Standard Petal Research Articles

Floral traits and pollinator constancy: Foraging by native bees among three sympatric legumes

Abstract The foraging constancy of the solitary bee, Trichocolletes sp., was documented in a semi‐arid ecosystem where three morphologically similar legumes co‐occur. To quantify the degree of floral similarity among the forage plants, Dillwynia hispida, Dillwynia uncinata and Pultenaea densifolia, discriminant function analysis of petal dimensions and a spectral analysis of corolla colour was undertaken. Petal size varied moderately among species resulting in 2–14% of specimens being misclassified, usually as D. uncinata. Subtle variation in corolla colour in the ultraviolet wavelengths contributed to the distinctiveness of each species. All three species exhibit an UV‐absorbing region at the base of the standard petal which contrasts sharply with the rest of the UV‐rerlecting petal. Between 450 nm and 470 nm, per cent reflectance drops for D. hispida and P. densifolia, but remains steady for D. uncinata. Above 480 nm, parts of the standard petal in all species reflect similar amounts of light with little variation exhibited among species. Nectar was only offered by D. hispida and D. uncinata, whereas P. densifolia produced an excess of pollen which may serve as a reward. Despite the subtle differences in floral morphology and rewards among these sympatric legumes, Trichocolletes bees only remained faithful to a given species in 43% of 183 interplant flights. Inconstant foraging by Trichocolletes sp. increases the pool of resources because rewards in all three legume species can be obtained in exactly the same manner.

Control of Plum Curculio, 1991

Abstract Test 1 was set up to compare effectiveness of different schedules of Asana, Guthion, and Lorsban. Treatments were arranged in a randomized block design and replicated three times on single tree plots of'McIntosh' apples. These trees were 25 years old, 4.6 m high, and planted on seedling rootstocks 5.8 × 12.5 m apart. Plots were separated by one or more unsprayed buffer trees. Sprays were applied dilute to runoff with a hand sprayer (32 kg/cm2) at pink (1 May), petal fall (14 May), first cover (24 May), and second cover (5 Jun). Fruit damage was evaluated on 14 Aug by examining 50 dropped and 100 picked apples from each tree for both feeding damage and oviposition scars. Test 2 was set up to compare effectiveness of post petal fall border row treatments versus complete sprays of Guthion in controlling plum curculio. The following treatments were compared: (1) Standard Plot—All trees in each plot were sprayed with Guthion 35 W (11.6 oz form/100 gal) at petal fall (14 May), first cover (24 May) and second cover (5 Jun); (2) Standard Petal Fall—All trees were sprayed with Guthion 35 W (11.6 oz form/100 gal) at petal fall (14 May); (3) Border Row Plot—All trees were sprayed at petal fall (14 May) with Guthion and trees along the perimeter of plots were sprayed at first cover (24 May) and second cover (5 Jun). These border sprays were applied to single trees around the perimeter of plots in Orchard 12 and to the two outer rows of trees around the perimeter of plots in Orchard 12B. Each treatment was replicated four times. Two replications were set up in rectangular 9-tree plots of 'McIntosh' apples in Orchard 12. Trees in these plots were 25 years old, 4.6 m high, and planted on seedling rootstocks 5.8 × 12.5 m apart. Another two replications were set up in rectangular 24-tree plots in Orchard 12B. Trees in this orchard were 12 years old, 3.2 m high, and planted on M111/M9 interstem rootstocks 8.5 × 4.6 m apart. Trees in Orchard 12B were planted in three 8-tree rows consisting of two adjacent 'McIntosh', 'Cortland', 'Golden Delicious', and 'Delicious' trees. Fruit damage was evaluated on 14-15 Aug by examining 50 dropped and 100 picked apples from the center 'McIntosh' tree in each plot in Orchard 12 and 50 picked apples from each of two trees (one 'Golden Delicious' and one 'Cortland') in the center of each plot in Orchard 12B.

Physical and biochemical characteristics ofParkinsonia aculeataL. andPongamia pinnataVent. flowers

SUMMARYParkinsonia aculeata and Pongamia pinnata are important summer food plants for a variety of wild solitary and social bees (Apoidea) in northern India. Studies were thus carried out on these two species in Hisar, India, in order to assess the relative importance of various physical and biochemical characteristics of the flowers in regulating nectar foraging by bees. The nectar of P. pinnata is accessible directly through the corolla tube either at a place between the keel and the standard petal or at the sides of the standard petal. P. aculeata has a conspicuous flag petal marked with red spots which guide foraging insects to the nectary. Colorimetrie analysis showed that P. aculeata flowers contained higher quantities of UV-reflective carotenoids than those of P. pinnata. P. pinnata flowers secreted 1.05 ± 0.06 μl nectar containing 34.8% sugars, with almost equal amounts of sucrose and glucose, within 2–3 h of anthesis. In the same period, P. aculeata flowers secreted 0.24 ± 0.08 μl nectar containi...

