Ecological niche modeling and geographical distribution of pollinator and plants: A case study of Peponapis fervens (Smith, 1879) (Eucerini: Apidae) and Cucurbita species (Cucurbitaceae)

The bees of the Peponapis genus (Eucerini, Apidae) have a Neotropical distribution with the center of species diversity located in Mexico and are specialized in Cucurbita plants, which have many species of economic importance, such as squashes and pumpkins. Peponapis fervens is the only species of the genus known from southern South America. The Cucurbita species occurring in the same area as P. fervens include four domesticated species (C. ficifolia, C. maxima maxima, C. moschata and C. pepo) and one non-domesticated species (Cucurbita maxima andreana). It was suggested that C. m. andreana was the original pollen source to P. fervens, and this bee expanded its geographical range due to the domestication of Cucurbita. The potential geographical areas of these species were determined and compared using ecological niche modeling that was performed with the computational system openModeller and GARP with best subsets algorithm. The climatic variables obtained through modeling were compared using Cluster Analysis. Results show that the potential areas of domesticated species practically spread all over South America. The potential area of P. fervens includes the areas of C. m. andreana but reaches a larger area, where the domesticated species of Cucurbita also occur. The Cluster Analysis shows a high climatic similarity between P. fervens and C. m. andreana. Nevertheless, P. fervens presents the ability to occupy areas with wider ranges of climatic variables and to exploit resources provided by domesticated species.     

Calcium distribution in globoid crystals of cucurbita cotyledon protein bodies

Energy-dispersive x-ray analysis was used to investigate the location of globoid crystals with relatively high Ca levels within cotyledons of Cucurbita maxima, Cucurbita mixta, and Cucurbita andreana. The small globoid crystals in both upper and lower epidermal cells commonly contained Ca. Ca was present in globoid crystals of all provascular regions with the exception of the very small provascular regions of C. maxima. In C. maxima and C. mixta cotyledons, some cases were observed where Ca was found in the globoid crystals of the first layer of mesophyll cells surrounding the provascular region, but in general Ca was absent from globoid crystals of palisade and spongy mesophyll cells. In C. andreana, globoid crystals of palisade and spongy mesophyll cells commonly contained at least some Ca. Cell position and cell type are factors affecting the Ca content of globoid crystals in protein bodies.     

Some Effects of Potassium Deficiency on Seedling Development

Seedlings with leaf-like photosynthetic cotyledons such as Cucumissativus, Sinapis alba and Trifolium pratense have higher growthrates and a greater requirement for an external supply of potassiumthan hypogeal species (Pisum sativum, Vicia faba) or epigealspecies with very fleshy cotyledons (Phaseolus vulgaris, Lupinusalbus, Lupinus angustifolius). The initial stages of seedlingdevelopment in the latter two groups involve mainly transferof reserves from cotyledons to axis and a relatively small increasein total seedling dry weight takes place during the first 2to 3 weeks. Potassium may be drawn either from the supply already presentin the cotyledons or from an external source. Species with expandingphotosynthetic cotyledons utilize the reserve potassium duringcotyledon development and it is not transported to the epicotyl.Thus, in these species an external supply of potassium is essentialfor full development of the photosynthetic system and the roots.In species whose cotyledons are not major photosynthetic organsthe reserve potassium is transported from the cotyledons tothe developing axis. In these species culture in a nutrientsolution deficient in potassium or in distilled water increasesroot dry weight but reduces plumule weight (although to a lesserextent than in species with leaf-like cotyledons). In general,the response of seedlings to culture in a nutrient solutiondeficient in potassium was very similar to culture in distilledwater only. Thus, although all the species studied had similar levels ofpotassium in the seed (µg potassium/mg dry weight) itssite of utilization differs. It appears that seedlings withleaf-like cotyledons are more susceptible during early seedlinggrowth to deficiencies in external factors, such as potassium,than are species with fleshy cotyledons.     

