Environmental control of cold hardiness in woody plants

The development of cold hardiness in 2 woody plant species (Acer negundo and Viburnum plicatum tomentosum) was shown to be independent of the induction of bud dormancy. Substantial hardiness levels were obtained under controlled conditions with long days and certain low temperatures—without dormancy development as a prerequisite.

Low temperatures given during the dark period with long days induced hardiness to a level not significantly different from that of short days. Giving plants continuous 10° temperatures under long days forced plants to harden as if they were under short days, even though they were not dormant.

Development of hardiness was shown to be a photoperiodic response. Increasing weeks of short days, followed by a low temperature hardening period in darkness, brought about a progressive increase in hardiness. The short day stimulus could be reversed by long days. Following 6 weeks of short days, the rate of hardening in darkness at 5° was over twice that of plants previously exposed to long days.

     

Tolerance to herbivory in woody vs. herbaceous plants

Research on plant tolerance to herbivory has been so far largely focussed on herbaceous plants partly due to the implicit assumption that woody plants are inherently lower in their compensatory potential as compared to herbs. However, tolerance to herbivory should be an important part of resistance of woody plants because their apparency to herbivory is high due to a large size and long life span, and their defence systems cannot completely exclude herbivory. Moreover, the longer life span, more complex modularity and higher sectorality of woody plants as compared to herbs imply that compensatory responses in woody plants may take several years to develop, and that consequences of herbivore damage to individual modules may profoundly differ from whole-plant responses. Therefore, short-term studies using branches or ramets as experimental units are likely to underestimate the tolerance of woody plants to herbivory. In addition, defoliation by insects (the most common type of herbivory experienced by woody plants) is less likely to release apical dominance and trigger biomass compensation than mammalian grazing on herbaceous plants. We conclude, therefore, that the seemingly different recovery potentials exhibited by woody and herbaceous plants are more likely to be the consequences of differences between the two types of plants in modular architecture, longevity and the type of herbivory they commonly experience rather than indications of inherent differences in compensatory ability. This revised version was published online in July 2006 with corrections to the Cover Date.     

Characteristics of winter hardiness in extremely hardy twigs of woody plants

Lethal intracellular freezing rarely occurs in extremely hardytwigs, such as white birch, poplar and willow, especially whenthey are prefrozen to –15 or –20?C. These prefrozentwigs survive subsequent rapid cooling in air at – 150?C,and immersion in liquid nitrogen. The winter hardiness of thesetwigs remains stable throughout winter. Negligible changes inhardiness occur with environmental temperature fluctuations.In these twigs and in most of the hardy twig cortex, water iseasily frozen out extracellularly at temperatures as high as–15 to – 30?C. Below this range the intensity ofcold and the cooling rate does not seem to cause injury to thesetwigs. The general applicability of hypotheses proposed by Russianworkers and by Weiser on hardening and injury below –30?Cis discussed. ¹Contribution No. 1199 from The Institute of Low TemperatureScience. (Received July 17, 1972; )     

鹞落坪保护区模式地植物及乡土观赏树种研究

首次详细记录了鹞落坪国家级自然保护区模式地植物及其命名过程,并介绍保护区内具有较高观赏价值的乡土木本植物186种,隶属于53科104属,其中观花树木类50种;观形树木类37种;观果树木类18种;观叶树木类15种;树桩盆景与盆花类15种;行道树类21种;垂直绿化类25种;观赏竹类5种。对观赏特性和园林用途进行了初步探讨,以期为城市绿化及相关研究与资源利用提供参考。     

Stomatal control of photosynthesis in detached leaves of woody and herbaceous plants