Structure, distribution and taxonomic significance of trichomes in someIndigofera L. (Fabaceae)

Structure and distribution patterns of the trichomes occurring on the standard petals in 8 species ofIndigofera L. have been investigated. In all, 4 trichome types exhibiting 7 distribution patterns have been recognised. Their taxonomic significance has been shown by providing a key for the identification of the species studied.

INHERITANCE OF CRESENT COLOUR ON STANDARD PETAL IN GROUNDNUT (Arachis hypogaea L./

The study of F2 plants of intraspecific hybrid between the varieties having purple veins in the standard petal and varieties lacking the purple colour showed a segregation in the ratio of 3:1 for purple colour and for its absence. Hence it is evident that the character is governed by single dominant gene. Since the ratio is identical in both direct and reciprocal crosses, the influence of cytoplasm is tuled out.

Stigma Development and the Stigmatic Cuticle of Alfalfa, Medicago sativa L.

In Medicago sativa L., the stigma of young flowers is oval in face view and develops a fringe of nonsecreting hairs. A bilayered cuticle 120 nm thick covers the stigmatic tissue, which is composed of cylindrical cells heavily loaded with lipid droplets. During secretion of stigmatic exudate, lipid is lost from the cytoplasm, where it appears to be broken down through association with vacuoles. Vertical files of secreting cells become separated along lateral cell walls and form a copious stigmatic exudate composed chiefly of dense globules, apparently lipid. The cuticle remains attached to the outer, tangential wall of each cell file but stretches across spaces between files to confine exudate and act as a barrier between self-pollen and stigmatic fluid. In untripped flowers, the stigmatic cuticle is apparently not an absolute barrier to self-pollination and resultant autogamy. With artificial tripping, the stigma is mashed against the standard petal. The stigma face becomes concave, with self-pollen embed...

The taxonomic value of floral characters in tribe Trigonelleae (Leguminosae), with special reference to Medicago

The legume tribe Trigonelleae comprises Medicago (with M. arborea sometimes segregated as the monotypic genus Rhodusia), Melilotus, Trigonella, and the monotypic Factorovskya. The wisdom of segregating the two monotypic genera may be questioned, and many species have been claimed to represent intergrading variation between Medicago and either Melilotus or Trigonella, or between the latter pair. Previous morphological studies have not provided a satisfactory means of resolving generic delimitation in the Trigonelleae. In the present investigation numerical taxonomic analysis (agglomerative clustering and ordination) of floral characters indicated that Medicago, Melilotus, and Trigonella could be distinguished on the basis of combinations of floral attributes, although no single characteristic was capable of separating them completely. Trigonella section Bucerates proved to be quite distinctive from the remaining species of Trigonella examined. Limited evidence was found for segregating Medicago arborea as a monotypic genus. Factorovskya aschersoniana proved distinctive, but its relationships remain enigmatic. Discriminant analysis was employed to test the affinities of "problematical" species allegedly intermediate between Medicago, Trigonella, and Melilotus. Most of the putatively intermediate species proved to be much closer to one of the genera than to the others. A syndrome of morphological features was discovered to separate the Trigonelleae into two classes of plants, the one group including Medicago, Factorovskya, and Trigonella section Bucerates, and the other comprising Melilotus and the remaining examined species of Trigonella. The former group contrasts with the latter by possessing interlocking wing and keel petals, relatively less apical fusion of the keel petals, and relatively well-developed wing petal horns; and by having a greater frequency of species with dilated filaments, with staminal tubes which are conical at the apex rather than blunt, and with standard petals having more than three clusters of veins. The latter three differences, however, are less frequent between the two groups than the first three. The floral syndrome could reflect adaptation of the former group of plants to outcrossing (perhaps relictual adaptation in the inbreeding species) by means of the "tripping" mechanism which is well-known in Medicago. If so, the taxonomic significance of the syndrome is difficult to ascertain, as it may have developed independently in the different genera in which it occurs.

Some Aspects of the Developmental Anatomy of Arachis hypogaea L.

Studies of the different stages of the embryo of Arachis hypogaea L. revealed that the root apex and cotyledons are initiated in the globular embryo. The root cap is formed in the heart-shaped embryo but it does not persist in the mature one, its place being occupied by cortical files. There is a common initiating region for the columella and provascular strands at the radicular apex. The cortical files “open out”, exhibit knee joints, and contribute secondary columella files. The radicular apex becomes distinct before the plumular apex. The protoderm of the “embryonic shoot apex” is not stable in the heart-shaped embryo but becomes stabilised in the later stages. The mature shoot apex exhibits four cytohistological zones. The floral anatomy shows some peculiar features like one staminal trace fusing with the trace of the standard petal, and the tendency for reduction in the androecium. The node is trilacunar. The nuclear endosperm is meagerly developed and has cytoplasmic nodules. A hypostase is also developed.

