboxylase to carbon gain in Panicum milioides     

陕西4个漆树品种外部形态及次生韧皮部结构的比较

采用形态观测和石蜡切片对陕西4个漆树品种的外部形态和树皮次生韧皮部的组织结构进行了比较分析.结果表明:4个漆树品种间在树冠、树高、皮孔形状和排列方式、复叶的小叶数及总叶柄、叶轴和叶脉上的被毛等外部形态性状上差异明显;品种间树皮基本结构相同,次生韧皮部结构和组成相似,其差异主要表现在筛管直径大小、乳汁道直径大小及单位面积内数量、石细胞群大小及单位面积内数量、有/无功能韧皮部厚度之比等方面.     

Mycorrhizal symbiosis induces plant carbon reallocation differently in C3 and C4 Panicum grasses

Plant and Soil - Although arbuscular mycorrhizal symbiosis is common in many plants with either C3 or C4 photosynthesis, it remains poorly understood whether photosynthesis type has any significant...