强化仙桃红的研究

强化仙桃红是以成熟的仙人掌[Opuntia dillenii(Ker-Gawl)Haw.]果实为原料,用乙醇溶液浸提而获得的一种水溶性天然食用红色素,再添加保色剂强化而成。该色素在pH3—8的介质中呈艳丽的紫红色,经初步毒性试验,证明安全无毒。     

Programmed cell death promotes male sterility in the functional dioecious Opuntia stenopetala (Cactaceae)

Background and Aims

The sexual separation in dioecious species has interested biologists for decades; however, the cellular mechanism leading to unisexuality has been poorly understood. In this study, the cellular changes that lead to male sterility in the functionally dioecious cactus, Opuntia stenopetala, are described.

Methods

The spatial and temporal patterns of programmed cell death (PCD) were determined in the anthers of male and female flowers using scanning electron microscopy analysis and histological observations, focusing attention on the transition from bisexual to unisexual development. In addition, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling assays were used as an indicator of DNA fragmentation to corroborate PCD.

Key results

PCD was detected in anthers of both female and male flowers, but their patterns differed in time and space. Functionally male individuals developed viable pollen, and normal development involved PCD on each layer of the anther wall, which occurred progressively from the inner (tapetum) to the outer layer (epidermis). Conversely, functional female individuals aborted anthers by premature and displaced PCD. In anthers of female flowers, the first signs of PCD, such as a nucleus with irregular shape, fragmented and condensed chromatin, high vacuolization and condensed cytoplasm, occurred at the microspore mother cell stage. Later these features were observed simultaneously in all anther wall layers, connective tissue and filament. Neither pollen formation nor anther dehiscence was detected in female flowers of O. stenopetala due to total anther disruption.

Conclusions

Temporal and spatial changes in the patterns of PCD are responsible for male sterility of female flowers in O. stenopetala. Male fertility requires the co-ordination of different events, which, when altered, can lead to male sterility and to functionally unisexual individuals. PCD could be a widespread mechanism in the determination of functionally dioecious species.     

Soil O2 and CO2 effects on root respiration of cacti

Through use of a recently developed technique that can measure CO₂ exchange by individual attached roots, the influences of soil O₂ and CO₂ concentrations on root respiration were determined for two species of shallow-rooted cacti that typically occur in porous, well-drained soils. Although soil O₂ concentrations in the rooting zone in the field were indistinguishable from that in the ambient air (21% by volume), the CO₂ concentrations 10 cm below the soil surface averaged 540 μLL⁻¹ for the barrel cactusFerocactus acanthodes under dry conditions and 2400 μLL⁻¹ under wet conditions in a loamy sand. For the widely cultivated platyopuntiaOpuntia ficus-indica in a sandy clay loam, the CO₂ concentration at 10 cm averaged 1080 μLL⁻¹ under dry conditions and 4170 μLL⁻¹ under wet conditions. For both species, the respiration rate in the laboratory was zero at 0% O₂ and increased to its maximum value at 5% O₂ for rain roots (roots induced by watering) and 16% O₂ for established roots. Established roots ofO. ficus-indica were slightly more tolerant of elevated CO₂ than were those ofF. acanthodes, 5000 μLL⁻¹ inhibiting respiration by 35% and 46%, respectively. For both species, root respiration was reduced to zero at 20,000 μLL⁻¹ (2%) CO₂. In contrast to the reversible effects of 0% O₂, inhibition by 2% CO₂ was irreversible and led to the death of cortical cells in established roots in 6 h. Although the restriction of various cacti and other CAM plants to porous soils has generally been attributed to their requirement for high O₂ concentrations, the present results indicate that susceptibility of root respiration to elevated soil CO₂ concentrations may be more important.     

The xanthophyll cycle and energy dissipation in differently oriented faces of the cactus Opuntia macrorhiza

