ArtsAutosBooksBusinessEducationEntertainmentFamilyFashionFoodGamesGenderHealthHolidaysHomeHubPagesPersonal FinancePetsPoliticsReligionSportsTechnologyTravel

plants have Sex- only in ANGIOSPERMS?

Updated on July 29, 2015

Keywords:

Sexual Reproduction. Flowers. Pollination. Angiosperms. Herkogamy. Chasmogamy. Apomixis. Asexual reproduction.

     Pollen Tube from a Germinating Pollen Grain
Pollen Tube from a Germinating Pollen Grain
             Quote from Desmond Tutu
Quote from Desmond Tutu

Introduction

That man could not live without plants. By providing foods. shelter, clothing and industry are the keys to the continued existence of man. Though presently there are plant species that could not exist in the wild without the intervention of man, nevertheless, plants form the basic of human needs. But, why some plants are more successful in exploring different ecological niche while others are not. All organism micro or macro must have undergone sexual reproduction at one time in their lifecycle in order to drive the engine of evolution. Otherwise, if one can not leave viable offspring in the next generation they are doomed to extinction. Sexual reproduction brings reshuffling of genes that may have a selective advantage thus, ensuring the survival of the species every generation.

                             Rise of Angiosperms
Rise of Angiosperms
       Major groups of plants by Ecological Era
Major groups of plants by Ecological Era

Rise of Angiosperms

The exact lineage of angiosperms or flowering plants is difficult to established. Archeological evidence shows that plants started to dominate the terrestrial world 500 million years ago (mya), moreover, the rise of angiosperms was only noted in the later Mesozoic era, 150 million years ago(mya), furthermore, the ancient progenitor of angiosperms was never found. Today, angiosperms are the most successful and diverse among land plants. Phylogenetically, angiosperms belong to a large group of plants, the Phylum Anthophyta or flowering plants. The 250,000 known species is further divided into Class.Dicotyledoneae (the Dicots) and Class Monocotyledoneae ( the Monocots). The dicots are more numerous than the monocots.

    Types of POLLEN grains- Beware pollen ALLERgy
Types of POLLEN grains- Beware pollen ALLERgy
           Key insect pollinators of plants=the 3Bs'
Key insect pollinators of plants=the 3Bs'
Pollen grains in the pollen basket of a bee
Pollen grains in the pollen basket of a bee

Another major event during this period that coincide with the rise of angiosperms is the appearance of insects. It was believed that the success of angiosperms as land plants could be largely attributed to the co-existence with insects. As pollinators, insects is rewarded with foods (honey, nectar, pollen, etc.) and a place to live, consequently, the plants get pollinated, produced seeds thus, ensuring species continuity for generations to come. The seeds, a product of the sexual union is now the biological currency of evolution. There are three big groups of insects from 950,000 known species, namely Butterflies and moths (Lepidoptera), Flies (Diptera), and Bees and wasps (Hymenoptera) are the major pollinators of angiosperms or flowering plants.

CHOCOLATE hills from Bohol- Nature's Natural Recipe?
CHOCOLATE hills from Bohol- Nature's Natural Recipe?
           Chandeliers plant- Aristolochia
Chandeliers plant- Aristolochia
Generalized Life CYcle of Angiosperms
Generalized Life CYcle of Angiosperms
       Insects as agents of Pollenation
Insects as agents of Pollenation
                     Double Fertilization
Double Fertilization

life cycle of Angiosperms

From birth to death, in plants it begins from the Flower. In all living flowering plants, the flower is the basic unit of reproduction. The coming together of sperm and egg during fertilization, the biological union of male and female gametes signals the birth of a new individual complete with genetic information to find an ecological niche among the living.

The angiosperms or flowering plants are unique among earth's living inhabitants, being immobile, yet was able to colonize every habitable area of the world. What is its secret? these group of plants exhibits double fertilization.