Photosynthesis and transpiration were assayed in leaves and needles of some woody species (Pinus sibirica Du Tour, P. sylvestris L., Larix sibirica Ledeb., Betula pendula Roth., Quercus robur L.), annual herbaceous plants (Amaranthus cruentus L. cv. Tampala, Celosia argentea L. f. cristata (L.), Gomphrena dispersa Standl., Solanum tuberosum L., Helianthus annuus L., H. tuberosus L.), and perennial herbs (Inula helenium L., Poligonum weyrichii F. Schmidt, Polymnia sonchifolia Poepp. & Endl.). A high-precision portable gas-analyzing system GFS-3000 with a climate-controlled chamber was used for measurements on leaves both before and after leaf detachment from the shoot under conditions optimal for photosynthesis: photosynthetically active radiation of 2000 μE/(m² s), 22–25°C, and a relative humidity of 65–70%. The steady-state gas exchange in illuminated leaves of all plant species examined was characterized by a directly proportional relationship between photosynthesis and transpiration (R ₂ = 0.87). This means that the temporal course of H₂O and CO₂ gas exchange in detached leaves suffices to characterize the status of stomatal control of photosynthesis. The general trend in the effect of leaf detachment, observed in herbaceous and woody plants, is that the stomatal control of photosynthesis was retained within first 3–5 min after leaf excision. By contrast, the increase in transpiration after leaf detachment was species-specific. Because of this circumstance, the measurements of transpiration by rapid weighing method may result in overestimation of transpiration rates by 10–15% for some plant species, compared to steady-state rates of gas exchange in undetached leaves.     

Engineering salt tolerance in plants

Recent progress has been made in the identification and characterization of the mechanisms that allow plants to tolerate high salt concentrations. The understanding of metabolic fluxes and the main constraints for the production of compatible solutes (i.e. feedback inhibition and the limitation of substrate supply) open up the possibility of genetically engineering entire pathways that could lead to the production of osmoprotectants. This, together with the identification of the different sodium transporters (in particular vacuolar and plasma membrane Na(+)/H(+) antiporters) that could provide the needed ion homeostasis during salt stress, opens the possibility of engineering crop plants with improved salt tolerance.     

Elevated CO2 and the mineral content of herbaceous and woody plants

The CO₂ enrichment effects (300–650 µmol mol^-1) on mineral concentration (N, P, K, Ca, Mg, Mn, Fe, Zn), absolute total mineral contents per individual and of whole stands of four herbaceous (Trifolium repens L.,Trifolium pratense L.,Lolium perenne L.,Festuca pratensis HUDS.) and two woody species (Acer pseudo-platanus L.,Fagus sylvatica L.) were investigated.In general, the mineral concentration of the plant tissues decreased (all six species: N>Ca>K>Mg) with the exception of P. Mn and Fe were only determined for the tree species. Both decreased in concentration (Mn>Fe). Zn was only analysed forTrifolium pratense andFestuca pratensis and decreased significantly in the grass.Despite of decreases in concentrations of as much as 20% in some cases there were increases in absolute amounts per individual and, therefore, in the whole vegetation up to 25% because of the enhanced dry matter accumulation at elevated CO₂ supply.Dedicated to Prof. Dr. R. Bornkamm, TU-Berlin, on behalf of his 60th birthday     

A simple and sensitive high-throughput GFP screening in woody and herbaceous plants

Green fluorescent protein (GFP) has been used widely as a powerful bioluminescent reporter, but its visualization by existing methods in tissues or whole plants and its utilization for high-throughput screening remains challenging in many species. Here, we report a fluorescence image analyzer-based method for GFP detection and its utility for high-throughput screening of transformed plants. Of three detection methods tested, the Typhoon fluorescence scanner was able to detect GFP fluorescence in all Arabidopsis thaliana tissues and apple leaves, while regular fluorescence microscopy detected it only in Arabidopsis flowers and siliques but barely in the leaves of either Arabidopsis or apple. The hand-held UV illumination method failed in all tissues of both species. Additionally, the Typhoon imager was able to detect GFP fluorescence in both green and non-green tissues of Arabidopsis seedlings as well as in imbibed seeds, qualifying it as a high-throughput screening tool, which was further demonstrated by screening the seedlings of primary transformed T₀ seeds. Of the 30,000 germinating Arabidopsis seedlings screened, at least 69 GFP-positive lines were identified, accounting for an approximately 0.23% transformation efficiency. About 14,000 seedlings grown in 16 Petri plates could be screened within an hour, making the screening process significantly more efficient and robust than any other existing high-throughput screening method for transgenic plants.     

