A chemosystematic study of some geraniaceae

The flavonoids of five Geranium, fourteen Erodium and four Monsonia species were studied. Quercetin was the most common aglycone with lesse     

Sex allocation of females and hermaphrodites in the gynodioecious Geranium sylvaticum

Seed production and patterns of sex allocation were studied in female and hermaphroditic plants in two gynodioecious populations of Geranium sylvaticum (Geraniaceae). Females produced more flower buds and seeds than hermaphrodites in one of the two study populations. The other female traits measured (pistil biomass, seed number per fruit, individual seed mass) did not differ between the gender morphs. The relative seed fitness of hermaphrodites differed between the study populations, with hermaphrodites gaining less of their fitness through female function in the population with a high frequency of females. However, the amount and size of pollen produced by hermaphrodites did not differ between populations. The number of flower buds was positively correlated with seed production in females, whereas in hermaphrodites a positive correlation between number of buds and seed production was found in only one of the two study populations. These results suggest that fitness gain through female function is labile in hermaphrodites of this species, and is probably affected by environmental factors such as the sex ratio of the population.     

Floral dimorphism, pollination, and self-fertilization in gynodioecious GERANIUM RICHARDSONII (Geraniaceae)

The selective maintenance of gynodioecy depends on the relative fitness of the male-sterile (female) and hermaphroditic morphs. Females may compensate for their loss of male fitness by reallocating resources from male function (pollen production and pollinator attraction) to female function (seeds and fruits), thus increasing seed production. Females may also benefit from their inability to self-fertilize if selfing and inbreeding depression reduce seed quality in hermaphrodites. We investigated how differences in floral resource allocation (flower size) between female and hermaphroditic plants affect two measures of female reproductive success, pollinator visitation and pollen receipt, in gynodioecious populations of Geranium richardsonii in Colorado. Using emasculation treatments in natural populations, we further examined whether selfing by autogamy and geitonogamy comprises a significant proportion of pollen receipt by hermaphrodites. Flowers of female plants are significantly smaller than those of hermaphrodites. The reduction in allocation to pollinator-attracting structures (petals) is correlated with a significant reduction in pollinator visitation to female flowers in artificial arrays. The reduction in attractiveness is further manifested in significantly less pollen being deposited on the stigmas of female flowers in natural populations. Autogamy is rare in these protandrous flowers, and geitonogamy accounts for most of the difference in pollen receipt between hermaphrodites and females. Female success at receiving pollen was negatively frequency dependent on the relative frequency of females in populations. Thus, two of the prerequisites for the maintenance of females in gynodioecious populations, differences in resource allocation between floral morphs and high selfing rates in hermaphrodites, occur in G. richardsonii.     

Identification and characterization of the water gap in physically dormant seeds of Geraniaceae, with special reference to Geranium carolinianum

Background and Aims

Physical dormancy in seeds of species of Geraniaceae is caused by a water-impermeable palisade layer in the outer integument of the seed coat and a closed chalaza. The chalazal cleft has been reported to be the water gap (i.e. location of initial water entry) in innately permeable seeds of Geraniaceae. The primary aim of this study was to re-evaluate the location of the water gap and to characterize its morphology and anatomy in physically dormant seeds of Geraniaceae, with particular reference to G. carolinianum.

Methods

Length, width, mass, anatomy and germination of two seed types (light brown and dark brown) of G. carolinianum were compared. Location, anatomy and morphology of the water gap were characterized using free-hand and microtome tissue sectioning, light microscopy, scanning electron microscopy, dye tracking, blocking and seed-burial experiments.

Key Results

Treatment with dry heat caused a colour change in the palisade cells adjacent to the micropyle. When placed in water, the ‘hinged valve’ (blister) erupted at the site of the colour change, exposing the water gap. The morphology and anatomy in the water-gap region differs from those of the rest of the seed coat. The morphology of the seed coat of the water-gap region is similar in G. carolinianum, G. columbinum, G. molle and G. pusillum and differs from that of the closely related species Erodium cicutarium.

Conclusions

Dislodgment of swollen ‘hinged valve’ palisade cells adjacent to the micropyle caused the water gap to open in physically dormant seeds of G. carolinianum, and it was clear that initial water uptake takes place through this gap and not via the chalazal opening as previously reported. This water gap (‘hinged valve gap’) differs from water gaps previously described for other families in morphology, anatomy and location in the seed coat.     

The autumn effect: timing of physical dormancy break in seeds of two winter annual species of Geraniaceae by a stepwise process

Background and Aims

The involvement of two steps in the physical dormancy (PY)-breaking process previously has been demonstrated in seeds of Fabaceae and Convolvulaceae. Even though there is a claim for a moisture-controlled stepwise PY-breaking in some species of Geraniaceae, no study has evaluated the role of temperature in the PY-breaking process in this family. The aim of this study was to determine whether a temperature-controlled stepwise PY-breaking process occurs in seeds of the winter annuals Geranium carolinianum and G. dissectum.

