Salt tolerance of prickly pear cactus (Opuntia ficus-indica)

In view of the need to exploit saline water resources in agriculture in arid zones, we investigated the salt tolerance of Opuntia ficus-indica in plants growing in solution culture. Salt (NaCl) was added in concentrations ranging from 5 (control) to 200 mol m^-3. Cladode growth was sensitive to salinity, being 60% of the control at 50 mol m^-3 NaCl. The root-to-stem ratio decreased significantly only at 200 mol m^-3. Various other parameters were studied, such as water content, Na, K and Cl content, osmotic pressure, and CO₂ uptake. Of these parameters the decreases in cladode water content and CO₂ uptake were related to the decrease in cladode growth. Raised salinity increased cladode osmotic pressure, which was associated with tissue dehydration. We concluded that osmotic adjustment does not occur in prickly pear under salt stress.     

Isolation and characterization of polymorphic microsatellite markers in Galapagos prickly pear (Opuntia) cactus species

The Opuntia (prickly pear) genus contains over 200 species. Six of them are endemic to the Galapagos archipelago. Although these cacti are ‘keystone’ species of the Galapagos’ semi‐arid ecosystem, they have never been studied in detail. Because of their current threatened status and their important role in the ecosystem, we developed 16 microsatellite markers to study the population genetic structure of some of these species. These markers display a high level of polymorphism with numbers of alleles per locus ranging from six to 53. Results also revealed possible polyploidy in these cacti.     

Interaction of diffuse competition and insect herbivory in limiting brittle prickly pear cactus,Opuntia fragilis (Cactaceae)

We tested the effects of above- and belowground competition and evaluated insect herbivory on the growth of a common cactus (Opuntia fragilis) in Sandhills prairie. Our purpose was to determine the independent and joint contribution of these factors to the variation observed in cactus size and local abundance. We manipulated ambient prairie vegetation and surface water availability in a full factorial design. When Opuntia fragilis was released from competition with surrounding vegetation, it grew significantly larger in the second growing season, both in terms of number and size of new cladodes. Ramets grown within live prairie vegetation averaged no net growth. These ramets were also more frequently fed upon by the larvae of two internally feeding cactus insects. As a result, insect herbivory reinforced the competitive suppression of the cactus by grasses. Water supplementation had no significant effect, either on cactus growth or on insect herbivory. We conclude that the mechanism by which dense prairie vegetation influenced net growth of O. fragilis was both direct, through competition for nonwater resources such as light, and indirect, through its mediation of feeding by specialized insect herbivores. Furthermore, since the direct growth response to treatment did not precede the indirect effect of habitat-mediated variation in feeding by insects, our results contradict the current expectation that indirect effects require more time to be expressed than do direct effects.     

Self-incompatibility alleles in Polish wild pear (Pyrus pyraster (L.) Burgsd.): a preliminary analysis

Wild pear (Pyrus pyraster, syn.P. communis var.pyraster) is thought to be one of the species that gave rise to all other members of the genusPyrus, although intraspecific hybridizations with cultivated varieties could cause the disappearance of original species characteristics. S-RNase alleles from 7 different wild pear individuals, collected from various regions of Poland, were cloned on the basis of the PCR method and nucleotide sequence analyses. The hypervariable (HV) region is responsible for allele-specific S-RNase activity in the self-incompatibility mechanism. The high level of polymorphism of its sequences may constitute a source of valuable phylogenetic information. From all individuals, 14 sequences were obtained successfully, and 9 of them were novel alleles. Phylogenetic analysis of these alleles was based on the amino acid sequence interpretation of coding regions and intron nucleotide sequences. The research conducted on a limited pool of availableP. pyraster alleles gives only an initial insight into possible S-RNase allele polymorphisms in wild populations. At this stage, the results do not confirm a strong influence of cultivated pear species on the wild pear.     