Redistribution of Nutrient Elements from Cotyledons of Two Species of Annual Legumes During Germination and Seedling Growth

The distribution of dry matter and various mineral nutrientsbetween testa and embryo of seeds of Lupinus albus and L. angustifoliusis described It was found that lupin seeds at either end ofa pod contained less dry matter and minerals than seeds in themiddle of the fruit. The transport of dry matter, N, P, K, S,Ca, Mg, Na, Fe, Zn, Mn and Cu from cotyledons of parent seedsof both species to the seedling axis was measured from germinationto the time of cotyledon death. N, P, K and S were retrievedfrom cotyledons with over 90 per cent efficiency, dry matter,Mg, Na, Fe, Zn, Mn and with 59–90 per cent efficiency,and Ca with 26–31 per cent efficiency. There was littlechange in the efficiency of nutrient retrieval from cotyledonswhen seedlings were grown in different culture media. Both speciesshowed a linear relationship between the loss of each elementand dry matter throughout the experiment, and a similar proportioningbetween root and shoot of the amount of a specific nutrientmobilized from cotyledons of parent seeds. Lupinus albus L., Lupinus angustifolius L., lupin, transport, of dry matter and mineral nutrients     

Changes in Abscisic Acid Content in Axis and Cotyledons of Developing Phaseolus vulgaris Embryos and their Physiological Consequences

Prevost, I. and Le Page–Degivry, M. Th. 1985. Changesin absicisic acid content in axis and cotyledons of developingPhaseolus vulgaris embryos and their physiological consequences.—J.exp. Bot. 36: 1900–1905.Changes in abscisic acid (ABA)content with time were measured in embryonic axes and in cotyledonsof Phaseolus vulgaris embryos using a radio–immunoassay.During embryogenesis, a similar pattern was observed in bothtissues: ABA increased to a maximum 29 d after an thesis, followedby a decrease as the seed matured. The level of ABA in the cotyledonswas always much higher than that in the axes. In in vitro cultures,the duration of the lag phase before germination of isolatedembryonic axes increased with ABA content. The presence of cotyledonsalways lengthened the lag phase; longer lag phases were associatedwith greater concentrations of ABA in the cotyledons. Moreoverthe presence of cotyledons stimulated the growth of seedlings. Key words: ABA distribution, embryo maturation, axis and embryo germinability     

The Changes with Age in the Distribution of Copper and Some Copper-containing Oxidases in Red Clover (Trifolium pratense L. cv. Dorset Marlgrass): Appendix--The Determination of Nanogram Amounts of Copper in Plant Materials Using the Copper-free Apoenzyme of Pea-seedling Diamine Oxidase

Changes in activity with age of four copper-containing enzymes-ascorbateoxidase, diamine oxidase, o-diphenol oxidase, and cytochromeoxidase-were studied in red clover plants (Trifolium pratenseL. cv. Dorset Marlgrass) grown in nutrient solutions with orwithout copper. In the first 2 weeks after germination the cytochromeoxidase activities of plants grown with or without copper weresimilar, but the activities of the other three enzymes wereless in plants grown without copper. At 6 weeks the activitiesof all four enzymes were less in plants grown without copper.The copper content of the cotyledons did not change during thefirst few weeks of growth suggesting that this copper is noteasily mobilized. A new method for determining 1–10 ng amounts of Cu²⁺ isdescribed based on the specific reactivation of the copper-freeapoenzyme of pea-seedling diamine oxidase.     

Effect of Root Zone Temperature on the Mineral Composition of Xylem Sap and Plasma Membrane K+-Mg++-ATPase Activity of Grafted-Cucumber and -Figleaf Gourd Root Systems

Cucumber (Cucumis sativus L.) seedlings were grafted onto cucumber-(CG) or figleaf gourd- (FG, Cucurbita ficifolia Bouché)seedlings in order to determine the effect of solution temperature(12, 22, and 32°C) on the mineral composition of xylem sapand the plasma membrane K⁺-Mg⁺⁺-ATPase activities of the roots.Low solution temperature (12°C) lowered the concentrationof NO^–₃ and H₂PO^–₄ in xylem sap of CG plants butnot of FG plants. Concentrations of K⁺, Ca⁺⁺ and Mg⁺⁺ in xylemsap were less affected than anions by solution temperature.The plasma membrane of FG plants grown in 12°C solutiontemperature showed the highest K⁺- Mg⁺⁺-ATPase activity at allATP concentrations up to 3 mM and at low reaction temperatureup to 12°C, indicating resistance of figleaf gourd to lowroot temperature. (Received December 27, 1994; Accepted March 10, 1995)     

