Determination Of Pollination Syndromes And Breeding Systems Of Selected Flowers

Determination of pollination synDromes anD breeDing systems of selecteD flowers Sachith S. Fernando, Department of Botany, University of Kelaniya, Sri Lanka.

1

Objectives o To determine the pollination syndromes of selected 10 flowers by looking at their floral morphology

o To determine the breeding systems of selected 10 flowers by using out crossing index (Cruden, 1977)

o To infer the breeding systems of selected 10 flowers by using pollen: ovule ratio

o To determine the pollination syndromes of selected 10 flowers by using “Harmonic” relations between pollinators and perianth shape & color

2

Introduction Plant breeding systems have been viewed as mechanisms to promote outcrossing (or as mechanisms to prevent inbreeding). As mentioned above, hermaphrodites are common in plants, while much fewer species are dioecious. Dioecy is easily seen as a mechanism to prevent inbreeding, since male and female flowers exist on separate plants. Hermaphrodites, on the other hand, must evolve other mechanisms to prevent selfing, or at least, to reduce inbreeding depression (i.e. the accumulation of deleterious, recessive alleles). Below is a list of some types of breeding systems: 1. Spatial and Temporal o

dichogamy (protandry and protogyny)

o

herkogamy

o

sex switching

2. Self-Incompatibility (SI) o

homomorphic SI (gametophytic and sporophytic)

o

heteromorphic SI (distyly and tristyly)

3. Sex Expression o

monoecy, dioecy, gynodioecy, etc.

Dichogamy refers to temporal separation in male and female functions of bisexual (or perfect flowers). Protandry occurs when pollen sheds first, before the stigmas become receptive. Protogyny, on the other hand, occurs when the stigmas become receptive first, before pollen is released. Protandry is more common than protogyny. In order for dichogamy to be an effective outcrossing mechanism, all flowers on the plant must be synchronous (i.e. if protandry occurs, all flowers must release their pollen before the stigmas become receptive). Otherwise, pollen can be transfered from one flower to another on the same plant (this is referred to as “geitonogamy”). 3

Dichogamy can also work if there is a sequential developmental pattern of male and female flowers (i.e. certain pollinators tend to move ‘up’ a plant - if flowers are male first, and develop into female flowers starting from the bottom of the plant, then the chances of geitonogamy can be reduced). Herkogamy is the spatial separation of styles and anthers in a perfect flower. This system is apparently widespread; however, geitonogamous pollen transfer is possible. In flowers that do not have spatial separation of styles and anthers, self pollination can occur. Sex-switching simply refers to a plant that is either male or female at one time, and then later (perhaps later in the growing season), the plant switches to the opposite sex. Self-incompatibility is the inability of a hermaphroditic plant (that is capable of producing functional gametes) to set seeds when it is self-fertilized or fertilized by ‘like’individuals. Self-compatibility, on the other hand, refers to a plant’s capability of setting seeds when self-fertilized. There are two types of self-incompatibilty: homomorphic selfincompatibility and heteromorphic self-incompatibility. Homomorphic self-incompatibility occurs when there is a self-incompatible system in a species where all individuals in a population look identical (that is, all flowers are morphologically similar). Heteromorphic selfincompatibility (or heterostylous self-incompatibility) occurs when there are two or more different morphs in the population (i.e. in perfect flowers, the styles and stamens are of different lengths). Homomorphic self-incompatibility can be recognized as two types; gametophytic, or sporophytic. In the gametophytic type, there is a single locus (the ‘S’-locus) which has many different alleles (e.g. S1, S2, S3, S4, etc). If a pollen grain has an allele that is also possessed by the recipient, the pollen is rejected (i.e. fertilization does not occur). Similarly, pollen is rejected in sporophytic self-incompatibility if the recipient has either of the alleles present in the pollen donor. It is called ‘gametophytic’ self-incompatibility, because only one parental allele is expressed in the pollen. Conversely, both parental alleles are expressed in the pollen grain in sporophytic Self-incompatibility (even though the pollen may only contain one allele -- thus, 4

