Leaf structure of the cerrado (Brazilian savanna) woody plants

With the aim of recognizing the commonest leaf pattern found in the woody flora of the cerrado (the Brazilian savanna) we analyzed the leaf anatomy of 30 representative species. The leaves are mostly dorsiventral and hypostomatic and covered by trichomes and a thick layer of wax and cuticle; the vascular bundles are surrounded by a sheath of fibers. The mesophyll has a developed palisade tissue, dispersed sclerified cells and idioblasts bearing crystals and phenolic compounds. We compared the results with those reported for other species (60 species) from the same biome and for the families that the studied species belong. The present study suggests that the xeromorphism observed for the cerrado leaves is related to the evolutionary history of this biome, since its first floristic elements must have faced deficient water conditions as well as the consequent soil acidity and toxicity. Therefore we may infer that the leaf anatomical pattern here observed was already present in the first elements of the cerrado and was selected to guarantee the survival of those species in the new environment. Furthermore, the xeromorphic features present in those leaves continue nowadays to help the plants protecting themselves from the different biotic and abiotic factors they are subjected to.     

Effects of an invasive plant on a desert sand dune landscape

Given the abundance of non-native species invading wildland habitats, managers need to employ informed triage to focus control efforts on weeds with the greatest potential for negative impacts. Our objective here was to determine the level of threat Sahara mustard, Brassica tournefortii, represents to meeting regional goals for protecting biodiversity. Sahara mustard has spread throughout much of the Mojave and lower Sonoran Deserts. It has occurred in southern California’s Coachella Valley for nearly 80 years, punctuated by years of extremely high abundance following high rainfall. In those years the mustard has clear negative impacts on the native flora. Using mustard removal experiments we identified reductions in native plant reproduction, shifting composition increasingly toward Sahara mustard while decreasing the fraction of native species. High between-year variance in precipitation may be a key to maintaining biodiversity as the mustard is less abundant in drier years. Sahara mustard impacts to the native fauna were much less evident. Of the animal species evaluated, only the Coachella Valley fringe-toed lizard, Uma inornata, demonstrated a negative response to mustard abundance; however the impacts were short-lived, lasting no more than a year after the mustard’s dominance waned. Without control measures the long-term impacts to desert biodiversity may rest on the changing climate. Wetter conditions or increased periodicity of high rainfall years will favor Sahara mustard and result in reduced biodiversity, especially of native annual plants. Drier conditions will keep the mustard from becoming dominant but may have other negative consequences on the native flora and fauna.     

Leaf structure and specific leaf mass: the alpine desert plants of the Eastern Pamirs, Tadjikistan

This study examines interrelationships between eight leaf attributes (specific leaf mass, area, dry mass, lamina thickness, mesophyll cell number per cm², mesophyll cell volume, chloroplast volume, and number of chloroplasts per mesophyll cell) in field-grown plants of 94 species from the Eastern Pamir Mountains, at elevations between 3800 and 4750 m. Unlike most other mountain areas, the Eastern Pamirs, Karakorum system, Tadjikistan provide localities where low temperatures and radiation combine with moisture stress at high altitudes. For all the attributes measured, significant differences were found between plants with different mesophyll types. Leaves with dorsiventral palisade structure (dorsal palisade, ventral spongy mesophyll cells) had thicker leaves with larger but fewer mesophyll cells, containing more and larger chloroplasts. These differences in mesophyll type are reflected in differences in the total surface of mesophyll cells per unit leaf area ( A _mes/ A ) or volume ( A _mes/ V ). Plants with isopalisade leaf structure (palisade cells under both dorsal and ventral surfaces) are more commonly xerophytes and their increased values of A _mes/ A and A _mes/ V decrease CO₂ mesophyll resistance, which is an important adaptation to drought. Path analysis shows the critical importance of mesophyll cell volume in leading to the covariance between the different leaf attributes and hence to specific leaf mass (SLM), even though mesophyll cell volume is not itself strongly correlated with SLM. This is because mesophyll cell volume increases SLM through its effects on leaf thickness and chloroplast number per cell, but decreases SLM through its negative effect on mesophyll cell density.     