The recalcitrant plant species, Castanospermum australe and Trichilia dregeana, differ in their ability to produce dehydrin-related polypeptides during seed maturation and in response to ABA or water-deficit-related stresses

In constrast to seeds of orthodox species, those of recalcitrantspecies do not acquire desiccation tolerance during their developmentand are shed from the parent plant at high water contents. Dehydrinproduction in seeds of recalcitrant species was examined duringdevelopment and germination, in response to abscisic acid (ABA),and following the imposition of various water-deficit-relatedstresses, including desiccation, water stress, high salt, highosmolarity, and low temperature. Two tropical species exhibiteda differential capacity to produce dehydrin-related proteinsduring seed maturation. Dehydrins were present in axes and cotyledonsof Castanospermum australe seeds during mid-maturation and atmaturity. In Trichilia dregeana, no dehydrin-related polypeptideswere detected in the mature seed. During the development ofC. australe seeds, the nature of the dehydrin related polypeptidesaccumulated in the cotyledons and axis changed and new polypeptideswere detected in the mature seeds that were not present duringmid-maturation. The dehydrins present in cotyledons of matureseeds (31, 37 and 40 kDa) were still detectable after germination(i.e. in untreated seedlings). These dehydrins became less abundantin the cotyledons of C. australe seedlings following ABA andall stress treatments except cold, although most of the dehydrinswere still detectable. An exception was the desiccation-treatedseedlings, in which no dehydrins were detected. In the rootsof C. australe seedlings, no dehydrins were found after germinationnor were they induced in the root by ABA or any of the stresstreatments imposed on seedlings. Seedlings of Trichilia dregeanadid not produce dehydrins in the roots or cotyledons when exposedto ABA or water-deficit-related stresses. Key words: Dehydrin, ABA, desiccation, recalcitrant, seed     

Absorption and translocation of lipidic substances by plants

Young seedlings ofZea mays L. andCucurbita pepo L. were grown in water culture with a layer of oil (linum or olive oil) or liquid paraffin. The seedlings transport oil and parafin into the top and in the young root.Cucurbita seedlings proved to be very sensitive and died within few days.Zea proved to be resistant. InZea this transport of oil was found to be related to the age of the seedlings and the zone of the root in contact with oil. The oil was localised in the cell walls of different tissues of root and top, in the intercellular spaces of cortex and pith and in the xylem vessels.     

Changes in Levels of Cytokinins in Etiolated Squash Seedlings after Illumination

When etiolated seedlings of squash (Cucurbita maxima Duch. cv.Houkou-aokawaamaguri) were exposed to light, their cotyledonsbegan to accumulate chlorophyll at a low rate for the firsthour but at a high rate therafter. After 0, 1 and 2 h of illumination,cytokinin levels in cotyledons, hypocotyls and roots were analyzedby ELISA (enzyme-linked immunosorbent assay) and GC-SIM (gaschromatography-selected ion monitoring). Cytokinin levels measuredby ELISA were about 10 times higher than those measured by GC-SIM,suggesting that ELISA was not suitable for the measurementsof cytokinin levels in the extracts from these tissues. Cytokininsfound by GC-SIM were t-RZ (t-ribosyl zeatin), c-RZ, t-Z (t-zeatin),c-Z, RiP (ribosyl isopentenyladenine) and iP (isopoentenyladenine).Levels of biologically active cytokinins (t-RZ and t-Z) didnot show marked changes after illumination. Levels of c-RZ andc-Z did, however, decrease in cotyledons and increase in hypocotylsafter illumination. Promotion of the accumulation of the chlorophyllin detached squash cotyledons by exogenously applied t-Z waspartially inhibited by the addition of c-Z, suggesting thatthe decrease in the endogenous level of c-Z in cotyledons ofintact seedlings after illumination permits the light-inducedformation of chlorophyll. (Received August 8, 1990; Accepted April 4, 1991)     