During fertilization brought about by pollination, the generative nucleus inside the pollen tube divide once more to produce two haploid (n) nuclei. The pollen tube penetrates the embryo sac (deflowering?).The embryo sac is eight nucleate cells derived from the placental walls of the ovule, composed of three antipodals, two polar, two synergids(egg apparatus and one egg. Double fertilization emanates from: One sperm unites with an egg=zygote(2n), one sperm unites with two polar nuclei=endosperm(3n). Nature is very intelligent, the zygote(2n) is a diploid individual ensuring the constancy of chromosome number of the species while the endosperm(3n), a triploid whose main function is to store food, being a bigger cell, can accommodate large volume of food for the embryo (miniature plant) once detached or dispersed from the mother plant. Thus, this food provisioning ensures the survival of the species from generation to generation. Plants have sex, double fertilization, this is the secret of angiosperms or flowering plants. Most of the foods derived from plants are endosperm, the three great bowls of cereal namely, rice, wheat, and corn have a very small embryo but large eatable endosperms. These three bowls of cereal supply 60 percent of the calorie requirements of man.

Hermaphrodite plant ( Perfect flower)
Hermaphrodite plant ( Perfect flower)
 Morphological Differences between Monocot        and Dicot plants
Morphological Differences between Monocot and Dicot plants

Flowering plants-Monocots and Dicots

The angiosperms or flowering plants were further divided into two big groups, the Dicot class and the Monocot class. Morphological differences between these two classes are shown below. The monocots comprising about 65,000 species and the Dicots, 175,000 species. The Dicots are more primitive of the two classes with monocots apparently having derived from early dicots. Included in the dicots are the great majority of familiar angiosperms, almost all kinds of trees, shrubs, mints, peas, sunflower and other plants. Monocots include the lilies, grasses, palms, agaves, orchids, irises among others and the great three bowls of cereal: rice, corn and wheat.

Take a Quiz

Match Column A with B. Letters ONLY

Column A Column B

  1. Complete flower a) pollen shed before stigma receptive
  2. Pistillate flower b) temporal separation of male and female flowers
  3. Staminate flower c) flower opens before pollination
  4. Perfect flower d)four essential parts
  5. Monoecious e) female structure only
  6. Dioecious f) flower opens after pollination
  7. Cleistogamy g) staminate and pistillate flowers borne in different plants
  8. Chasmogamy h) male structures only
  9. Dichogamy i) bears male and female organs
  10. Protandry j) bears staminate and pistillate flowers

SCORE:

Excellent= 10, Very Good= 8-9, Good= 6-7, Average= 5

The Ring of TRUTH, more questions to be ANSWERED and answers to be QUESTIONED?
The Ring of TRUTH, more questions to be ANSWERED and answers to be QUESTIONED?
 Dust of Pollen grains from  Grass anthers-Monocot
Dust of Pollen grains from Grass anthers-Monocot
Granular Pollen grains from Hibiscus anthers-Dicot
Granular Pollen grains from Hibiscus anthers-Dicot

Flowers-the center of attraction

  • In higher plants, the flower is the fundamental unit for sexual reproduction. There are four essential parts of a flower, namely,
  • Petals- collectively called Corolla
  • Sepals- collectively called Calyx
  • Stamen-the male gametophyte(Pollen grains, Anthers, Filament)
  • Pistil- the female gametophyte(Stigma, Style, Ovary)

A complete flower, therefore, is composed of four essential parts. Variation in floral structures arose if one of these essential parts is missing. For instance, a flower is called Incomplete when one of these essential is missing. If the male and female structure is present on the same flower, it is called Perfect flower, but if both male and female structures are separated, they are called Imperfect flowers. Imperfect flowers could be either, Staminate(male) or Pistillate(female) flowers respectively.


A single STIGMA and several ANTHERS- a Perfect Flower
A single STIGMA and several ANTHERS- a Perfect Flower

reproduction in the Angiosperms

Plant production is the real basis for agriculture. Human beings has been taking advantage of all plant reproductive processes- both sexual and asexual, In the most general terms, reproduction is the total sequence of events required for the replication of cells and the organisms.