The prickly pear (Opuntia ficus-indica [Cactaceae]) in South Africa: Utilization of the naturalized weed,and of the cultivated plants

In spite of successful biological control efforts, vast areas of South Africa remain infested with the spiny prickly pear weed, Opuntia ficus-indica. These remnant populations, which vary from sparse to dense and which are more or less stable, are confined mainly to the eastern Cape. They provide a popular fruit and a limited source of income for certain sectors of the population in these areas. In terms of existing legislation, there are, however, restrictions on the large-scale utilization of these fruit. A novel method for mass-rearing the cochineal insect, Dactylopius coccus, for the commercial production of a red dye (carminic acid) has been developed. The cultivated spineless prickly pear has recently been enjoying renewed attention from researchers and growers alike. Whereas it has traditionally been cultivated mainly as a droughtresistant fodder crop, and is still popular as such, it is now increasingly recognised as a fruit, in its own right, with considerable promise as a commercial crop for local and export markets. There is also a need to encourage the use of very young cladodes (nopalitos) as a highly nutritious vegetable for human consumption in South Africa.     

Preliminary analysis of drinking from seawater sources by free-ranging rhesus macaques (Macaca mulatta)

Rhesus macaques on Key Lois Island were observed drinking seawater that flowed into four holes they had excavated in the sand. Data were gathered to determine the salinity (TDS) and pH levels of the water and which animals were using the holes. Average TDS level (4,506.8 ± 1,750.8), but not pH (8.1 ± .30) level, of water from the holes differed from the surrounding seawater (TDS = 29,000, pH = 8.0). There were significant variations in TDS and pH levels of water between holes. A total of 249 drinking and 11 digging bouts were observed. Adult females drank and dug most often (46.9% of total bouts). Of the 260 total drinking and digging bouts, 76.1% (N = 198) were concentrated at one hole. This hole had the lowest average TDS level (3,714.2 ± 1,504.4) and one of the highest average pH levels (8.1 ± .29). Age/sex class differences in drinking bout frequencies may have been due to differential social status. We suggest that the holes were excavated to overcome a temporary shortage of provisioned water. © 1993 Wiley-Liss, Inc.     

A preliminary characterization of some pectins from quince fruit (Cydonia oblonga Mill.) and prickly pear (Opuntia ficus indica) peel

The preliminary characterization of a hot acid extracted pectin from quince (Cydonia oblonga Mill.) and from prickly pear (Opuntia ficus indica) peel was carried out. The yield of the extraction, the galacturonic acid content and the neutral sugar composition were determined and compared with published data on apple and lemon pectins

The pectin yield from quince was on average 0·53% on fresh weight, which is of a similar order to apple. The quince pectin had a high galacturonic content (about 78%), and a degree of methoxylation of about 59% corresponding to a medium-high methoxyl pectin.

The prickly pear pectin yield was 0·12% on fresh weight. This pectin had a galacturonic acid content of 64%, a low degree of methoxylation (10%), a high acetyl (10%) and neutral sugar content (51% galacturonic). It might be related to similar polygalacturonides present in the mucilages of other Cactaceae.     

Take it or leave it: transport of tools for future use by long-tailed macaques (Macaca fascicularis)

Future planning has previously been considered unique to humans. However, certain animals can foresee some of their future needs. We tested long-tailed macaques (Macaca fascicularis) ability to transport and after a delay use a rake, in two experiments. Firstly, six rake tool-trained macaques failed to select and after a delay, transport the rake. Secondly, five of the macaques were shaped on transporting the rake for immediate rewards. Now, all of the macaques transported and used the rake after a delay of 5 min; one was successful after 10 min and even on a few trials after 20 min. The macaques failed to plan in the first experiment, potentially because they were unable to foresee the appropriate sequence of behaviours to solve the task. After shaping, they displayed flexibility by successfully transporting tools after delays. Remarkably, several macaques generalized this behaviour by attempting to use non-provided objects or their tails. Our results show which information and experience macaques need in order to display tool transport for future use.     