Seed Storage and Germination and Seedling Proliferation in Taro, Colocasia esculenta (L) Schott

Taro seeds maintained under c. 40 per cent r.h. and 22 ±2°C retained higher viability than those stored under otherexperimental conditions. Germination was more than 60 per centon a number of defined and undefined media. Rates above 80 percent were obtained on a greenhouse potting mix or its extractor distilled water with filter paper as a support. When maintainedin the dark, seedlings cultured in vitro on one of several definedmedia etiolated and produced atypical, elongated internodeswhich resemble those of vining aroids. Plantlets which developedat their nodes were removed and raised to maturity. Colocasia esculenta (L.) Schott, taro, seed storage, seed germination, seedling proliferation     

Seed Water Relations and the Regulation of the Duration of Seed Growth in Soybean

Soybean [Glycine max (L.) Merrill] seeds and cotyledons weregrown in an in vitro culture system to investigate the relationshipsbetween cell expansion (net water uptake by the seed) and drymatter accumulation. Seeds or cotyledons grown in a completenutrient medium containing 200 mol m^–3 sucrose continueddry matter accumulation for up to 16 d after in planta seedsreached physiological maturity (maximum seed dry weight). Seedor cotyledon water content increased throughout the cultureperiod and the water concentration remained above 600 g kg^–1fresh weight. These data indicate that the cessation of seeddry matter accumulation is controlled by the physiological environmentof the seed and is not a pre-determined seed characteristic.Adding 600 mol m^–3 mannitol to the medium caused a decreasein seed water content and concentration. Seeds in this mediumstopped accumulating dry matter at a water concentration ofapproximately 550 g kg^–1. The data suggest that dry matteraccumulation by soybean seeds can continue only as long as thereis a net uptake of water to drive cell expansion. In the absenceof a net water uptake, continued dry matter accumulation causesdesiccation which triggers maturation. Key words: Glycine max (L.) Merrill, solution culture, duration of seed growth, water content, dry matter accumulation     

Cell elongation, turgor and osmotic pressure in developing sunflower hypocotyls

The relationship between cell elongation, change in turgor andcell osmotic pressure was investigated in the sub-apical regionof hypocotyls of developing sunflower seedlings (Helianthusannuus L.) that were grown in continuous white light. Cell turgorwas measured with the pressure probe. The same hypocotyl sectionswere used for determination of osmotic pressure of the tissuesap. Acceleration of cell elongation during the early phaseof growth was accompanied by a 25% decrease in both turgor andosmotic pressure. During the linear phase of growth both pressuresremained largely constant. The difference between turgor andosmotic pressure (water potential) was –0.10 to –0.13MPa. Excision of one cotyledon had no effect on growth, turgorand osmotic pressure. However, after removal of both cotyledonscell elongation ceased and a substantial decrease in both pressureswas measured. In addition, we determined the longitudinal tissuepressure in seedlings from which one or both cotyledons hadbeen removed. Tissue pressure and turgor were very similar quantitiesunder all experimental conditions. Our results demonstrate thatturgor and cell osmotic pressure show a parallel change duringdevelopment of the stem. Cessation of cell elongation afterremoval of the cotyledons is attributable to a decrease in turgor(tissue) pressure, which provides the driving force for growthin the hypocotyl of the intact plant. Key words: Cell elongation, Helianthus annuus, osmotic pressure, tissue pressure, turgor     

Effect of growth temperature on reserve mobilization and hydrolytic enzyme activities in Vigna mungo cotyledons