Richardson and Stubbs, 1977

Staminate dominance-Showy Anthers-more attractive than petals?
Staminate dominance-Showy Anthers-more attractive than petals?

Do you Know?

that Ismail, the Blood Thirsty (Sultan of Morocco, 1672-1727)

is reported to have fathered 888 offsprings during his reign?

SUFFERED Inversion?-that's what you get for being a pilot at NASA!
SUFFERED Inversion?-that's what you get for being a pilot at NASA!
The Difference between male(Staminate) and female(Pistillate) flowers of Cannabis Plant
The Difference between male(Staminate) and female(Pistillate) flowers of Cannabis Plant
             Essential parts of a FLOWER
Essential parts of a FLOWER

sexual Reproduction in Angiosperms

There are two kinds of reproduction employed by flowering plants, that is, asexual and sexual reproduction respectively. The former is based on somatic propagation while the later is based on the modes of pollinations. We will be focusing our discussion on sexual reproduction. Pollination is an important strategy in sexual reproduction, there are two types of pollination, namely self and cross-pollination. The less technical definition says that. the transfer of pollen grains from the anthers to the stigma of the same flower is called self-pollination while the transfer of the pollen grains from the anthers to the stigma of another flower is called cross-pollination. Self-pollination or selfing is the most drastic form of inbreeding, that is the mating of closely related individuals that lead to homozygosity. Experts believed that selfing is the end of an evolutionary path. Cross-pollination allows reshuffling of genes that may possessed evolutionary adaptive environmental fitness compared with inbreeders.

The meaning of sex here is not the erotic one but rather a function to effect the union of male and female gametes in the process of sexual reproduction. Sex remains an enigma within a mystery. It is baffling for the reason other than the fact that, in atypical and isogamous species with no male investment in young, a female could have as many grandchildren were she an asexual (apomict). From various definition of sex, two broad categories tend to predominate, that is, a) that sex enables the spread /creation of advantageous traits and b) that sex enables the efficient removal of deleterious genes. Simply sex is defined as putting together genes from two different individuals into one and producing recombinant genotypes. these new gene combinations could be an important asset for the survival of the species.

Sexual Types

one sexual type
percent
 
hermaphroditism
72
 
monoecy
5
 
andromonoecy
1.7
 
gynomonoecy
2.8
 
two sexual type
 
 
dioecy
4
 
gynodioecy
7
 
androdioecy
rare
 
Source: Jarne 1993

Plant sex, Flower sex and others

Because of the diversity of floral structures brought about by adapted evolutionary changes through time, some plants are classified as Monoecious(one house) when both male and female structures are both found on the same plant or same flower (hermaphrodite), the hermaphrodites are more numerous, accounting 72% of all sexual types. Moreover, if male and female structures are on separate plants are called Dioecious (two houses), male and female plants exist, examples of this condition are: papaya(Carica papaya), while monoecious plants include rice, corn, and wheat. Plants which bears female flowers only are called Pistillate, while plants that have male flowers only are Staminate, therefore, it is not uncommon to find different sexual types co-exist with one another.

According to Barrett and Harder(1996), sex in flowering plants is complicated by three distinct features of their biology:

  • First, being sessile, plants requires vectors to transfer male gametes(pollen) between individuals. Animals are most commonly employed as pollinators because of their flexibility that can be manipulated by plant traits.
  • Second, most plants are hermaphrodite (male and female structures present), so, are capable of selfing sometimes at the expense of outcrossing.
  • Third, owing to their modular construction of plants, male and female gametes are packed in bewildering array of their structural and temporal combinations at the flower, inflorescence, plant or population level and despite the hermaphroditic condition.

Because of vector-mediated transfer and elaborate sexual system, plant mating can be highly "promiscuous" with individuals mating with many sexual partners including themselves.