Nature of the Variation in Flower Colour in Vicia

FROM earlier work it was concluded that the principal factor concerned in promoting blueness in anthocyanin-pigmented flowers of Lathyrus species was the presence of flavonol co-pigments1,2. It was of interest to extend the observations into the related genus Vicia to determine whether a similar conclusion might be reached. In the latter genus the range of flower colour is similar to that found in Lathyrus. Species were selected for investigation which gave some representation of the colour range. Hydrolysed extracts of standard and wing petals were prepared and then examined by filter paper chromatography as described earlier1.

Colour Change in Flowers of Lathyrus hirsutus during Senescence

ALTHOUGH there has been some work on the nature of changes in flower colour during development1–3, little is known about changes during senescence. The anthocyanin-pigmented flowers of Lathyrus hirsutus L. exhibit as they age a well marked colour change immediately before the petals show obvious loss of turgor. The mature standard petal is bluish red and it fades through blue to greenish blue; the wing petals are pale blue and fade to greenish blue. It was suggested in earlier work that blueness in mature flowers of Lathyrus species is promoted by flavonol glycoside co-pigments3–5. Thus it was found that the blue wing petals of L. hirsutus contain greater quantities of co-pigment relative to anthocyanin than the standard petals4. In this species the pH of the expressed sap of the wings was found to be rather higher than that of the standard petal, and it was suggested that this pH difference might contribute to the bluer appearance of the wing petal.

Development of Anthocyanin Pigmentation in Flowers ofLathyrus odoratus

A quantitative study has been made of developmental changes in the antho cyanins and a flavonol glycoside in the red/blue bicoloured flowers of Lathyrus odoratus L. Anthocyanin formation occurs during the period of most rapid growth of the petals. At maturity about four times as much anthocyanin is present in the standard petal as in the pair of wing petals, which are together comparable in fresh weight to the standard. The pattern of development of flavonol glycoside is quite different; some are formed well before anthocyanin formation occurs and at maturity about six times as much flavonol glycoside is present in the wings as in the standard per unit amount of anthocyanin. Some further evidence is thus provided that the flavonol glycoside may be acting as a co-pigment which modifies the wing petal colour to blue.

CHARACTERISTICS OF ALFALFA FLOWERS AND THEIR EFFECTS ON SEED PRODUCTION

Several characteristics and properties of the alfalfa flower were studied to determine their role in seed setting and to provide a basis for the evaluation of mutant flowers for pollination by honeybees. Ease of tripping varied with plant and with age of floret. Nectar was secreted at a uniform daily rate for 4–5 days after the flowers opened. Nectar absorption was similar to secretion for 2 days but then accelerated. Removal of nectar had no effect on seed setting. Ovules were viable from opening to wilting of the flowers. Age of floret did not affect seed production after self-fertilization but, after cross-fertilization there was a gradual decline after 3 days. Pollen from untripped florets decreased slightly in germination with age, but remained viable after 10 days’ storage in a honeybee colony. Pollen-collecting honeybees effectively cleaned themselves of pollen in 2 days. Seed production was not increased by repeated visits of honeybees to tripped flowers, and cross-fertilization was not increased by dusting pollen on plants before tripping. Ovules of florets with exposed stigmas remained fully functional for up to 6 hours but then declined rapidly to llmost 0 at 48 hours. Foreign pollen was still 50% effective when applied 24 hours after self-pollination. Self- and cross-fertilized seeds were intermingled in the pods but self-fertilized seeds did not occur beyond the fourth position from the proximal end. It is suggested that extent of honeybee pollination may be improved by providing an alfalfa flower either with an exposed stigma or with a vestigial standard petal combined with delayed sell-tripping.

Some observations on the tripping of alfalfa (Preliminary report)

This paper is a preliminary report of tripping experiments ot alfalfa (Medicago sativa) flowers. The staminal column and stigma of this flower were anatomically studied and the results obtained are as follows: In the transverse section of the staminal tube, the lower part of this organ is thicker than the upper part in width and the cell size of the former is larger than that of the latter. In the longitudinal section, the external cells of the staminal column are thicker in width and longer in length than those of the inner cells. Cuticule-like membranes were found on the stigmatic surface and granular fatty substances were secreted in the space between the stigma projection and the stigmatic membrane. However the structure of the stigma remarkably differs from what JOST has found on the stigma of Cytisus and Lupinus. The turgor pressure at the outer tissue of the staminal tube was higher 1.1 atmospheric pressure than that of the inner tissue. The motive power of tripping exists in the staminal column but not in the pistil. The pod setting of alfalfa was increased remarkably by artificial tripping compared with that of non-treatment, but when the standard petal was removed and tripped artificialy the fertilization of this plant was almost same to the case of non-treatment. The authors consider that the scope of tripping on the increased seed setting is in the confliction of stigma and standard petal. It is a problem to investigate minutely in future that the confiction of those organs produce results to either the scattering of pollen, the destruction of the stigmatic membrane or the both.