科尔沁沙地农田-沙丘交错区白草无性系的生态适应性分析

对生长在不同沙地生境下的白草无性系进行了个体生长与形态以及种群生物量等指标的比较研究,结果表明,生长在不同生境下的白草无性系表现出显著的形态可塑性和不同的生物量分配模式,生长在农田-沙丘过滤带上的白草无性系与生长在半固定沙丘上的白草无性系相比,具有更大的生物量,更快的叶片延伸速率,根茎总长度和节间长度更长,不定芽更多,地下生物量所占比例更大且分布更深;这些特征的出现与农田-沙丘过渡带上土壤表层比较疏松而下层水分状况相对优越有着密切关系,因而生长在农田-沙丘过渡带上的白草无性系能更快地拓展其生存空间,在固沙和沙生植被演替中起重要作用。     

几种沙漠地区野生药用植物资源及其引种栽培

几种沙漠地区野生药用植物资源及其引种栽培尹林克（中国科学院吐鲁番沙漠植物园,新疆吐鲁番８３８００８）Ｒｅｓｏｕｒｃｅｓｏｆｓｅｖｅｒａｌｓｐｅｃｉｅｓｏｆｗｉｌｄｍｅｄｉｃｉｎａｌｐｌａｎｔｓｉｎｄｅｓｅｒｔｒｅｇｉｏｎａｎｄｔｈｅｉｒｉｎｔｒｏｄｕ...     

Micropropagation systems for the mexican redbud (Cercis canadensis var. Mexicana L.) and other woody plants of the chihuahuan desert

Summary There are many Chihuahuan desert species that have potential as landscape plants for the arid communities of the southwestern United States [agarita, Berberis trifoliata Moric.; Mexican buckeye, Ungnadia speciosa Endl.; Texas madrone, Arbutus xalapensis var. texana (Buckl.). A. Gray]. Within these plant populations, there are superior genotypes that offer even greater interest for the landscape. However, it is difficult to clonally propagate many of these species with conventional techniques, and the seed-derived populations often do not breed true. Therefore, selection of superior genotypes in wild populations coupled with clonal propagation through tissue culture may offer an attractive option. It is relatively easy to achieve disinfestation of explants from desert plants due to a general lack of natural surface contamination by fungi and bacteria, even though interference from numerous trichomes can impede good contact with disinfesting agents. However, there is only a narrow window of time that is ideal for explant collection, because of the brief, periodic flushes of growth that characterize this unusual plant group. There may be years when, due to the harsh environment, the amount of suitable explant material is severely limited. Phenolics and exudates are also problematic in this group of plants, and acclimatization of ex vitro plantlets to the harsh desert environment is a particular challenge. For these reasons, specific adaptations and modifications were necessary to achieve success with micropropagation of desert plant species such as Mexican redbud (Cercis canadensis var. mexicana L.).     

Effect of temperature on the progamic phase in high-mountain plants

Progamic processes are particularly temperature-sensitive and, in lowland plants, are usually drastically reduced below 10 °C and above 30 °C. Little is known about how effectively sexual processes of mountain plants function under the large temperature fluctuations at higher altitudes. The present study examines duration and thermal thresholds for progamic processes in six common plant species (Cerastium uniflorum, Gentianella germanica, Ranunculus alpestris, R. glacialis, Saxifraga bryoides, S. caesia) from different altitudinal zones in the European Alps. Whole plants were collected from natural sites shortly before anthesis and kept in a climate chamber until further processing. Flowers with receptive stigmas were hand-pollinated with allopollen and exposed to controlled temperatures between -2 and 40 °C. Pollen performance (adhesion to the stigma, germination, tube growth, fertilisation) was quantitatively analysed, using the aniline blue fluorescence method. Pollen adhesion was possible from -2 to 40 °C. Pollen germination and tube growth occurred from around 0 to 35 °C in most species. Fertilisation was observed from 5 to 30-32 °C (0-35 °C in G. germanica). The progamic phase was shortest in G. germanica (2 h at 30 °C, 12 h at 5 °C, 24 h at 0 °C), followed by R. glacialis (first fertilisation after 2 h at 30 °C, 18 h at 5 °C). In the remaining species, first fertilisation usually occurred after 4-6 h at 30 °C and after 24-30 h at 5 °C. Thus, mountain plants show remarkably flexible pollen performance over a wide temperature range and a short progamic phase, which may be essential for successful reproduction in the stochastic high-mountain climate.     