POllen GRAINs from the anther of Geranium
POllen GRAINs from the anther of Geranium
I am too sluggies to fly, my belly is full of SODA!
I am too sluggies to fly, my belly is full of SODA!

types of Mating sYSTEMS

The primary mating system in plants are, outcrossing(cross-pollination), autogamy(self-pollination) and apomixis (asexual reproduction without fertilization). Likewise, in a mixed mating system. plants use two or even more three mating systems are not uncommon. A mating system is a way in which a group is structured in relation to sexual behavior. The precise meaning depends on the context. In plants, the term refers to the degree and circumstances that promote cross- pollination (Wikipedia, the free Encyclopedia).Flowering plants are predominantly hermaphroditic with most species producing flowers that contain both a female (pistil) and a male(stamen) sexual organs. These sexual structures can be separated spatially in a flower (Herkogamy) or can function at different times (Dichogamy), reducing the likelihood of self-pollination. In Apomixis, sexual organs or related structures take part but no union of gametes(reproductive cells), thus no fertilization occurs. The resulting seed is vegetatively produced. although there is no union of gametes, pollination is necessary to initiate the development of the endosperm. Forms of apomixis include the following:

  • Parthenocarpy-is the phenomenon wherein fruits develop even without pollination, thus no seeds are formed..
  • Apogamy-is the development of the embryo from haploid nuclei other than the egg. Generally, apogamy results from the fusion of two cells of the embryo sac.
  • Apospory-is the formation of the embryo sac directly from a somatic cell without reduction and formation of spores.

mechanisms or devices of Pollination Control

Devices for the control of the mating system, whether to encourage inbreeding or outbreeding, are present in different ways in higher plant species and these are:

  • Cleistogamy-stigma pollinated before the flower opens, favors self-pollination. Example-lettuce, annual fescue, several rice varieties.
  • Chasmogamy-stigma pollinated after the flower opens, favors cross-pollination. Example-tomato
  • Dichogamy-temporal maturity of male and female structure favors cross-pollination. Example-corn
  • a) Protandry-pollen dehisced before stigma becomes receptive. Example-carrots. soybeans
  • b)Protogyny-stigma receptive before pollen is dehisced. Example-avocado, walnut
  • Monoecious-staminate(male)and pistillate(female) flowers are borne on the same plant favors self-pollination. Example-rice,
  • Dioecious-staminate and pistillate flowers are borne on separate plants favors cross-pollination. Example-papaya, durian, rambutan

                  Incompatibility System in Higher plants
Incompatibility System in Higher plants

Mechanism of Self-incompatibility in flowering plants

Self-incompatibility mechanisms are designed to prevent self-pollination. Experts believed that inbreeding is the end of the evolutionary path. There are two general types of self-incompatibility in higher plants, namely;

  • a) Gametophytic- the reaction is determined by pollen genotype. Stylar Inhibition.
  • b) Sporophytic- the reaction is determined by sporophyte genotype.Stigmatic Inhibition
  • Similar genotypes preclude self-pollination(see figure).

PETALS used as Landing Platform for Pollinators?
PETALS used as Landing Platform for Pollinators?
           I'm a BIRD, I'm a FLY! WHO am I?
I'm a BIRD, I'm a FLY! WHO am I?
Both male (upper side) and female (lower side) flower present-MONOECIOUS?
Both male (upper side) and female (lower side) flower present-MONOECIOUS?
              The lament of Dandelion-an Apomict (practice Asexual reproduction) ONLY in flowering PLANTS
The lament of Dandelion-an Apomict (practice Asexual reproduction) ONLY in flowering PLANTS

Ode to an Apomict: THE DANDELION

Daughters I have many

Yet husband and father none

A perfect matriarchy

I set in the sun

And send my plumed children

Floting one by one

conclusion

Sexual reproduction is important for the continued existence of the species. It serves as the vehicle for evolution to operate in the development and survival of the species, whether plants or animals. The investment in sex may be measured quantitatively in terms of new gene combinations brought about by the union of gametes and the frequency of this new genotypes in the sexually interbreeding population. Individuals that cannot transmit their genetic endowment to the next generation may become extinct and the demise of the population. The question of "promiscuity" in plants is of no consequence, the flowers as sexual organs are will structure designed for either, self and cross pollination that may accept gametes from different sexual partners, including themselves.