Methods

Seeds of G. carolinianum and G. dissectum were stored under different temperature regimes to test the effect of storage temperature on PY-break. The role of temperature and moisture regimes in regulating PY-break was investigated by treatments simulating natural conditions. Greenhouse (non-heated) experiments on seed germination and burial experiments (outdoors) were carried out to determine the PY-breaking behaviour in the natural habitat.

Key Results

Irrespective of moisture conditions, sensitivity to the PY-breaking step in seeds of G. carolinianum was induced at temperatures ≥20 °C, and exposure to temperatures ≤20 °C made the sensitive seeds permeable. Sensitivity of seeds increased with time. In G. dissectum, PY-break occurred at temperatures ≥20 °C in a single step under constant wet or dry conditions and in two steps under alternate wet–dry conditions if seeds were initially kept wet.

Conclusions

Timing of seed germination with the onset of autumn can be explained by PY-breaking processes involving (a) two temperature-dependent steps in G. carolinianum and (b) one or two moisture-dependent step(s) along with the inability to germinate under high temperatures in G. dissectum. Geraniaceae is the third of 18 families with PY in which a two-step PY-breaking process has been demonstrated.     

Phylogenetic position of the Hawaiian geraniums based on rbcL Sequences

The seven currently recognized species of Geranium endemic to the Hawaiian Islands are unusual in their shrubby or arborescent habit and unlobed, parallel-veined leaves rather than the palmately cleft or lobed leaves and herbaceous habit typical of the genus. Their placement within the genus and their biogeographic source have been obscured by this morphological distictiveness and the limited resolution of relationships on the basis of morphology in the very speciose subgenus Geranium. Phylogenetic analysis of rbcL gene sequences provides strong support for the monophyly of the Hawaiian group, and indicates that the Hawaiian clade is deeply nested within section Geranium rather than comprising a separate section. The continental relatives studied to date with the greatest similarity in sequence to the Hawaiian group are native to the Americas rather than Asia or the Pacific. The Hawaiian species are extremely similar to one another in rbcL sequence, while the tree topology obtained is consistent with a basal position for Geranium arboreum within the group.     

Volatile constituents of Erodium cicutarium (L.) L’ Hérit. (Geraniaceae)

Essential oils from Erodium cicutarium were obtained by hydrodistillation (samples consisting of entire plants (ec1), leaves and stems (ec2)) and analyzed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC/MS), resulting in a total of 177 components being identified. The essential oils were of a very similar chemical composition and consisted mainly of aliphatic compounds and their derivatives. Fatty acids and fatty acid derived compounds were the most common, 51.3% (ec1) and 60.1% (ec2), followed by carotenoid derived compounds, 12.6% (ec1) and 20.2% (ec2), and then terpenoids, 14.9% (ec1) and 14.2% (ec2). The main constituents in the oils were hexadecanoic acid, 22.8% (ec2) and 35.9% (ec1) and hexahydrofarnesyl acetone, 10.8% (ec2) and 11.6% (ec1). The results obtained differ markedly from those previously reported for the same species.     

The effect of water stress on the life cycles of Erodium crinitum Carolin and Erodium cicutarium (L.) L'Hérit. ex Alton (Geraniaceae)

Abstract Erodium cicutarium (L.) L'Hérit. ex Aiton (Geraniaceae) from temperate Mediterranean Eurasia is naturalized across large areas of arid and semi-arid Australia to which Erodium crinitum Carolin is native. plant size, leaf and bud numbers and fruit/plant biomass ratio were significantly lower under drought, flower and fruit number, fruit size and total mass were unaffected. In contrast, E. crinitum was largely unaffected by the drought conditions, showing only an increase in the fruit/plant biomass ratio.     

Translocation of sitosterol and related compounds in Pelargonium hortorum and helianthus annuus

The translocation of several plant sterols and a triterpene was studied in geranium and sunflower plants. Upward translocation of sitosterol-[¹⁴C] and β-amyrin-[¹⁴C] was shown within 48 hr to the upper parts of a geranium plant sectioned previously above the roots. Downward translocation of sitosterol-[¹⁴C] from the leaf of application was evident in intact plants after 48 hr. In addition to free sitosterol-[¹⁴C] considerable amounts of sitosteryl-[¹⁴C] glycoside and traces of sitosteryl-[^14C] ester were found in most parts examined. Very slow downward translocation of cholesterol-[¹⁴C] but not of desmosterol-[¹⁴C], sitosteryl-[¹⁴C] palmitate or β-amyrin-[¹⁴C] was shown in geranium. In sunflower no downward translocation of cholesterol-[³H], sitosteryl-[³H] acetate or palmitate could be detected. In geranium, sitosteryl-[¹⁴C] glycoside translocated downward from the leaf of application to all other plant parts, except other leaves, and was found in these parts after 10 days as the unchanged glycoside, free sterol and steryl ester. The effect of drying the plant parts on the recovery of radioactive steroidal material is discussed. Traces of a water soluble, dialyzable form of sterol-[¹⁴C] were also detected in dried geranium roots after treatment with strong acid or alkali.