Responses of photosynthesis,leaf conductance and growth to different salinities in three coastal dune plants

The effects of soil-water salinity on growth and photosynthesis of three coastal dune plants were examined by salt-treatment in order to clarify the causal relationship between salinity and plant distribution in a dune habitat. Plants were cultivated hydroponically at three salinity levels: 0, 10 and 100 mM NaCl. With the 100 mM salt treatment,Calystegia soldanella (C₃ species) had the highest relative growth rate (RGR) (0.085 g g⁻¹ d⁻¹), followed byCarex kobomugi (C₃) (0.066), andIschaemum anthephoroides (C₄) (0.060). This order coincides with the distribution pattern of the three species on coastal dunes;Calystegia soldanella is generally distributed in more seaward areas whereasI. anthephoroides occurs further inland. The order of RGR was determined exclusively by leaf area ratio (LAR) among the three species. Due to its C₄ pathway,I. anthephoroides had higher net photosynthetic rate (Pn) and net assimilation rate (NAR) than the two C₃ plants at all NaCl concentrations, despite its low RGR. This apparent discrepancy is explainable by differences of LAR among the three species; LAR ofI. anthephoroides was lowest, and about half that ofCalystegia soldanella. These results suggest that LAR is one of the main determinants of salt tolerance based on RGR, whereas Pn or NAR may not be significant. This article is dedicated to Professor Hideo Iwaki, University of Tsukuba, in appreciation of the sincere encouragement he has given to the authors.     

Intermediate complex morphophysiological dormancy in seeds of the cold desert sand dune geophyte Eremurus anisopterus (Xanthorrhoeaceae; Liliaceae s.l.)

Background and Aims

Little is known about morphological (MD) or morphophysiological (MPD) dormancy in cold desert species and in particular those in Liliaceae sensu lato, an important floristic element in the cold deserts of Central Asia with underdeveloped embyos. The primary aim of this study was to determine if seeds of the cold desert liliaceous perennial ephemeral Eremurus anisopterus has MD or MPD, and, if it is MPD, then at what level.

Methods

Embryo growth and germination was monitored in seeds subjected to natural and simulated natural temperature regimes and the effects of after-ripening and GA₃ on dormancy break were tested. In addition, the temperature requirements for embryo growth and dormancy break were investigated.

Key Results

At the time of seed dispersal in summer, the embryo length:seed length (E:S) ratio was 0·73, but it increased to 0·87 before germination. Fresh seeds did not germinate during 1 month of incubation in either light or darkness over a range of temperatures. Thus, seeds have MPD, and, after >12 weeks incubation at 5/2 °C, both embryo growth and germination occurred, showing that they have a complex level of MPD. Since both after-ripening and GA₃ increase the germination percentage, seeds have intermediate complex MPD.

Conclusions

Embryos in after-ripened seeds of E. anisopterus can grow at low temperatures in late autumn, but if the soil is dry in autumn then growth is delayed until snowmelt wets the soil in early spring. The ecological advantage of embryo growth phenology is that seeds can germinate at a time (spring) when sand moisture conditions in the desert are suitable for seedling establishment.     

西方蜜蜂幼虫发育温度对成体翅膀形态的影响

为探讨不同恒定温度条件对培育蜜蜂蛹翅膀形态特征的影响,作者将进入蛹期的西方蜜蜂(Apismellifera)放入人工气候箱里,分别在32、35和36℃的恒定温度条件培育,直到蜜蜂蛹羽化出房为止。测量了蜜蜂翅膀的标准形态特征,包括翅的大小、肘脉长和11个翅肘脉角,所得到的数据进行多变量比较分析、相关性分析、主成分分析和区别分析。研究结果表明,不同温度条件对蜜蜂翅膀形态特征有明显的影响     

On a new subsection of Pandanus section Cauliflora (Pandanaceae) with paniculate staminate inflorescence structure,distinctive leaf anatomy and pollen morphology

A new subsection, Pandanus section Cauliflora subsection Paniculiflora, is described to contain P. halleorum, on the grounds of the paniculate structure of its staminate inflorescence, a feature not known elsewhere within the genus Pandanus. Both leaf anatomy and pollen morphology appear to support this taxonomic separation.     

