Abnormal chromosomes and DNA content in micropropagated rhubarb (<Emphasis Type="Italic">Rheum rhaponticum </Emphasis>L<Emphasis Type="Italic">.</Emphasis>) PC49

Rhubarb (Rheum rhaponticum L.) is a tetraploid (2n = 44) vegetable crop growing in Europe and North America. The results observed 44 chromosomes for both cultivars Timperly Early and PC49, but showing significant differences in DNA contents between them. Abnormal chromosome numbers (2n = 22 and 32) and chromosomal fragments were observed only in micropropagated plants of rhubarb PC49, suggesting somaclonal variation. The results provide further information on understanding morphological variation and increased disease susceptibility of micropropagated rhubarb PC49 in our previous investigation.     

Comparative study of morphological parameters of Grand Nain banana (<Emphasis Type="Italic">Musa</Emphasis> AAA) after <Emphasis Type="Italic">in vitro</Emphasis> multiplication with growth retardants

Variation in morphological traits and increased disease susceptibility were observed in micropropagated plants of rhubarb (Rheum rhaponticum L.), PC49. Our investigations have demonstrated that micropropagated plants can vary substantially in morphological traits and the variation of quantitative traits was substantially greater than conventionally propagated plants. Micropropagated plants produced significantly more leaves than conventional plants under the same growth period, with a more bushy growth habit and/or recumbence. A higher incidence of disease (petiole spotting) was also observed in micropropagated plants. It is concluded that micropropagated PC49 had substantially higher incidence of somaclonal variation and regenerants were not suitable to establish an economic crop comparable to the conventional plants.     

Detection of genetic variation among micropropagated tea [Camellia sinensis (L.) O. Kuntze] by RAPD analysis

Summary Randomly amplified polymorphic DNA (RAPD) techniques were applied to assess genetic instability among micropropagated tea [Camellia sinensis (L.) O. Kuntze] eultivar ‘T-78’. Out of 49 random 10-mer primers, 11 generated polymorphism in four out of 17 micropropagated plants and one mother plant. A total of 221 bands, ranging from 525 bp to 2.5 kb, were produced by the 49 primers. Twenty-four were polymorphic for those four plants. However, the remaining bands were monomorphic among all plants. Polymorphism among those four plants showed an identifical banding pattern suggesting the occurrence of a single mutation. Our results demonstrated that RAPD can be used successfully to determine the genetic instability among micropropagated plants which otherwise were morphologically indistinguishable.     

Stomatal physiology of a micropropagated CAM plant; Agave tequilana (Weber)

Experiments were designed to assess the capacity of an in vitro cultured CAM plant to control water loss and to examine the response of their stomata to various factors. Detached leaves of micropropagated Agave tequilana plants lost water at similar rates as did field-grown plantlets when dehydrated in air. This was consistent with the fact that stomata from micropropagated plants show similar morphology than field-grown plantlets. In addition, stomata from micropropagated plants responded to various factors in a manner similar to those from field-grown plantlets. It appears that in vitro culture does not affect the capacity of leaves to control water loss nor does it alters the nocturnal stomatal opening of this CAM plant.     

亚热带森林附生植物叶片气孔特征及其可塑性对光照变化的响应

附生植物是热带亚热带森林生态系统中物种多样性极高且极其脆弱敏感的生物类群之一。光照被认为是促进附生植物由陆生类群演化而来并决定其生长和分布的关键因素。然而,由于接近林冠和规范性采样的限制,附生植物与光照的关系仍亟待阐述。为揭示附生植物对光强变化的响应和适应策略,该研究以亚热带常绿阔叶林6种附生植物(林冠层木本:鼠李叶花楸、毛棉杜鹃;林冠层草本:狭瓣贝母兰、毛唇独蒜兰;树干区草本:点花黄精、距药姜)为对象,对其在4个光处理梯度下生长的叶片气孔特征及其可塑性进行了对比分析。结果表明:(1) 2种附生小乔木的气孔面积(SA)、气孔密度(SD)、潜在气孔导度指数(PCI)和表皮细胞密度(ECD)均对光强改变显著响应。2种附生兰科植物的SA最大,而SD最小;附生乔木叶片SD和ECD的光响应趋势与陆生植物更相似,而附生草本则出现种间差异。(2) 6种附生植物的气孔、表皮细胞特性及其表型可塑性,在草本-木本、常绿-落叶植物、林冠-树干区之间,均无明显差别。(3)附生植物气孔特性和表皮细胞平均可塑性指数均低于陆生植物。综上结果表明,亚热带常绿阔叶林中附生植物对于光环境变化的适应性相对较弱。不同的附生植物可以通过不同程度地增加叶片SD和ECD来适应高光强生境,并通过对SD和SA的双重调节以增大潜在光合能力从而应对低光胁迫。     