there is a parental effect with the sporophytic system). Gametophytic SI is found in Oenothera sp., as well as in the Solanaceae (potato family), Papaveraceae (poppy family), Poaceae (grass family), Ranunculaceae (buttercup family), and the Rosaceae (rose family, e.g. apples). Sporophytic self-incompatibility is found in the Brassicaceae (mustard family), Asteraceae (aster family), and the Convolvulaceae. It had been oringially thought that self-incompatibility systems were responsible for the success of the angiosperms (i.e. self-incompatibility was considered to be an ancestral trait in the angiosperms). By comparing these different systems, it is now known that self-incompatibility arose independently on numerous occassions (e.g. some genes involved in these systems have been sequenced and compared -- these genes encode very different products in different species). Heteromorphic (or heterostylous) self-incompatibility is the occurrence of different reproductive morphs in a population. Distyly is fairly common (i.e. it has been found in 25 different families, such as the Primulaceae, Polygonaceae, Menyanthaceae, and Turneraceae), whereas tristyly is very rare (i.e. it has been demonstrated in only three families: the Oxalidaceae, Lythraceae, and Pontederiaceae, and possibly in the Amaryllidaceae). There are a number of differences in the different pollen and style types. In Distyly, there are only two morphs (longs and shorts). Tristyly, on the other hand, has three morphs (longs, mids, and shorts). Flower is the sexual reproductive structure of the Angiosperms, adapted for pollination. The flower consists of a determinate, modified shoot (the floral axis or receptacle) bearing modified leaves (the perianth parts, stamens and/or carpels). There are two types of flowers; an ‘imperfect’ flower has either male or female components, but not both. A ‘perfect’ flower has both male and female components. A perfect flower is also known as a hermaphrodite or as a ‘bisexual’ flower. Pollination is the deposition of mature pollen/s on receptive stigma of the same flower or some other flower of the same species. In pollination the male and female gametes are mixed to produce the offspring. According to pollination type the angiosperms are of two categories; Allogamous plants and Autogamous plants. Allogamous plants highly rely on out breeding

5

(cross pollination) with other individuals of the species, whereas Autogamous plants rely on selfing (self pollination). The allogamous plants have to transfer the pollens from one plant to another. Therefore they should employ many pollen transfer systems. These pollen transfer systems can be commonly referred to as pollination syndromes. Pollination syndromes Abiotic pollination syndromes

Biotic pollination syndromes

Abiotic pollination syndromes Wind pollination (anemophily) Flowers may be small and inconspicuous, green and not showy. They produce enormous numbers of tiny pollen grains (hence wind-pollinated plants may be allergens, but seldom are animal-pollinated plants allergenic). They have large feathery stigmas to catch the pollen grains. They grow in low-diversity stands and are among the taller species in their communities. Insects may visit them to collect pollen, but they are not the most effective pollinators and exert little selection pressure on them.

Water pollination (hydrophily) Water-pollinated plants are aquatic. Their flowers tend to be small and inconspicuous with lots of pollen grains and large, feathery stigmas to catch the pollen. Many aquatic plants are insectpollinated, with flowers that emerge into the air.

Biotic pollination syndromes Beetle pollination (cantharophily) Beetle-pollinated flowers are usually large, greenish or off-white in color and heavily scented. Scents may be spicy, fruity, or similar to decaying organic material. Most beetlepollinated flowers are flattened or dish shaped, with pollen easily accessible, although they may 6

include traps to keep the beetle longer. The plant's ovaries are usually well protected from the biting mouthparts of their pollinators. Beetles may be particularly important in semi-desert areas, like South Africa and southern California.

Fly pollination (myophily and sapromyophily) There are two types of fly pollination: myophily and sapromyophily. A diversity of flies (particularly bee flies (Bombyliidae), hoverflies (Syrphidae), etc.) feed on nectar and pollen as adults, and regularly visit flowers, while male fruit flies (Tephritidae) are attracted to and feed on specific floral attractant, which acts as fly's sex pheromone precursor or booster, of some wild orchids (Bulbophyllum species - with highly moveable lip) that do not produce nectar. These are the myophiles. Sapromyophiles, on the other hand, normally visit dead animals or dung. They are attracted to flowers that mimic these odoriferous items. They obtain no reward and would quickly leave, but the plant may have traps to slow them down. These plants have a strong, unpleasant odor, and are brown or orange in color. They are not as common as myophilous plants. Myophilous plants do not tend to have a strong scent, and tend to be purple, violet, blue, and white, open dishes, or tubes. Flies generally utilize many different sources of food making their pollinating activity infrequent and unreliable. However, their sheer numbers and the presence of some flies throughout the year make them important pollinators for many plants. Flies tend to be important pollinators in high-altitude and high-latitude systems, where they are numerous and other insect groups may be lacking.