Seeds of Vigna mungo were allowed to germinate at 27, 18 and15°C, and time-course changes of hydrolytic enzyme activitiesand the mobilization rate of reserve components in cotyledonswere studied. The seeds germinated at 27 and 18°C grew normally,whereas the growth at 15°C was markedly retarded. In cotyledonsof seedlings grown at 27 and 18°C, amylolytic and proteolyticenzyme activities increased at early stages of growth and therates of starch and protein mobilization changed correspondingto the hydrolytic enzyme activities. At 15°C the enzymeactivities increased gradually during the experimental periodof 16 days, but the reserves in cotyledons remained almost unchangeduntil the end of the experimental period. Changes of zymogram patterns of amylolytic and proteolytic activitiesin cotyledons of seedlings grownat 27, 18 and 15°C wereexamined using polyacrylamide gel electrophoresis. The intensitiesof a main band of a-amylase and at least two bands of protease(gelatin-hydrolyzing activity) increased concurrently with invitro activities of amylolytic and proteolytic enzymes. At leastthree bands of starch phosphorylase were present in cotyledonsat early stages of germination and their intensities decreasedduring the growth of seedlings at 27, 18 and 15°C. (Received June 4, 1980; )     

Lycopene induction in Cucurbita moschata cotyledons by CPTA

2-(4-Chlorophenylthio) triethylamine hydrochloride (CPTA) inducedthe rapid accumulation of lycopene in Cucurbita moschata cotyledons.Concomitant with this increase, was a decrease in chlorophyllconcentration in green seedlings, a cessation of further plumuleand cotyledonary growth and an increase in cotyledon respiration.Light was required for maximum lycopene accumulation. (Received August 4, 1973; )     

Accumulation of Phenylpropanoids in the Cotyledons of Morning Glory (Pharbitis nil) Seedlings during the Induction of Flowering by Low Temperature Treatment, and the Effect of Precedent Exposure to High-Intensity Light

Extracts from the cotyledons of seedlings of Pharbitis nil strain‘Violet’ cultured at low temperature, which inducestheir flowering even in continuous light, with or without precedentexposure to high-intensity light, which shortens the periodof low temperature required for flowering, were analyzed byHPLC for substances correlating with the flower-inducing process.The content of two phenylpropanoids were found to increase duringthe low-temperature, and were identified as 3-O-feruloylquinicacid and dehydrodiconiferyl alcohol-13-O-ß-D-glucoside.The increase was more rapid in the cotyledons exposed to high-intensitylight before the low-temperature. This suggests that the accumulationof these compounds is correlated to the promotive effect ofhigh-intensity light on the flower-induction by low temperature. (Received March 7, 1994; Accepted April 2, 1994)     

Analysis of Lipids of Citrullus lanatus (cv. Sugar baby) During Seed Germination and Seedling Growth

Changes in the dry weight (dry wt.), total and neutral lipids,and fatty acid composition were determined in the cotyledonsand axis of Citrullus lanatus cv. Sugar baby seedlings duringtheir first 12 d growth in the dark, at 25 ? 1 ?C. The major stored reserves were mobilized between days 3 and8. The lipid concentration after day 4 decreased rapidly inthe cotyledons. On the first day the lipid concentration inthe axis was higher than in the cotyledons but decreased rapidlyand from day 5 up to the end of the experiments it remainedat very low values. In the cotyledons, the change in the fattyacid composition was relatively small compared to the significantchange observed in the axis. The neutral lipids of the cotyledonsdecreased sharply between days 2 and 6 while their fatty acidcomposition suffered no significant change. The axis, comparedto the cotyledons, contained a small but concentrated amountof neutral lipids, which decreased up to day 6. Thereafter,an increase was observed. The fatty acid composition of theaxis neutral lipids changed significantly, linoleic and oleicacid decreased while palmitic and linolenic acid increased. Key words: Citrullus lanatus, seed germination, seedling growth, lipids, fatty acids     

Requirement of cotyledons for gibberellic acid-induced hypocotyl elongation in lettuce seedlings. Isolation of the cotyledon factor active in enhancing the effect of gibberellic acid