Failure of sexual reproduction found in micropropagated critically endangered plants prior to reintroduction: a cautionary tale

Micropropagation is a useful technique for ex situ multiplication and restoration of critically endangered plant species, but the sexual reproductive behaviour of micropropagated plants is seldom evaluated prior to reintroduction. We examined the critically endangered species Rulingia sp. ‘Trigwell Bridge’, with only three remaining plants known in the wild, as a model case to examine this issue. Abnormalities in micropropagated plants of this species related to four floral traits (lengths of sepals, petals and anthers and width of anthers). The number of pollen grains per flower of abnormal individuals was lower than in plants with apparently normal flowers (wild types), but not significantly so (P = 0.068). Pollen viability for the abnormal plant (0.87 ± 0.26%) was significantly lower than for the plants exhibiting wild‐type floral morphology (45.42 ± 4.47%). Experimental manipulations were used to examine the mating behaviour of normal and abnormal plants. The results showed that both male and female reproductive failure was linked to individuals exhibiting abnormal flowering attributes. Such aberrant reproductive performance in a micropropagated rare species predicates caution when using micropropagated plants in reintroduction programmes, highlighting the importance of screening for reproductive normality prior to release of micropropagated plants (especially for critically endangered species where reliance on in vitro propagation methods is often a necessity). © 2011 The Linnean Society of London, Botanical Journal of the Linnean Society, 2011, 165 , 278–284.     

菠萝蜜白化突变体叶片表皮形态研究

为探究木本植物白化突变体叶片表皮形态的变化,在扫描电镜下观测了菠萝蜜（Artocarpus heterophyllus）白化突变体（AAS）和正常（CK）幼苗叶片的表皮细胞和气孔器,对MAP65家族蛋白构建了进化树,并分析了MAP65基因的表达模式。结果表明,AAS表皮细胞和气孔器的大小、形态均发生较大变化。与CK相比,AAS表皮细胞的周长、面积较小,密度较大,凸出数量和长度均减少,气孔器较小且大小不一。下表皮小细胞和异常气孔器的数量在AAS中大幅增加。MAP65家族成员大部分基因在AAS中下调表达。因此,推测菠萝蜜白化突变体的发生可能与MAP65基因表达有关。     

Leaf morphological plasticity and stomatal conductance in three Populus alba L. genotypes subjected to salt stress

The effect of salt stress on leaf morphology and functionality was studied in three Populus alba genotypes differing in tolerance to salinity: 6K3 (sensitive), 2AS11 (moderately tolerant), and 14P11 (tolerant). Plants were subjected to an intense and progressive salt stress from 50 to 250 mM NaCl by 50 mM steps at 10-day intervals. The micromorphological results highlighted phenotypic variation among the three genotypes already in control plants, with the genotype 14P11 having significantly smaller epidermal cells and higher stomatal density. Salt-treated plants modulated differently the expansion of stomata compared with epidermal cells. Regression analysis showed significant correlations between decrease of stomatal area and stomatal conductance (g_s) in genotypes 14P11 and 6K3. So, the common reduction of stomatal area could be an early mechanism to save water in this species. However, only genotype 14P11 showed further significant decrease of this trait under the highest salinity level, combined with a significant reduction in leaf length. In addition, this genotype showed the lowest leaf abscission rate at the end of salt stress period. The genotype 6K3 was severely affected by leaf necrosis and showed the highest leaf abscission rate in salt stress conditions. In the moderately tolerant genotype 2AS11, an intermediate plastic behaviour in both leaf morphology and physiology was observed during the experiment. The phenotypic variation among the three genotypes in terms of micromorphology and stomatal conductance is discussed in relation to plant functionality in salt stress conditions. Overall results suggest that leaf morphological habit contributes to salt tolerance in P. alba.     