Bee pollination (melittophily) Bee-pollinated flowers tend to fall into two classes: 1. Showy, open, bowl-shaped flowers that are relatively unspecialized (e.g. wild roses, sunflowers) 2. Showy, complicated, non-radially symmetric flowers that are more specialized (e.g. peas, foxgloves)

7

Some bee flowers tend to be yellow or blue, often with ultraviolet nectar guides and scent. Nectar, pollen, or both are offered as rewards in varying amounts. The sugar in the nectar tends to be sucrose-dominated. There are diverse types of bees, however. Honeybees, bumblebees, orchid bees, etc are large groups that are quite distinctive in size, tongue length and behavior (some solitary, some colonial). Thus generalization about bees is difficult. Some plants can only be pollinated by bees because their anthers release pollen internally, and it must be shaken out by buzz pollination. Bees are the only animals that perform this behavior. Bee pollination from mobile beehives is of great economic value for orchards such as apple or almond.

Butterfly pollination (psychophily) Butterfly-pollinated flowers tend to be large and showy, pink or lavender in color, frequently have a landing area, and are usually scented. Since butterflies do not digest pollen (with one exception), more nectar is offered than pollen. The flowers have simple nectar guides with the nectaries usually hidden in narrow tubes or spurs, reached by the long tongue of the butterflies.

Moth pollination (Phalaenophily and Sphingophily) The plants that are pollinated by moth (nocturnal butterflies) are called sphingophilous or phalaenophylous plants. These plants have large nocturnal white flowers whit a strong sweet scent. These features allow moths that are active at night to find the flowers from afar. The moth stay on the wing while inserting their long tongue into the deep nectar container, These plant comprise the longest nectar bearing flowering tubes known in the plant kingdom.

Bird pollination (ornithophily) Although hummingbirds are the most familiar nectar-feeding birds for North Americans, there are analogous species in other parts of the world: sunbirds, honeyeaters, flowerpeckers, 8

honeycreepers, bananaquits, flowerpiercers, lories and lorikeets. Hummingbirds are the oldest group, with the greatest degree of specialization on nectar. Flowers attractive to hummingbirds that can hover in front of the flower tend to be large red or orange tubes with a lot of dilute nectar, secreted during the day. Since birds do not have a strong response to scent, they tend to be odorless. Perching birds need a substantial landing platform, so sunbirds, honeyeaters, and the like are less associated with tubular flowers.

Bat pollination (chiropterophily) Bat-pollinated flowers tend to be large and showy, white or light coloured, open at night and have strong odours. They are often large and bell-shaped. Bats drink the nectar, and these plants typically offer nectar for extended periods of time. Sight, smell, and echo-location are used to initially find the flowers, and excellent spatial memory is used to visit them repeatedly. In fact bats can identify nectar-producing flowers using echolocation, a talent that was only recently discovered. In the New World, bat pollinated flowers often have sulfur-scented compounds, but this does not carry to other parts of the world. Bat-pollinated plants have bigger pollen than their relatives.

9

Determination of pollination syndromes using floral characters

10

Mode of Pollination

Visitation & Anthesis

Beetles (cantharophily)

Day & Night

Actinomorphic, numerous floral parts; large bowl shaped, ovules protected

Dull, white, few visual attractions, no nectar guides

Strong, fruity or aminoid; no nectar, food primarily pollen or food bodies

Carrion & Dung Beetles & Flies

Day & Night

Actinomorphic, deep corolla tube with appendages forming traps

Purple, brown (like meat), no nectar guides or nectar

Strong, like rotting meat, really awful

Flies (myophily and sapromyophily)

Mostly day

Actinomorphic, little depth

Variable, but often dull or light, nectar guides present

Little to (too) much odor, nectar present or absent, accessible, food often pollen

Bees (melittophily)

Day

Often zygomorphic, shape variable, little depth to tubular

Yellow, blue, or white, usually not red, often with nectar guides

Sweet odor, nectar usually present, often hidden

Butterflies (psychophily)