内蒙古高原西部荒漠区锦鸡儿属(Caragana)优势种的形态适应特征

研究内蒙古高原西部荒漠区锦鸡儿属（Caragana）4种优势植物——柠条锦鸡儿、狭叶锦鸡儿、垫状锦鸡儿和荒漠锦鸡儿的地理分布和叶形态适应特征.通过地理分布和生长发育研究发现：4种锦鸡儿均能在阿拉善荒漠区分布和正常生长,它们能够适应阿拉善荒漠区环境.叶形态结构研究表明：狭叶锦鸡儿叶片呈瓦状,在一定程度上阻碍了水分散失和气体交换,缩小受光面积;垫状锦鸡儿叶片卷成筒状,水分散失和气体交换阻力更大,受光面积更小.柠条锦鸡儿密被伏帖绢毛、狭叶锦鸡儿多被灰白色柔毛、垫状锦鸡儿密被绢毛和荒漠锦鸡儿密被直立绢毛,对光线反射能力强,使叶温降低,减少蒸腾.狭叶锦鸡儿和垫状锦鸡儿具有的长条型叶,4种荒漠区锦鸡儿都具有更小的叶面积、更大的厚度/面积比值、更低的叶片生物量和更小的比叶面积（SLA）,减小了蒸腾和受光面积,提高了荒漠区锦鸡儿的保水能力.荒漠区锦鸡儿这些叶片形态特性有利于适应干旱、高温和强辐射的荒漠区环境.叶绿素含量测定和叶色研究结果表明：4种荒漠区锦鸡儿叶绿素含量低,更低的叶绿素含量和密被灰白色柔毛或绢毛导致叶色浅、反光性能好,有利于减少对辐射的吸收,避免强辐射对植物的伤害,同时也使叶温低,减轻高温伤害和水分蒸发,以适应环境.这是荒漠区锦鸡儿适应高光强、高气温、极干旱的荒漠区环境的特性.垫状锦鸡儿和柠条锦鸡儿叶绿素a/b高也是适应强辐射的特性.比较4种荒漠区锦鸡儿的叶形态特性发现,4种荒漠区锦鸡儿植物对荒漠环境的形态适应方式是不同的.     

Temperature and leaf osmotic potential as factors in the acclimation of photosynthesis to high temperature in desert plants

Seasonal changes in the high temperature limit for photosynthesis of desert winter annuals growing under natural conditions in Death Valley, California were studied using an assay based upon chlorophyll fluorescence. All species of this group were 6 to 9°C more tolerant of high temperature at the end of the growing season (May) than at its beginning (February). Over this same time period, the mean daily maximum air temperatures increased by 12°C. Laboratory studies have demonstrated that increases in thermal tolerance could be induced by increasing growth temperature alone. For plants growing under field conditions there was also a good correlation between the thermal tolerance of leaves and the osmotic potential of leaf water, indicating that increases in the concentrations of some small molecules might also confer increased thermal tolerance. Isolated chloroplast thylakoids subjected to increasing concentrations of sorbitol could be demonstrated to have increased thermal tolerance.     

龙眼荔枝卷叶蛾类寄主植物种类的初步研究

对广西龙眼荔枝卷叶蛾类寄主植物种类的初步考查结果表明,目前所采到的卷叶蛾种类中,它们的寄主范围不尽相同。柑桔褐带卷蛾Adoxophyes cyrtosema达15科31种;柑桔长卷蛾Homona coffearia和棉褐带卷蛾A.orana的寄主分别有14科21种和13科20种;后黄卷蛾Cacoecia asiatica和柑桔黄卷蛾Archips seminubibis的寄主有10科14种和8科13种;三角新小卷蛾Olethreutes leucaspis、圆角卷蛾Ebodocellerigera和斜斑小卷蛾Andrioplecta oxystaura,目前仅发现危害龙眼及荔枝。新发现柑桔长卷蛾可危害翠蜜枣、指天椒和皱果苋,柑桔黄卷蛾危害粪箕笃、苦丁茶、指天椒,柑桔褐带卷蛾可危害黑面神(Breyniafruticosa)。     

An analysis of photosynthetic response and adaptation to temperature in higher plants: temperature acclimation in the desert evergreen Nerium oleander L*