Bacterial infection systemically suppresses stomatal density

Many plant pathogens gain entry to their host via stomata. On sensing attack, plants close these pores to restrict pathogen entry. Here, we show that plants exhibit a second longer term stomatal response to pathogens. Following infection, the subsequent development of leaves is altered via a systemic signal. This reduces the density of stomata formed, thus providing fewer entry points for pathogens on new leaves. Arabidopsis thaliana leaves produced after infection by a bacterial pathogen that infects through the stomata (Pseudomonas syringae) developed larger epidermal pavement cells and stomata and consequently had up to 20% reductions in stomatal density. The bacterial peptide flg22 or the phytohormone salicylic acid induced similar systemic reductions in stomatal density suggesting that they might mediate this effect. In addition, flagellin receptors, salicylic acid accumulation, and the lipid transfer protein AZI1 were all required for this developmental response. Furthermore, manipulation of stomatal density affected the level of bacterial colonization, and plants with reduced stomatal density showed slower disease progression. We propose that following infection, development of new leaves is altered by a signalling pathway with some commonalities to systemic acquired resistance. This acts to reduce the potential for future infection by providing fewer stomatal openings.     

弱光下生长的葡萄叶片蒸腾速率和气孔结构的变化

 植物能够对生长环境产生生态适应性,这种适应性可从气孔导度、光合速率、水分利用效率等生态指标上反映出来。为了研究葡萄蒸腾特性对弱光环境的适应性变化,本试验以‘京玉’葡萄幼苗（Vitis vinefera cv. Jingyu）为试验材料,通过遮光处理（2个处理,分别遮光65%和85%）营造弱光环境,测定了在弱光环境下生长的葡萄叶片蒸腾速率、气孔导度、水分利用效率对光照强度的响应,同时用扫描电镜技术观察了气孔的发育。结果表明,弱光环境下生长的葡萄幼苗,叶片的水势较高,但水分利用效率较低,叶片蒸腾速率和气孔导度变化对光照强度的响应缓慢,而自然光下生长的葡萄叶片则反应较迅速。通过对气孔结构的研究发现,与自然光照环境下生长的植株相比,在弱光环境下生长的葡萄幼苗,叶片下表皮的气孔横轴变宽,大小气孔之间差异减少,气孔外突,表皮细胞变大甚至扭曲,角质层变薄。说明葡萄幼苗能够对弱光环境产生适应性变化,其蒸腾特性的变化与其气孔结构的变化相关,具有一致性。     

27种木犀属植物叶表皮微形态特征的研究

利用光学显微镜和扫描电子显微镜观察了27种木犀属植物的叶表皮,测量并统计了气孔器类型、气孔大小、气孔密度、气孔指数及腺点密度等指标,以明确各种的叶表皮细胞形状及垂周壁式样、表皮角质膜、蜡质纹饰及气孔外拱盖的具体特征。结果显示:木犀属植物叶下表皮有气孔器,形状为圆形、椭圆形;气孔器类型多为不规则型,只有总状桂花和狭叶木犀为环列型;气孔器外围角质层有放射状、条状、环状、颗粒状等多种类型;叶表皮细胞形状有无规则形和多边形2种;下表皮腺点的数目远远大于上表皮。研究表明,木犀属植物气孔器和叶表皮细胞特征在种之间差异比较明显,可以作为种间鉴定的重要依据,具有重要的分类学意义。     

Effects of turgor potentials of epidermal cells neighbouring guard cells on stomatal opening in detached leaf epidermis and intact leaflets of Vicia faba L. (faba bean)

Leaflets of Vicia faba L. (faba bean) were used to determine whether the mechanical forces resulting from the turgor potentials (Φ_p) of the larger epidermal cells neighbouring guard cells play a significant role in regulating stomatal aperture. When Φ_p, of epidermis and Φ_p of bulk leaflet tissue were compared at midday, Φ_p of epidermis were only 15–25% those of bulk leaflet tissue at all but the most negative leaflet water potentials (Φ). When plants were bagged to increase Φ by reducing vapour pressure differences between leaflets and air, Φ_p of bulk leaflet tissue increased to predawn values, but Φ_p, of epidermis increased to only = 20% of predawn values and stomata opened to their widest apertures. Stomatal apertures were positively correlated with Φ_p of bulk leaflet tissue but they were not correlated with Φ_p of epidermis. Reductions in epidermal Φ_p, began predawn, before stomata were open, and reached minimum values at midday, when stomata were open. We conclude that, in Vicia faba, (1) reduction of Φ_p of epidermal cells begins predawn, reducing the counterforce to stomatal opening that would exist if full epidermal turgor were maintained throughout the day, and (2) changes in Φ_p, of leaf epidermal cells do not play a significant role in regulating stomatal aperture.     