Day

Actinomorphic, erect anthers on narrow tubular corolla, have landing flatforms

Yellow , blue , pink and red , often with nectar guides

Strong or weak, A lot of nectar present in corolla tubes or spurs

Mode of Pollination Moths (phalaenophily and Sphingophily)

Visitation & Anthesis Night or evening

Flower Morphology

Flower Morphology

Actinomorphic, narrow tubular corolla, anthers often, versatile, flowers horizontal or hanging down

Color

Color

White or sometimes pale green to yellow, no nectar guides

Odor

Odor

Heavy, sweet odor at night, abundant nectar 11

Determination of breeding systems using out crossing index (Cruden, 1977) This is a method to tentative determination of breeding system by looking at the floral morphology. Floral character

Ranking

•

Diameter of the flower/ inflorescence Up to 1 mm 1-2 mm 2-6 mm More than 6 mm

•

Temporal separation of the anther dehiscence and stigma receptivity Homogamy, protogyny 0 Protandry 1

•

Spatial positioning of the stigma and anthers Same level Spatially separated

0 1 2 3

0 1

Sum of out crossing values will be provided the following predictions. OCI values; 0 = Cleistogamy 1 = Obligate autogamy 2 = Facultative autogamy 3 = Self compatible, some demand for pollinators 4 = partially self compatible, out crossing, demand for pollinators

12

Pollen: Ovule ratio, as a method of estimating the breeding systems Use of pollen ovule ratio as a method of estimating the breeding system was developed by Cruden R.W. (1977) Pollen: Ovule ratio (P:O) =

Average number of pollen grains per flower Average number of ovules per flower

According to Cruden, pollen:ovule ratio can be classified into 5 major categories. Pollen: Ovule ratio range

Breeding system

2.4-5.4

Cleistogamy

18.1-39

Obligate autogamy

31.9-396.0

Facultative autogamy

244.7-2588

Facultative xenogamy

2108-195525.0

Obligate xenogamy

13

Determination of pollination syndromes using floral characters “Harmonic” relations between pollinator and perianth shape and color (greatly simplified, adapted from faegri and van der Pijl,1979). Structural blossom class a Dish or bowl Bell

Pollinator class

(unf,a)

beetles

(unf or f,a)

Color preference (Human visual Spectrum) brownish or dull

flies white or cream syrphids

Gullet

(f,z)

bees

Flag

(unf or f,z)

yellow

bats

Trumpet

(f,a or z)

moths blue or purple

Brush

(o,a or z)

butterflies

orange and red

birds Tube

(f, a or z)

unf - corolla unfused a – corolla actinomorphic

green f – corolla fused z – corolla zygomorphic 14

Materials and method Determination of pollination syndrome using floral morphological characters Flower shape, corolla type, petal color, flower/inflorescence size, reward type and amount, timing of the ten flowers were determined. Pollination syndromes were determined regarding to the above floral characteristics

Estimation of breeding system by using pollen ovule ratio (P:O ratio) o Pollen counting Ripe anther was selected from each of the flowers of the each species and was dissolved in distilled water (0.5 mL). One drop (0.05 mL) from the above prepared suspension was placed on a microscopic slide and the number of pollens was counted under light microscope. Two replicates were done for each flower. o Ovule counting Number of ovules in each flower was counted by observing cross sections of ovaries under dissecting microscope. Two replicates were done for each flower. Then the pollen ovule ratio of each flower was determined.

Determination of breeding system by using outcrossing index Diameter (of the flower or inflorescence), spatial and temporal separation of the selected 10 flowers were determined. Two replicates were done for each flower. Outcrossing index for each of the flowers was determined. Here stigmatic receptivity was observed by immersing the stigma in Hydrogen peroxide (H2O2).

15

Results and Calculations Determination of pollination syndrome by using floral morphological characters

16

Traits of flower Name of the flower

Timing

Pollination syndrome

Day

Ants

Pollens, Floral tissues

Day

Butterflies

Pink

Watery nectar, Floral tissues

Day

Butterflies, birds

Shape

Size

Colour

Clitoria ternatea (Katarolu)

Papilionate Zygomorphic

Small

Blue

Cassia fistula (Ehela)

Zygomorphic

Medium

Yellow

Reward type & amount Floral tissues, No scent and nectar

Nerium oleander (Kaneru)

Bell shape Medium Actinomorphic

Mirabilis jalapa (Hendirikka)