Species-specific effects of woody litter on seedling emergence and growth of herbaceous plants

The effect of litter on seedling establishment can influence species richness in plant communities. The effect of litter depends on amount, and also on litter type, but relatively little is known about the species-specific effects of litter. We conducted a factorial greenhouse experiment to examine the effect of litter type, using two woody species that commonly co-occur in boreonemoral forest--evergreen spruce (Picea abies), deciduous hazel (Corylus avellana), and a mixture of the two species--and litter amount--shallow (4 mm), deep (12 mm) and leachate--on seedling emergence and biomass of three understorey species. The effect of litter amount on seedling emergence was highly dependent on litter type; while spruce needle litter had a significant negative effect that increased with depth, seedling emergence in the presence of hazel broadleaf litter did not differ from control pots containing no litter. Mixed litter of both species also had a negative effect on seedling emergence that was intermediate compared to the single-species treatments. Spruce litter had a marginally positive (shallow) or neutral effect (deep) on seedling biomass, while hazel and mixed litter treatments had significant positive effects on biomass that increased with depth. We found non-additive effects of litter mixtures on seedling biomass indicating that high quality hazel litter can reduce the negative effects of spruce. Hazel litter does not inhibit seedling emergence; it increases seedling growth, and creates better conditions for seedling growth in mixtures by reducing the suppressive effect of spruce litter, having a positive effect on understorey species richness.     

The F-box gene family is expanded in herbaceous annual plants relative to woody perennial plants

F-box proteins are generally responsible for substrate recognition in the Skp1-Cullin-F-box complexes that are involved in protein degradation via the ubiquitin-26S proteasome pathway. In plants, F-box genes influence a variety of biological processes, such as leaf senescence, branching, self-incompatibility, and responses to biotic and abiotic stresses. The number of F-box genes in Populus (Populus trichocarpa; approximately 320) is less than half that found in Arabidopsis (Arabidopsis thaliana; approximately 660) or Oryza (Oryza sativa; approximately 680), even though the total number of genes in Populus is equivalent to that in Oryza and 1.5 times that in Arabidopsis. We performed comparative genomics analysis between the woody perennial plant Populus and the herbaceous annual plants Arabidopsis and Oryza in order to explicate the functional implications of this large gene family. Our analyses reveal interspecific differences in genomic distribution, orthologous relationship, intron evolution, protein domain structure, and gene expression. The set of F-box genes shared by these species appear to be involved in core biological processes essential for plant growth and development; lineage-specific differences primarily occurred because of an expansion of the F-box genes via tandem duplications in Arabidopsis and Oryza. The number of F-box genes in the newly sequenced woody species Vitis (Vitis vinifera; 156) and Carica (Carica papaya; 139) is similar to that in Populus, supporting the hypothesis that the F-box gene family is expanded in herbaceous annual plants relative to woody perennial plants. This study provides insights into the relationship between the structure and composition of the F-box gene family in herbaceous and woody species and their associated developmental and physiological features.     

NaCl-induced changes in protoplasmic characteristics of Hordeum vulgare cultivars differing in salt tolerance

Water permeability and cytoplasmic viscosity and streaming were investigated in seedlings of two Hordeum vulgare cultivars differing in salt tolerance. Six-day-old seedlings were grown for 4 additional days in Hoagland solution with and without 100 m M NaCl added.
Observations and measurements were made in subepidermal cells of the coleoptile using plasmolytic and centrifugation methods and recordings of the speed of movement of microsomes.
Water permeability was about the same in controls of both cultivars, and was decreased by NaCl stress, but decreased less in the tolerant cultivar. Cells from control plants of the stress tolerant variety had a higher cytoplasmic viscosity than cells from the moderately sensitive cultivar. Cytoplasmic viscosity in both cultivars decreased due to NaCl stress, and more so in the sensitive one. Cytoplasmic streaming was faster in the controls of the salt sensitive cultivar than in controls of the salt tolerant cultivar; NaCl had no significant effect on cytoplasmic streaming in both cultivars.
The specific responses of the cytoplasm of the sensitive and tolerant cultivars to the salt treatment reflect differences in its structure and composition. These differences in the cytoplasm already exist before exposure to salt stress but some alterations of cytoplasmic parameters (e.g. water permeability) were induced by the saline environment.     