Relationships between gas-exchange characteristics and stomatal structural modifications in some desert grasses under high salinity

Two populations, one from lesser saline Derawar Fort (DF) and the other from highly saline Ladam Sir (LS) in the Cholistan desert, for each of the five grass species, Aeluropus lagopoides, Cymbopogon jwarancusa, Lasiurus scindicus, Ochthochloa compressa, and Sporobolus ioclados were examined to investigate the influence of salinity on structural and functional characteristics of stomata. Salinity tolerance in A. lagopoides mainly depended on controlled transpiration rate (E) and high water-use efficiency (WUE), which was found to be regulated by fewer and smaller stomata on both leaf surfaces as well as stomatal encryption by epidermal invaginations. C. jwarancusa had sunken stomata on the abaxial surface only, which largely reflected a reduced E, but less affected stomatal conductance (g _s) or WUE. L. scindicus had fewer but larger stomata along with hairs/trichomes which may function to avoid water loss through transpiration, and hence, to attain a high WUE. In O. compressa stomata were found only on the abaxial surface and these were completely encrypted by epidermal invaginations as well as a dense covering of microhairs, which was associated with a low E and high WUE under salinity stress. In S. ioclados, the traits of increased stomatal density and decreased stomatal area may be critical for stomatal regulation under salt-prone environments. High stomatal regulation depended largely on stomatal density, area, and degree of encryption under salinity, which is of great ecophysiological significance for plants growing under osmotic stresses.     

新疆14种青兰属植物叶表皮微形态结构研究

应用光学显微镜和扫描电镜,对新疆14种青兰属(DracocephalumL.)植物叶片的微形态特征进行观察,结果表明:该属植物只有宽齿青兰(Dracocephalum paulsenii Briq.)叶的下表皮细胞为多边形,其余种植物叶的上、下表皮均为不规则形;垂周壁式样有深波状、波状、浅波状、平直-弓形;气孔器均为横列型;气孔形状有椭圆形、长椭圆形、宽椭圆形、近圆形;表皮毛的类型为小刺毛、短柔毛、长柔毛、头状腺毛和盾状腺毛。在不同种间甚至是同种植物叶的上、下表皮上,气孔器的大小、气孔密度、气孔指数、气孔外拱盖内缘、表皮毛、角质层纹饰等的微形态特征都存在很大的差异,可为探讨本属种间的分类、亲缘关系和演化趋势提供理论依据。     

新疆委陵菜属不同花柱组植物叶表皮微形态结构的研究

利用光学显微镜和扫描电子显微镜,观察了新疆委陵菜属5组不同花柱组10种4变种植物叶表皮的微形态特征,测量统计叶表皮毛的类型、表皮细胞的形状及大小、气孔器的分布及类型、气孔的形状、大小、密度及指数、气孔外拱盖形态及其纹饰等指标。结果显示:新疆委陵菜属10种4变种植物叶的下表皮均有气孔器的分布,形状为长椭圆形、椭圆形、宽椭圆形和近圆形;气孔器的类型多为无规则四细胞型、无规则型、围绕型和辐射型;表皮毛的类型为针状毛、带状柔毛和腺毛;表皮细胞的形状分为不规则形和多边形2种类型。研究表明,新疆委陵菜属植物表皮毛特征、叶片表皮细胞的形状、垂周壁式样、气孔器的形状类型、气孔密度指数及外围蜡质纹饰等存在差异,对属以下等级的划分有重要价值,可作为物种分类及鉴别的依据,同时也为本属一些分类群间的系统关系的探讨提供佐证。     

Biochemical studies of Aloe vera (Aloe barbadensis Miller) gel of the field grown and micropropagated plants at different developmental stages

The biochemical composition of leaf gel isolated from vegetative and micropropagated Aloe vera plants at different stages of development had been compared. The total sugars, fructose, sucrose and starch were higher in micropropagated leaf gel at all developmental stages. The micropropagated plants have higher α-amylase activity at all stages with maximum at 6 month old. Catalase and peroxidase activities were higher in younger leaves (up to 4 month old) in both types of plants. The calcium and magnesium level increases up to maturity and ranges from 0.19 to 1.12% and 0.02 to 0.10% respectively, in conventionally grown plants whereas it was a little higher in micropropagated plants. Micropropagated plants had 12.5% higher phosphorus levels. The micropropagated plants (1 month old) have 60% higher phenol content as compared to conventional plants. The micropropagated mature plants have 55 and 18.6% higher saponin and sterol contents as compared to conventional plants. The composition of aloe vera gel depends upon the growth stages and method of propagation.     