The role of cotyledons in hypocotyl elongation caused by gibberellicacid was studied using young seedlings of lettuce, Lactuca saliva,var. ‘Grand Rapids’. Removal of cotyledons fromintact seedlings resulted in a depression of hypocotyl elongationcaused by gibberellic acid. Gibberellic acid-induced hypocotylelongation in decotylized seedlings, was however, substantiallyenhanced by incubating the seedlings together with excised cotyledons.The exudate from excised cotyledons also enhanced the effectof gibberellic acid on hypocotyl elongation in decotylized seedlings.This active principle (named the cotyledon factor) in the cotyledonexudate was stable against heating at 100?C for 15 min, permeatedthe dialysis membrane, and was extractable with ethyl acetate.Biological activity of the cotyledon factor was not replacedby indole-3-acetic acid, kinetin, cyclic AMP, vitamins, sucroseor inorganic nutrients. The biological significance of the cotyledonfactor is discussed in relation to the action of gibberellicacid. (Received February 14, 1973; )     

Flower-Inducing Activity of Water Extracts of Various Plant Species, in Particular Pharbitis nil

The crude water extracts of leaves of many plant species belongingto Spermatophyta and some belonging to Bryophyta induced floweringof Lemna paucicostata 151 (PI51) under continuous light, atthe concentrations equivalent to 0.1 to 10 mg fr wt leaf per10 ml culture medium (mg fr wt/10 ml). The extract of Salvinia(Pterydophyta) added together with the extract of Lemna at aconcentration lower than that necessary to cause flowering alsoinduced flowering. The activity of the water extracts of someplants varied considerably from experiment to experiment dueto unknown factors, but the extracts of Pharbitis nil strainViolet, a sensitive short-day plant, always showed a high activity,as did the extracts of Lemna paucicostata reported previously. The extract of Pharbitis cotyledons induced flowering of P151even at 0.3 mg fr wt/10 ml, and significantly promoted floweringof L. paucicostata 441 and 6746 at 1–3 mg fr wt/10 ml.Ex-udate from the cuttings of the seedlings was also active.However, neither the activity of the water extract nor thatof the exudate could be correlated with photoperiodic floralinduction. On the other hand, the extract of leaves or cotyledonshad higher activity (on a fr wt basis) than that of other organs,and the activity of the extract of cotyledons changed with theirage roughly in parallel with their photoperiodic sensitivity. (Received April 17, 1989; Accepted August 10, 1989)     

Effect of Sink-Source Manipulations on the Photosynthetic Rate and Carbohydrate Content of Cucumber Cotyledons

Mayoral, M. L., Plaut, Z. and Reinhold, L. 1985. Effect of sink-sourcemanipulations on the photosynthetic rate and carbohydrate contentof cucumber cotyledons.-J. exp. Bot. 36 1551–1558. The photosynthetic rate of cucumber cotyledons (Cucumis sativuscv. Dahla) reached a maximum value of 12 mg dm^–2 h^–1,10 d after emergence. In 12-d-old seedlings removal of one cotyledondoubled the CO₂ fixation rate of the other, as observed 3 dafter treatment. When the primary leaf was removed, the photosyntheticrate of the cotyledons was decreased by 33%. At this stage ofgrowth elimination of the roots as a sink for assimilates bygirdling the hypocotyl affected neither the photosynthetic ratenor the carbohydrate content of the cotyledons. By contrast,in 18-d-old seedlings removal of the first leaf brought abouta 42% increase in the photosynthetic rate of the cotyledons.The simultaneous removal of the first leaf and one cotyledondoubled the rate of CO₂ fixation of the remaining cotyledon.Girdling the hypocotyl lowered the photosynthetic rate of thecotyledons by 73%. In both 12- and 18-d-old seedlings a decreaseor increase in the sink-source ratio was correlated with anincrease or a decrease respectively in the carbohydrate contentof the cotyledons. The stomatal resistance of the cotyledonswas not affected by any of the treatments. The effect of sink-sourcemanipulations on photosynthesis and on the level of carbohydratespresent in the cotyledons was more evident in those seedlingsgrowing under high light intensity (580 µE m^–2 s^–1),than in those exposed to 300 µE m^–2 s^–1 Key words: Sink-source relationship, cotyledons, photosynthesis