Tubular Actinomorphic

Small

Bright purple

Strong pleasant odor, watery nectar

Dawn

Moths, butterflies

Sesbania grandiflora (Katurumurunga)

Papilionate Zygomorphic

Medium

white

No scent

Day

Bees, ants

Bell shape medium Actinomorphic

Yellow

Day

Birds, ants

Actinomorphic

White colour

Strong plescent odor, Some amount of watery nectar Strong pleasant Odor, Nectar present

Day

Ants, beetles, flies, bees

Tecoma stans (Kelanitissa)

Gardenia grandiflora (Gardenia)

Large

17

Determination of breeding systems using out crossing index (Cruden, 1977) Name of the flower

Floral character a) 24 mm b) Protogyny c) Spatially separeted

Rank

Cassia fistula (Ehela)

a) 140 mm b) Protogyny c) Spatially separated

3 0 1

4

Nerium oleander (Kaneru)

a) 126 mm b) Homogamy c) Same level

3 0 0

3

Self compatible, some demand for pollinators

Mirabilis jalapa (Hendirikka)

a) 23 mm b) Homogamy c) Same level

3 0 0

3

Self compatible, some demand for pollinators

Sesbania grandiflora (Katurumurunga)

1) 102 mm 2) homogyny 3) same level

3 0 0

3

Self compatible, some demand for pollinators

Tecoma stans (Kelanithissa)

a) 38mm b) Protogyny c) Spatially separaed

3 0 1

4

Gardenia grandiflora (Gardenia)

a) 62 mm b) Homogamy c) Same level

3 0 0

3

Clitoria ternatea (Katarolu)

3 0 1

OCI value 4

Breeding system Partially self compatible, out crossing, demand for the pollinators Partially selfcompatible, out crossing demand for pollinators

Partially self compatible, out crossing, demand for the pollinators Self compatible, some demand for pollinators

18

Cerbera manghas (Kaduru)

a) 52 mm b) homogyny c) same level

3 0 0

Self compatible, some demand for pollinators

Cesalpina pulcherrima (Monara mal)

a) 33 mm b) Protogyny c) Spatially separated

3 0 1

4

Partially self compatible, out crossing, demand for the pollinators

Camellia sinensis (Tea)

a) 43mm b) Homogyny c) Spatially separated

3 0 1

4

Partially self compatible, out crossing, demand for the pollinators

3

a - Diameter of the flower/inflorescence b - Temporal separation of the anther dehiscence and stigma receptivity c - Spatial positioning of the stigma and anthers

Pollen: Ovule ratio, as a method of estimating the breeding systems Clitoria ternatea No. of anthers per flower No. of pollens per drop (0.05 ml) of suspension No. of pollens per 0.5 ml of suspension (No. of pollens per anther) No. of pollens per flower No. of ovules per flower

= (9+9)/2 =9 = (164 +146)/2 = 155 = 155/0.05*0.5 = 1550 = 1550*9 = 13950 = (5+5)/2 =5

Name of the flower

No. of anthers per flower

No. of pollens per anther

No. of pollens per flower

Clitoria ternatea (Katarolu)

9

1550

13950

No. of ovules per flower 5

Pollen: Ovule ratio

Breeding system

2790

Obligate xenogamy

19

Cassia fistula (Ehela)

7

42400

296800

60

4946.67

Nerium oleander (Kaneru) 30

Mirabilis jalapa (Hendirikka)

13

390

1

390

Obligate xenogamy

Facultative autogamy or facultative xenogamy Facultative xenogamy

5

48

240

1

240

Sesbania grandiflora (Katurumurunga)

9

7560

68040

25

2721.6

Obligate xenogamy

Tecoma stans (Kelanithissa)

4

660

2640

4

660

Facultative xenOgamy

7

2120

14840

1

14840

Cerbera manghas (Kaduru)

5

12

60

2

30

Obligate autogamy

Cesalpina pulcherrima (Monara mal)

10

114

1140

9

126.67

Facultative autogamy

Camellia sinensis (Tea)

180

240

43200

10

4320

Obligate xenogamy

Gardenia grandiflora (Gardenia)

Obligate xenogamy

20

“Harmonic” relation between pollinators and perianth shape and colour Name of the flower

Structural blossom class

Clitoria ternatea (Katarolu) Cassia fistula (Ehela)

Papilionate (unf, z)