Geophagy by the bonnet macaques (Macaca radiata) of southern India: A preliminary analysis

Bonnet macaques (Macaca radiata) in the Marakkanam Reserved Forest of southern India consume termitaria soils. Samples from the ingested termite mounds are compared with samples taken from the surrounding uneaten soils in an attempt to determine why the termitaria soils are eaten. Particle size, clay and primary mineral composition, geochemistry, and scanning electron microscopic analyses are used to search for a possible explanation for geophagy among the bonnet macaques. Kaolin minerals abound throughout the Marakkanam soil sample suite. But the termitaria soils are distinguished by the presence of small amounts of smectite. An abundance of kaolin minerals in combination with small amounts of smectite strongly resembles the mineralogy ofeko, a traditional African remedy for stomach ailments, and Kaopectate™, a western anti-diarrhoeal preparation. The percentage of mature leaves and fruits ofAzadirachta indica consumed by the bonnet macaques is relatively high. Plant feeding deterrents, such as, acid detergent fibre (ADF) and the inherent nature of the fruits ofAzadirachta indica, when consumed in large quantities to act as a purgative, could cause gastrointestinal upsets and diarrhoea. At Marakkanam, bonnet macaques ingest termitaria earth that would act as a pharmaceutical agent to alleviate gastrointestinal upsets and control diarrhoea.     

Preservation of fresh edible cactus stems (<i>Opuntia ficus indica</i> Mill.) by modified atmosphere packaging

Cactus stems, the cladodes of Opuntia spp. cacti, are consumed in Mexico and other countries due to their fresh and herbaceous flavor, and because of their widely known nutraceutical benefits. In order to extend the postharvest life of this vegetable, the effect of a modified atmosphere packaging (MAP) was studied in cactus stems of the cultivar Atlixco stored at 4 ± 1 °C for 20 days under three types of atmospheres: (1) air (passive atmosphere), (2) 5 kPa O₂ + 4 kPa CO₂, and (3) N₂. During storage, the titratable acidity decreased and the color of cladodes became darker and less green; however, the 5 kPa O₂ + 4 kPa CO₂ atmosphere was able to preserve both quality characteristics. All modified atmospheres reduced weight loss (from 8 to <2%) and the symptoms of chilling injury, and this physiological disorder appeared earlier in controls than in MAP-stored cladodes. The levels of fermentation metabolites were low in all three evaluated atmospheres. Because of this, only cladodes stored under the N₂ atmosphere were selected for furthersensory analysis of the MAP effect on odor perception as evaluated by a trained panel. Results indicated that there was no detrimental effect (atypical odors) of MAP on this sensory characteristic. We conclude that cultivar Atlixco is suitable for preservation using MAP technology.     

Identification by suppression subtractive hybridization of genes expressed in pear (Pyrus spp.) upon infestation with Cacopsylla pyri (Homoptera: Psyllidae)

The molecular interaction between pear tree (Pyrus spp.) and the phloem-feeding psylla Cacopsylla pyri (Linnaeus) was investigated through the construction and characterization of cDNA subtracted libraries. Genes expressed upon insect infestation were identified in the susceptible pear cultivar Bartlett and in the resistant selection NY10355. In both interactions, genes involved in the plant defense response were induced, confirming the observed similarity between the response to pathogens and to insects with piercing/sucking mouthparts. However, the two expression profiles were found to be different, with more genes involved in the response to biotic and abiotic stress being activated in the resistant plant than in the susceptible one. Further characterization of the identified genes could lead to the development of molecular markers associated with tolerance/resistance to pear psylla.     

Temperature-induced fluorescence changes : a screening method for frost tolerance of potato (solanum sp.)

Field-grown tuber-bearing potatoes were screened for frost tolerance in a late stage of development. Three different clones of Solanum tuberosum L. and two interspecific crosses between clones of S. tuberosum and the wild potato species S. demissum Lindl. were studied. Two different methods were used. (a) Temperature-induced fluorescence changes of intact leaves were measured in freeze-thaw cycles between 20°C and −10°C. The variable fluorescence pattern was characterized in relation to frost tolerance. (b) Controlled freezings of plants in a climate chamber with successively increased low temperature stress, of 1 to 2 hours duration during the dark period. Freezing damages were classified visually.     