   Sipping sugary Nectar- Don't get DRUNK!
Sipping sugary Nectar- Don't get DRUNK!

Glossary

Chasmogamy-pollination event happened in an opened flower

Dicots-are plants under the Class Dicotyledoneae of sub-Phylum Angiospermae or flowering plants, many known plants belong to this group, trees shrubs, food crops, etc.

Dioecy - a sexual polymorphism in which population contain male and female plants

Evolution- a change in gene frequency over time

Flower- a modified shoot designed for sexual reproduction

Herkogamy- spatial separation of sexual structures in a flower

Hermaphrodite- individual that can be male or female, occurrence may be sequential or simultaneous

Isogamy-is a form of sexual reproduction that involves gametes of similar morphology( similar in shape and size) differing only in the expression of alleles in the population.

Monocots-are plants that belong to Class Monocotyledoneae sub- Phylum Angiospermae or flowering plants include the tallest grass of the world-Bamboo and the three great bowls of cereals, namely, rice, corn, and wheat.

Sex -refers to the union(syngamy) of gametes, individuals need not have distinct sexes attributed to differences in size or structure of gametes


 Super Killers - Father and Son- Dad let's HUNT!
Super Killers - Father and Son- Dad let's HUNT!

References

SCHOLARLY ARTICLES:

Barnett, Spencer. 2002. The evolution of plant sexual diversity(a Review).Genetics 3: 274-284.

Cresti, M and A. Trezzi (eds.) Sexual reproduction in plants.pp.48-88.Springer-Verlag.

Faure, J.2001. Double fertilization in flowering plants: discovery, study methods, and mechanism. CNR Acad. Sci.Vol.3.

Hartfield, M and P, Keightley.2012. The current hypothesis for the evolution of sex and recombination. Integrative Zoology 7:192-209.

Ward, J. et al.2014.Variation in sex allocation and floral morphology in an expanding distylous plant hybrids.International J. of Plant Sciences.175(5): 518-525.

Handouts on Evolutionary Biology, Plant Breeding, and Botany

INTERNET sources:

www.britanica.com

www.encyclopedia.com

www.flekr.com

www.nationalgeogrphic.com

www.nature.com

www.scincedaily.com

www.wayne's word.palomar.edu

www.wileyonline.library

www.wikipedia.com

www.wikimedia.com


                  The Headhunters of Tribu Agotaya
The Headhunters of Tribu Agotaya

Comments

    0 of 8192 characters used
    Post Comment

    No comments yet.

    working

    This website uses cookies

    As a user in the EEA, your approval is needed on a few things. To provide a better website experience, hubpages.com uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

    For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at: https://hubpages.com/privacy-policy#gdpr

    Show Details
    Necessary
    HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
    LoginThis is necessary to sign in to the HubPages Service.
    Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
    AkismetThis is used to detect comment spam. (Privacy Policy)
    HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
    HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
    Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
    CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
    Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the googleapis.com or gstatic.com domains, for performance and efficiency reasons. (Privacy Policy)
    Features
    Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
    Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
    Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
    Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
    Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
    VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
    PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
    Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
    MavenThis supports the Maven widget and search functionality. (Privacy Policy)
    Marketing
    Google AdSenseThis is an ad network. (Privacy Policy)
    Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
    Index ExchangeThis is an ad network. (Privacy Policy)
    SovrnThis is an ad network. (Privacy Policy)
    Facebook AdsThis is an ad network. (Privacy Policy)
    Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
    AppNexusThis is an ad network. (Privacy Policy)
    OpenxThis is an ad network. (Privacy Policy)
    Rubicon ProjectThis is an ad network. (Privacy Policy)
    TripleLiftThis is an ad network. (Privacy Policy)
    Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
    Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
    Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
    Statistics
    Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
    ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
    Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)