Colour preference (human visual spectrum, HVS) Blue

Pollinator class

Dish shape (Unf, z)

Yellow

Syrphids, bees, butterflies Bees

Nerium oleander (Kaneru)

Trumpet shaped (f, a)

Pink, white, purple

Moths, butterflies

Mirabilis jalapa (Hendirikka)

Trumpet shaped (f, a)

Bright purple, pink, yellow, white

Butterflies, moths

Sesbania grandiflora (Katurumurunga) Tecoma stans (Kelanithissa)

papilionate (gullet) (unf, z)

White or cream

Syrphids, bees, bats

Bell (f, a)

Yellow

Flies, syrphids, bees moths, butterflies

Gardenia grandiflora (Gardenia)

Dish shape (Unf, a)

White

Beetles, flies, bees

Cerbera manghas (Kaduru)

Trumpet (f, a)

White

Moths

Cesalpina pulcherrima (Monara mal)

Bowl shape (Unf, z)

Orange, red

Butterflies

Camellia sinensis (Tea)

Dish shape (Unf, a)

White, yellow

Beetles, flies, bees

21

(Unf, corolla unfused; f, corolla fused; a, corolla actinomorphic; z, corollo zygomorphic)

Discussion Floral morphological characters play an important role in the determination of pollination syndrome of a particular flower, because flower shape, color, type of reward, amount of reward and timing are the deciding factors of the pollination syndrome which is employed by a particular flower. The magnolia family (Magnoliaceae) is considered by taxonomists to be one of the least derived angiosperm families. The flowers are relatively simple with parts arranged in whorls and having a somewhat leaf-like appearance. There are no specialized morphological adaptations to exploit pollinators. Insects simply crawl around on the flowers looking for the nectar reward and become dusted by pollen if they crawl over the strap-like anthers. Relatively unintelligent insects like beetles can potentially act as pollinators of this group. Wind-pollinated flowers In general are green, small, and often lack petals. The anthers and stigmas generally hang outside the flowers to allow the wind to carry the pollen. As insects, bees are relatively intelligent and are able to learn how to locate and operate particular species of flowers that are in bloom at a particular time. They are also relatively strong and are able to push their way into complicated flowers that are not accessible to other insects. Bee vision is most sensitive toward the violet end of the spectrum. Therefore, beepollinated flowers tend to have blue or violet markings. Some may even have markings that are only apparent in the UV range. Bee-pollinated flowers often have a lobe that serves as a landing pad. Anthers often are located at the top of tubular petals, dusting the back of the bee as it enters.

22

Plants employ a number of methods to make their flowers more noticeable to pollinators. All members of the large and successful Asteraceae (sunflower) family have composite inflorescences containing many flowers arranged to draw attention to the display. Some flowers produce a bad smell and have a purplish color to simulate the rotting flesh of dead animals. These flowers attract beetles and carrion flies that pollinate the plant as they are fooled into trying to lay eggs on the flower. This group includes the Araceae family, which produces highly modified flowers. Many hummingbird pollinated flowers are red, a color to which bird eyes are sensitive, but which is not as apparent to insects. The hummingbird must hover and reach deep inside the flower to reach the reward. Different species of flower may dust the bird at different locations on its body so that its pollen will be more likely to end up on another species of the same kind. These flowers usually do not have a strong odor because the hummingbirds do not have a particularly well-developed sense of smell. Moth-pollinated flowers are usually white and have a strong scent. These features allow moths that are active at night to find the flowers. The experiment was done to determine the pollination syndrome and breeding system of ten selected flowers. Four methodologies were being used; Determination of pollination syndromes using floral characters, Determination of breeding systems using out crossing index, Estimation of breeding system by using pollen ovule ratio (P:O ratio) and by using Harmonic relation between pollinators and perianth shape and color. When looking at floral morphology, there may be several problems which can arise. •

The flower shape can not be exactly determined, as it depends on the observations. Also there can be more or less similar floral shapes.

•

In the case of determining odor, some can be determined an odor as pleasant, some can determine it as unpleasant, as it is subjective.

•

The nectar composition can not be simply determined.

•

Time can be either pollinator visitation time or time of the flowering.