  Diurnal changes in titratable acidity, photosynthesis, energy dissipation activity, and the carotenoid composition of differently oriented cladodes of the cactus Opuntia macrorhiza were characterized during exposure to full sunlight in the field. Four cladode faces were chosen such that each was exposed to maximum photon flux densities (PFD) at different times of the day in addition to receiving different daily integrated PFDs. The sum of all carotenoids per chlorophyll was found to increase with increasing exposure to PFD, with the carotenoids of the xanthophyll cycle present in the most exposed face at more than twice the concentration found in the least exposed face. All faces exhibited large increases in xanthophyll cycle-dependent energy dissipation as the sun rose in the morning, even those receiving only minimal levels of diffuse radiation. The transient high levels of energy dissipation in those faces that did not receive direct sunlight in the morning may have been due to low temperature inhibition of photosynthesis (predawn low of 2°C). For the two faces receiving peak PFDs in the morning hours (north and east faces), the level of energy dissipation activity increased rapidly during exposure to direct sunlight in the early morning, gradually declining in the late morning under warm temperatures, and was negligible during the afternoon low light conditions. Changes in the xanthophyll cycle paralleled the changes in energy dissipation with the majority of the cycle present as violaxanthin (V) prior to sunrise, largely de-epoxidized to zeaxanthin (Z) and antheraxanthin (A) during exposure to direct sunlight, and reconverted to V during the afternoon. For the two faces receiving peak PFDs in the afternoon (south and west faces), energy dissipation activity increased dramatically during the early morning low light period, subsequently decreasing during midday as decarboxylation of malic acid proceeded maximally (providing a high concentration of CO₂ for photosynthesis), and then increased to the highest level in the late afternoon as the supply of malic acid was depleted and rates of photosynthetic electron transport declined. The xanthophyll cycle, largely present as Z and A prior to sunrise in the south and west faces, was de-epoxidized to the greatest extent in the late afternoon, followed by epoxidation back to the predawn level by sunset. In all cladode faces high levels of energy dissipation activity were accompanied by decreases in the intrinsic efficiency of photosystem II (PSII), indicative of a regulatory process that diverted the excess energy away from the reaction centers during periods of excess light. Furthermore, the overnight retention of Z and A by the south and west faces was accompanied by a sustained reduction in PSII efficiency (i.e., “photoinhibition”). We suggest that this “photoinhibition” represents the sustained engagement of nocturnally retained Z and A in the photoprotective down-regulation of PSII. Received: 8 May 1996 / Accepted: 9 September 1996     

Association between Opuntia species invasion and changes in land-cover in the Mediterranean region

In Mediterranean regions, biological invasions pose a major threat to the conservation of native species and the integrity of ecosystems. In addition, changes in land‐cover are a widespread phenomenon in Mediterranean regions, where an increase in urban areas and major changes from agricultural abandonment to shrub encroachment and afforestation are occurring. However, the link between biological invasions and changes in land‐cover has scarcely been analyzed. We conducted a regional survey of the distribution of the two alien prickly‐pear cacti Opuntia maxima and O. stricta in Cap de Creus (Catalonia, Spain) and related patterns of invasion to spatially explicit data on land‐cover/change from 1973 to 1993 to test the hypotheses that the two Opuntia species invade areas that have experienced large land‐cover transformations. We found that Opuntia invasion is particularly high in shrublands and woodlands located near urban areas. O. maxima are over‐represented in the shrublands and O. stricta in the woodlands that were former crops. Crop coverage has dropped by 71% in this 20‐year period. This study highlights the role of past land‐cover in understanding the present distribution of plant invasions.     

仙人掌的微繁殖

成功建立了仙人掌离体快繁的实验体系 ,并且对影响微繁殖的一些因素 ,诸如激素组合、外植体的物理状态、大量元素的含量等进行了研究。结果表明 :BA对仙人掌芽增殖具明显作用 ,MS +BA 5 .0mg/L +IBA 0 .1mg/L为最适增殖培养基 ;接种方式实验表明劈接优于整棵。钙、镁离子浓度对试管苗生长没有影响 ,但影响生根数及根长 ;NAA抑制根的伸长 ,但一定浓度可促进生根。总体而言 ,最适的生根培养基为 1 /2MS。同时发现块接比单芽接具有优势。试管苗在形态上出现一些变异。实验结果对仙人掌科其它植物的快速繁殖具有参考意义     

Volatile organic compounds as signals in a plant-herbivore system: electrophysiological responses in olfactory sensilla of the moth Cactoblastis cactorum