Abstract. Factors underlying the process of photosynthetic acclimation to temperature were investigated for the shrub Nerium oleander L. Ramets of a single clone were grown under day/night temperature regimes of 20°C/15°C or 45°C/32°C. Plants grown at the lower temperature regime possessed rates of photosynthesis twice that of the high-temperature grown plants when CO₂ fixation was measured at 20°C. In contrast, the plants grown at the high-temperature regime had twice the rate of CO₂ fixation of the 20°C/l 5°C-grown plants at a measurement temperature of 45° C. It was determined that the ability to acclimate to changes in temperature regime was present in fully mature leaves. A reciprocal transfer of plants between the two growth regimes resulted in the appearance of the CO₂ fixation characteristics appropriate to the new growth temperature after 12–14d. The response of CO₂ fixation to light, temperature, and CO₂ partial pressure and the temperature responses of soluble and membrane-bound photosynthetic enzyme systems were analysed to determine which components might be responsible for the superior photosynthetic performance of the 20°C/I5°C-grown plants at 20°C, and the enhanced high-temperature stability of the 45°C/32°C plants. The measured photosynthetic capacity of the 20°C/15°C plants could not be attributed to gross morphological, stomatal, or other physical changes, or to a general increase in the concentration of components of the photosynthetic process. Only a single enzyme, Fru-P₂ phosphatase, was affected to an extent similar to that of photosynthesis. The enhanced thermal stability of the 45°C/32°C plants may be attributed primarily to an enhanced stability of the chloroplast membrane-bound enzymatic activities and the stability of the photosynthetic carbon metabolism enzymes which require lighl for activation.     

Functional morphology of Palaeozoic ostracods: phylogenetic implications

Recent discussions of ostracod systematics have focused on soft anatomy, both as seen in extant groups and as recorded by rare examples of special fossil preservation. The position of the fossil Palaeocopina and Leperditicopida, for which no substantial soft part evidence has yet been found, remains in the view of post-Palaeozoic workers uncertain, with some doubt as to whether they should be retained within the Ostracoda. The evolution of carapace bauplans (e.g. the development of brood pouches and lobal structures in palaeocopids as well as the development of adductor muscle scar patterns, calcified inner lamellae and carapace incisures in podocopines) is discussed in relation to presumed soft anatomy. It seems possible to distinguish between plesiomorphic (ancestral, simple) and apomorphic (derived, advanced) characters and consider their significance in ostracod systematics. Although the presumed ‘protostracod’ is not known, the combination of soft anatomy, carapace architecture and behaviour (feeding techniques, brood care) provide evidence of a general body plan which appeared (at the latest) during the Ordovician and continuously evolved towards the anatomy of modern ostracods. In parallel lineages, plesiomorphic forms have died out (leperditicopids and most palaeocopines as well as metacopines), while apomorphic lineages (‘drepanellid archetype’ of palaeocopines; resistant platycopines, podocopines and myodocopines) have survived all extinction events. The evidence supports the retention of the Palaeocopina (and probably the Leperditicopida) in the Ostracoda.     

Physiological correlates of the morphology of early vascular plants

RAVEN, J. A., 1984. Physiological correlates of the morphology of early vascular plants. The early evolution of vascular land plants is considered in relation to the physiological problems of life on land. The universal characteristics of vascular plants (xylem, cuticle, stomata, intercellular air spaces, long-distance symplastic transport and alternation of generations) are discussed in terms of the essential properties of a homoiohydric phototroph. Likely precursors of vascular plants, and the physico-chemical and biotic environment in which they occurred, are outlined prior to a discussion of the selective forces acting on the evolution of vascular plants in the Upper Silurian and Lower Devonian. Emphasis is placed on biochemical and structural 'pre-adaptations' which may have occurred in the precursors of vascular plants and on which natural selection could have acted with lignified xylem, stomata, etc., as the end-products. Guiding principles in the analysis include the physiology of extant plants, physico-chemical constraints, and compatibility with the fossil record. It is concluded that the likely sequence of acquisition of vascular plant characteristics was: heteromorphic alternation of generations with an erect sporophyte; cuticularization of sporophyte; evolution of xylem; occurrence of intercellular air spaces with pores in the epidermis; stomatal activity of the pores. Endodermis and phloem-type long-distance transport probably originated around stages (3)-(5).