15种蹄盖蕨科植物叶表皮形态特征的研究

利用光学显微镜对蹄盖蕨科15种植物的叶表皮形态特征进行观察和研究。结果表明:蹄盖蕨科15种植物的上、下表皮细胞均为无规则型,垂周壁为凹凸状或深波状;上表皮细胞长宽比在1.0~3.2之间,下表皮细胞长宽比在1.0~2.6之间;在这15种植物中共观察到6种气孔器类型,即极细胞型、腋下细胞型、聚合极细胞型、聚腋下细胞型、无规则四细胞型和无规则型,每种植物具有3~4种气孔器类型,气孔均为下生型,多呈椭圆形。气孔的长宽比在1.3~2.1之间;气孔密度在32~90个/mm2之间;气孔指数为17.7%~40.9%。依据上述叶表皮形态特征将15种蹄盖蕨科植物分为3类,即双盖蕨类、蹄盖蕨类和对囊蕨类。该研究在一定程度上支持Christenhusz分类系统对蹄盖蕨科的划分,为蹄盖蕨科植物的系统分类及演化研究提供基础资料。     

Assessment of leaf micromorphology after full desiccation of resurrection plants

Resurrection plants are unique among higher plants because of their ability to withstand long periods of dehydration without damages. In this study, leaf epidermis and palisade mesophyll of three resurrection species, Haberlea rodopensis, Ramonda serbica and Ramonda myconi, grown under full desiccation and benign conditions, were analyzed by differential interference contrast microscopy. Detailed investigation of adaxial and abaxial leaf surfaces revealed species-specific differences in the size and number of epidermal cells and stomatal density. The applied full desiccation did not cause any significant deviations of these parameters from the controls. There were no changes in the size and number of mesophyll cells as well. Analysis of stomatal patterning displayed essentially hypostomatic leaves, having stomata mainly abaxially positioned. The most significant change detected in the leaves of dehydration-treated plants was the increased formation of adaxially positioned trichomes. This increase was very high in R. myconi, where the adaxial leaf surface was fully covered by trichomes. Despite the existence of small species-specific differences, the results showed uniform desiccation-related responses of the studied resurrection species. The quantified leaf epidermal and mesophyll features are discussed with respect to their possible contribution to the desiccation tolerance of resurrection species.     

Effect of ectomycorrhizal fungi on survival and growth of micropropagated plants and seedlings of Castanea sativa mill.

 Four ectomycorrhizal fungi (Amanita muscaria, Laccaria laccata, Piloderma croceum and Pisolithus tinctorius) were used to produce mycorrhiza on seedlings and micropropagated plants of Castanea sativa in vitro. Pisolithus tinctorius was most effective in colonizing roots of both micropropagated plants and seedlings. A. muscaria and L. laccata only colonized a few feeder roots of some plants and Piloderma croceum did not form mycorrhizas. Mycorrhization of micropropagated plants increased survival and growth during weaning. Accepted: 27 February 1996     

Ectopic expression of a tobacco vacuolar invertase inhibitor in guard cells confers drought tolerance in Arabidopsis

There are several hypotheses that explain stomatal behavior. These include the concept of osmoregulation mediated by potassium and its counterions malate and chlorine and the more recent starch–sugar hypothesis. We have previously reported that the activity of the sucrose cleavage enzyme, vacuolar invertase (VIN), is significantly higher in guard cells than in other leaf epidermal cells and its activity is correlated with stomatal aperture. Here, we examined whether VIN indeed controls stomatal movement under normal and drought conditions by transforming Arabidopsis with a tobacco vacuolar invertase inhibitor homolog (Nt-inhh) under the control of an abscisic acid-sensitive and guard cell-specific promoter (AtRab18). The data obtained showed that guard cells of transgenic Arabidopsis plants had lower VIN activity, stomatal aperture and conductance than that of wild-type plants. Moreover, the transgenic plants also displayed higher drought tolerance than wild-type plants. The data indicate that VIN is a promising target for manipulating stomatal function to increase drought tolerance.