Salt uptake and salt tolerance by sunflower

Summary A normally grown crop of sunflower on red sandy loam soils was found to remove considerable quantities of chloride and sodium. On heavy clay soils with saline patches sunflower plants removed large quantities of sodium followed by chloride and sulphate. In view of its salt tolerance, it is suggested that intercropping or rotation with sunflower might help reduce soil salinity and improve soil conditions where salinity problems are coming up especially in heavy clay soils with low permeability. re]19720711     

Arbuscular mycorrhiza and salt tolerance of plants

Although salt has detrimental effects on spore germination of arbuscular mycorrhizal fungi (AMF), their hyphal growth and the colonization rate of plants under laboratory conditions, many salt tolerant plants (the halophytes) are strongly colonized by AMF in their natural habitats. AMF spores in several saline soils consist of to up to 80 % of one single species, Glomus geosporum. In contrast, roots of halophytes are mostly colonized by fungi of the Glomus intraradices group, of which many are as yet uncultured. Salt stress is intimately related to drought in saline habitats. Molecular analyses of genes expressed upon salt stress indicate that aquaporins which facilitate the transfer of water across membranes play a major role in alleviating salt stress in plants. In AMF, genes serving to scavenge reactive oxygen species (ROS) are expressed upon exposure to salt, indicating that fungi have to develop an enhanced oxidative defence. The development of AMF inocula that confer sustained salt tolerance to plants would have enormous practical applications. Many positive reports on salt stress alleviation by AMF exist. However, the state of the art has not yet reached field applications. In contrast to other recent reviews, the present article focuses on ecological aspects of the symbiosis between AMF and halophytes. It also emphasizes the complexity of the interactions between salt and drought stress as well as the role of AMF in alleviating salt stress.     

Sodium transport and salt tolerance in plants

The ability of plant cells to maintain low cytosolic sodium concentrations is an essential process associated with the ability of plants to grow in high salt concentrations. Recent results have identified pathways for Na(+) entry, and the cloning of vacuolar Na(+)/H(+) antiporters has demonstrated the role of intracellular Na(+) compartmentation in plant salt tolerance.     

外源性糖对四种木本观赏植物花粉离体培养的影响

分别以单、双、多糖作用于紫荆、紫丁香、桃、连翘四种木本观赏植物花粉的离体培养,检测其对花粉萌发、花粉管生长及花粉管胼胝体形成的影响,结果表明糖的类型和浓度对花粉萌发有较大影响,同时不同植物的花粉对糖的敏感性也存在差异;花粉管长度明显受蔗糖浓度的影响,尤其是连翘的花粉管长度,与蔗糖浓度成反比;在四种植物的花粉管生长中后期,均观察到胼胝体的形成,胼胝体形成的数量与蔗糖浓度及花粉管长度存在一定的联系;在花粉管中胼胝体的形成没有特定位点。     

植物耐盐的分子生物学基础

植物分子水平的耐盐研究是近年的研究热点,通过综述与耐盐有关的几种重要分子的性质和作用,总结了几种与植物耐盐有关的基因以及它们在盐分胁迫下的表达和调控。     

Effects of climatic warming on cold hardiness of some northern woody plants assessed from simulation experiments

Effects of climatic warming on cold hardiness were investigated for some northern woody plants. In the first experiment, seedlings of Norway spruce ( Picea abies [L.] Karst.), Scots pine ( Pinus sylvestris L.) and lodgepole pine ( Pinus contorta Dougl. var. latifolia Engelm.) were exposed to naturally fluctuating temperatures averaging −6°C (ambient) and 0°C (elevated) for 16 weeks in midwinter before they were thawed and re-saturated with water. In lodgepole pine, needle sugar concentrations had decreased by 15%, and the temperature needed to induce 10% injury to needles in terms of electrolyte leakage had increased by 6°C following treatment to elevated as compared with control temperatures. In contrast, Norway spruce and Scots pine showed no effects. The lack of an effect for Scots pine was ascribed to seedlings containing unusually large energy reserves that buffered respiratory expenditure of sugars. A strong, linear relationship between levels of cold hardiness, assessed by the electrolyte leakage method, and sugars was found when combining data from this and previous, similar experiments. In the second experiment, the evergreen dwarf shrub Empetrum hermaphroditum Hagerup was analysed for leaf cold hardiness, using the electrolyte leakage method, and sugar concentrations in late spring and late autumn during the third year of a warming experiment in a subarctic dwarf shrub community. The objective was to test the hypothesis that warming in the growing season alters hardening/dehardening cycles by increasing soil nitrogen mineralization and plant growth. Data found, however, suggested that cold hardening/dehardening cycles were unaffected by warming.