23

Except the pollen ovule ratio method, all other methods can lead to erroneous conclusions, because they are subjective and therefore differ from person to person. For example, when considering the flower odor, it may be sensed differently by two individuals. Due to this reason, the results I obtained were found to be different compared to what was found in literature. Flower

Pollination syndrome

Pollination syndrome

Literature

according to

according to harmonic

cited

morphological

relation between the

pollination

characters

flower shape, color and the syndrome pollinator

Clitoria ternatea (Katarolu)

Ants

Syrphids, bees, butterflies

Butterflies

Cassia fistula (Ehela)

Butterflies

Bees

Butterflies

Nerium oleander (Kaneru)

Butterflies, birds

Moths, butterflies

Birds

Mirabilis jalapa (hendirikka)

Moth

Butterflies, moths

Moth

Sesbania grandiflora (Katurumurunga) Tecoma stans (Kelanithissa) Gardenia grandiflora (Gardenia)

Bee

Syrphids, bees, bats

Birds

Birds, ants

Flies, syrphids, bees, moths, Birds butterflies Beetles, flies, bees Bees

Cerbera manghas (Kaduru) Cesalpina pulcherrima (Monara mal) Camellia sinensis (Tea)

Moth, butterfly

Moths

Moths

Butterfly, birds

Butterflies

Butterflies

Bees, ants, butterflies,

Beetles, Flies, bees

Bees

Ants, beetles, flies, bees

beetles

24

According to the above comparison, the flowers of Clitoria ternatea employ ants as the pollination syndrome when determined by using morphological characters, Syrphids, bees and butterflies according to harmonic relation between the flower shape, color and the pollinator, but the literature says that Clitoria ternatea flowers are pollinated only by butterflies. Similarly, other flowers also behave more or less in the same manner. When we consider the results, some flowers have more than one pollination syndrome, whereas the others have only one each. The flowers that have more than one pollination syndrome are called generalized flowers and the flowers having only one pollination syndrome are called specialized flowers. The selection of flowers with suitable maturity is extremely important specially when determining the pollen ovule ratio. Either if the selected flower has already shed pollen or if the flower is not mature enough the counting of pollens is of less importance. Therefore, flowers with all pollen retaining inside must be selected. When determining breeding system by using outcrossing index, to check the stigma receptivity the stigma was dipped in a solution of hydrogen peroxide (H2O2); if air bubbles are formed, the stigma was considered to be receptive. Determining the temporal separation of male and female parts of the flower was also done under determining breeding system by using outcrossing index, but it requires experience and skill. According to the results obtained here all the flowers show some potential towards outbreeding. Outbreeding is the sexual reproduction between individuals whereas inbreeding is the sexual reproduction within an individual. There are some advantages and disadvantages of outbreeding and inbreeding: Advantages of outbreeding • • • •

Increases genetic variability Strong evolutionary potential Adaptation to changing conditions Successful long-term

Disadvantages of outbreeding • •

Can destroy well-adapted genotypes Relies on effective cross-pollination, and seed dispersal and establishment

25

Advantages of inbreeding • • • •

Preserves well-adapted genotypes Insures seed set in the absence of pollinators Overcomes sterility Single colonizing individual possible

Disadvantages of inbreeding • • • •

Decreases genetic variability Evolutionary dead-end Cannot adapt to changing environmental conditions Successful short-term

The results obtained from different methods suggest different breeding systems. For example, according to outcrossing index method Sesbania grandiflora is self compatible and has some demand for pollinators, but according to pollen ovule ratio method it is an obligate xenogamous flower. These mismatchings can be due to practical errors.

26

Conlusions •

Tubular, trumpet or bell shaped actinomorphic red, yellow or purple colored and nectar and nectar guide possessing flowers are pollinated by butterflies and birds.

•

Cream or white colored, fragrant, nectar containing nocturnal flowers are pollinated by moths.

•

Trumpet or bell shape zygomorphic or actinomorphic white, yellow or violet colored strong or mild pleasant odor, nectar and nectar guides’ present flowers are pollinated by bees.

•

Protogynous or protandrous flowers or flowers having spatially separated stigma and anthers and large flowers are cross pollinated.

27

References Holttum, R. E. and I. Enoch. 1991. Gardening in the Tropics. Times Editions Pte Ltd, Singapore. http://www.life.uiuc.edu (28/01/2009) http://www.fs.fed.us (29/01/2009) http://www.geocities.com (29/01/2009) http://en.wikipedia.org (29/01/2009)

28