The morphological sensillum types on the antennae of male and female Cactoblastis cactorum were visualized by scanning electron microscopy. Electrophysiological recordings were performed for the first time on single olfactory sensilla of C. cactorum. The male sensilla trichodea house a receptor cell responding to the putative pheromone component (9Z,12E)-tetradecadienyl acetate. The sensilla trichodea of the females were much shorter than those of the males and contained specialized receptor cells responding to certain terpenoids, the most frequent being the nerolidol-sensitive cell. The sensilla auricillica and sensilla basiconica of both sexes contained cells responding less specifically to terpenoid compounds as well as to green leaf volatiles. Cells of the sensilla coeloconica responded to aliphatic aldehydes and acids. Eight volatile organic compounds emitted by Opuntia stricta, a host plant of C. cactorum, were identified using gas chromatography-mass spectrometry, beta-caryophyllene being the major compound. Five compounds identified by gas chromatography in the headspace of O. stricta elicited responses in olfactory receptor cells of C. cactorum, nonanal being the most active compound and therefore a candidate attractant of C. cactorum.     

Ecological genetics of the Adh-1 locus of Drosophila buzzatii

The Adh-1 polymorphism of Drosophila buzzatii was studied in terms of the effects of the larval substrate (laboratory food and Opuntia stricta tissue inoculated with live yeast species) on larval survival, development time and subsequent adult size, using the three common Adh-1 genotypes. Studies with laboratory food yielded mixed results, but in general the Adh-1^b/Adh-1^b genotype was superior to Adh-1^c/Adh-1^c with the heterozygote intermediate. Studies with the natural substrate (Opuntia stricta tissue) using mono- and bicultures of four associated yeast species also showed that the Adh-1^b/Adh-1^b genotype develops faster and survives better than Adh-1^c/Adh-1^c. There were no genotype-by-yeast interactions which might explain the maintenance of the polymorphism. Drosophila buzzatii larvae develop faster and attain larger adult sizes when raised on bicultures of yeasts as compared with the corresponding monocultures.     

Environmental influences on the productivity of three desert succulents in the south-western United States

Abstract Net CO₂ uptake over 24 h periods for shoots of Agave deserti, Ferocactus acanthodes, and Opuntia ficus-indica was measured under the ranges of water status, air temperature, and photo-synthetically active radiation (PAR) that occur in the south-western U.S.A. An environmental productivity index (EPI) was constructed indicating the overall influence of these three factors on net CO₂ uptake. Using growth chambers whose conditions were changed monthly to simulate the environmental conditions at a field site, the observed shoot dry weight increases per unit surface area changed in concert with monthly changes in EPI. The observed dry weight gain of the shoot was 17–19% lower than the predicted shoot net CO₂ uptake, which could be accounted for by carbon diversion to the roots. Mean monthly EPI was also predicted for 21 sites in the south-western U.S.A. All three species had low EPIs in the Colorado River basin, which has low annual rainfall and high summer temperatures, and in the north-central part of the region, which has low temperatures and low PAR during winter when water is available. The two native species, A. deserti and F. acanthodes, had high EPIs beyond their range in coastal southern California, where competition by other vegetation for PAR may limit net CO₂ uptake. Such regions as well as south-central California and south-central Arizona had high EPIs for all three species, indicating that these areas would be appropriate for the cultivation of O. ficus-indica.     

Crassulacean acid metabolism (CAM) offers sustainable bioenergy production and resilience to climate change

Biomass production on low‐grade land is needed to meet future energy demands and minimize resource conflicts. This, however, requires improvements in plant water‐use efficiency (WUE) that are beyond conventional C3 and C4 dedicated bioenergy crops. Here we present the first global‐scale geographic information system (GIS)‐based productivity model of two highly water‐efficient crassulacean acid metabolism (CAM) candidates: Agave tequilana and Opuntia ficus‐indica. Features of these plants that translate to WUE advantages over C3 and C4 bioenergy crops include nocturnal stomatal opening, rapid rectifier‐like root hydraulic conductivity responses to fluctuating soil water potential and the capacity to buffer against periods of drought. Yield simulations for the year 2070 were performed under the four representative concentration pathway (RCPs) scenarios presented in the IPCC's 5th Assessment Report. Simulations on low‐grade land suggest that O. ficus‐indica alone has the capacity to meet ‘extreme’ bioenergy demand scenarios (>600 EJ yr^?1) and is highly resilient to climate change (?1%). Agave tequilana is moderately impacted (?11%). These results are significant because bioenergy demand scenarios >600 EJ yr^?1 could be met without significantly increasing conflicts with food production and contributing to deforestation. Both CAM candidates outperformed the C4 bioenergy crop, Panicum virgatum L. (switchgrass) in arid zones in the latitudinal range 30°S–30°N.