Stratification and intra- and inter-specific differences in fatty acid composition of common dolphin (Delphinus sp.) blubber: implications for dietary analysis

Sixty-five fatty acids were quantified in the blubber of common dolphins (Delphinus delphis, D. capensis) incidentally caught off the coast of southern California. Dolphins were grouped by sex, reproductive status and species, and a blubber sample was collected at a mid-lateral site located caudal to the trailing edge of the dorsal fin. Samples were divided horizontally into inner, middle and outer layers and gradients in fatty acid content (mass percent) were observed across the depth of the blubber. Levels of monounsaturated fatty acids were greatest in the outer layer, whereas levels of saturated and polyunsaturated fatty acids were greatest in the inner layer. Degree of stratification was greatest in sexually mature dolphins. Blubber of sexually immature, but physically mature, male dolphins was also highly stratified, suggesting that this difference may be attributed to differences in diet. Classification and regression tree analysis resulted in the fewest misclassifications when dolphins were grouped by species, possibly indicating that these closely related animals forage on different prey species. Dietary-derived fatty acids were typically selected as splitting criteria in classification and regression tree analyses, suggesting that the observed differences in fatty acid composition between the various groups of dolphins may be attributed to differences in diet.     

An analysis of the role of actin during pollen activation leading to germination in pear (Pyrus communis L.): treatment with cytochalasin D

Summary Major stages of actin organization during activation leading to germination of pear (Pyrus communis L.) pollen were disrupted by treatment with 5 g/ml cytochalasin D (CD), and the effects of the drug were monitored with rhodamine-phalloidin staining. CD induced the formation of granules or short rods in the place of the filamentous arrays that occur in normally developing pollen. Filamentous arrays, however, returned upon removal of CD. Pollen incubated directly in CD showed a gradual disappearance of circular actin profiles and their replacement by either granules or, less frequently, short rods. These granules and rods initially had a random distribution in the cell, but with time in CD they became localized at one of the three germination apertures. Pollen was also allowed to reach three stages of microfilament (MF) organization (initial fibrillar arrays, interapertural MFs, and MFs confined beneath a single aperture) prior to being continously exposed to CD. After CD treatment, germination was blocked and the number of cells containing short rods increased, but movement of actin to a single aperture continued. Finally, when pollen at different stages of MF organization was treated with a CD pulse and then transferred to drug-free medium, germination was delayed regardless of the stage of MF organization at the time of treatment. The results indicate that an uninterrupted progression of actin organization is essential for pollen germination, but that movement of actin in the cell is CD-insensitive.     

Stone handling by Japanese macaques (Macaca fuscata): Implications for tool use of stone

Stone-play, a newly innovated cultural behavior, has been observed among the free-ranging Arashiyama B troop Japanese macaques near Kyoto, Japan since 1979. Conditions in which the non-purposeful handling of stones might possibly give rise to tool behavior are discussed. The progression of this behavior is traced through three phases: transmission, tradition, and transformation. During the first two phases, through social learning, the behavior was established within the group as a regular item of their behavioral repertoire and was most frequently observed after eating provisioned grain. In the third phase, observations suggest a “faddish” shift in the practice of certain behavioral sub-types between 1984 and 1985. During this period young individuals increasingly began to carry stones away from the feeding station, mixing stone manipulation with forage-feeding activities in the forest. Observations suggest under such conditions, stone handling is likely to lead to the occasional use of stone as a tool. This conclusion probably can be applied to species other thanMacaca fuscata. Consideration of the eco-setting and social learning correlates of stone handling suggests how the instrumental use of stone might emerge from a tradition of non-instrumental manipulation.     

Diademed sifakas (Propithecus diadema) use olfaction to forage for the inflorescences of subterranean parasitic plants (Balanophoraceae: Langsdorffia sp., and Cytinaceae: Cytinus sp.)

Primates usually locate food resources using visual cues and memory, yet the potential for olfactory-guided (or olfactory-assisted) food location remains relatively unexplored. Here we report observations of wild Propithecus diadema that strongly suggest that olfaction is used to locate the inflorescences of two subterranean parasitic plant species (Langsdorffia sp. and Cytinus sp.). These valued but seasonal food resources are found obscured in leaf litter, and sifakas spend considerable time on the ground engaged in what appears to be olfactory exploration before they locate the inflorescences. Because they are visually obscured and occur within a substrate that is rarely used by sifakas, accidental discovery of these resources seems unlikely. Individuals may learn to exploit them by watching conspecifics.