Algae, Tree, Herbs, Bush, Shrub, Grasses, Vines, Fern, Moss, Spermatophyta, Bryophyta, Fern Ally, Flower, Photosynthesis, Eukaryote, Prokaryote, carbohydrate, vitamins, amino acids, botany, lipids, proteins, cell, cell wall, biotechnology, metabolities, enzymes, agriculture, horticulture, agronomy, bryology, plaleobotany, phytochemistry, enthnobotany, anatomy, ecology, plant breeding, ecology, genetics, chlorophyll, chloroplast, gymnosperms, sporophytes, spores, seed, pollination, pollen, agriculture, horticulture, taxanomy, fungi, molecular biology, biochemistry, bioinfomatics, microbiology, fertilizers, insecticides, pesticides, herbicides, plant growth regulators, medicinal plants, herbal medicines, chemistry, cytogenetics, bryology, ethnobotany, plant pathology, methodolgy, research institutes, scientific journals, companies, farmer, scientists, plant nutrition
Select Language:
 
 
 
 
Main Menu
Please click the main subject to get the list of sub-categories
 
Services offered
 
 
 
 
  Section: Principles of Horticulture » Plant reproduction
 
 
Please share with your friends:  
 
 

Flowers

 
     
 
Content
Plant reproduction
  Flowers
  The seed
  The fruiting plant
  Reproduction in simple multicellular green plants

Types of inflorescence
Euphorbia cyparissias ‘Fens Ruby
Figure 7.1 Euphorbia
cyparissias
‘Fens Ruby’
The organs of sexual reproduction in the flowering plant division are flowers, and variation in their arrangement can be identified and named:
Range of flowers as organs of sexual reproduction having similar basic structure, but varying appearance having adapted for
Figure 7.2 Range of flowers as organs of sexual reproduction
having similar basic structure, but varying appearance having
adapted for successful pollination or by plant breeding (see
Pollination & Fertilization) (a) Iris chrysographes ‘Kew Black’; (b)
Eryngium giganteum, (‘Miss Willmott’s ghost’); (c) Trollius
chinensis
‘Golden Queen’; (d) Rosa ‘L.D.Braithwaite’;
(e) Hemerocallis Rajah’; (f) Aquilegia fragrans; (g) Oenothera
‘Apricot Delight; (h) Helenium ‘Wyndley’; (i) Helleborus
xhybridus;
(j) Nepeta nervosa; (k) Primula vialii

  • spike is an individual, unstalked series of flowers on a single flower stalk, e.g. Verbascum;
  • raceme consists of individual stalked flowers, the stalks all the same length again spaced out on a single undivided main flower stalk, e.g. foxglove (see Figure 7.3), hyacinth, lupin, wallflower;
  • compound racemes have a number of simple racemes arranged in sequence on the flower stalk, e.g. grasses;
  • corymb is similar to a raceme except that the flower stalks, although spaced out along the main stalk, are of different lengths so that the flowers are all at the same level, e.g. Achillea (see Figure 7.3). A very common sight in hedgerows;
  • umbel has stalked flowers reaching the same height with the stalks seeming to start at the same point on the main stem, e.g. hogweed (see Figure 7.3);
  • capitulum or composite flower forms a disc carrying flower parts radiating out from the centre, as if compressed from above, e.g. Inula (see Figure 7.3), daisy, chrysanthemum.
The number and arrangement of flower parts are the most important features for classification and are a primary feature in plant identification (see Classification and naming).
Figure 7.3 Inflorescence types, (a) spike;
Verbascum (b) raceme; Foxglove and (c)
Veronica; (d) corymb, Achillea; (e) umbel,
Hogweed; (f) capitulum, Inula


Flower structure
The flower structure is shown in Figure 7.4.

The flower is initially protected inside a flower bud by the calyx or ring of sepals, which are often green and can therefore photosynthesize. The development of the flower parts requires large energy expenditure by the plant, and therefore vegetative activities decrease. The corolla or ring of petals may be small and insignificant in wind-pollinated flowers, e.g. grasses, or large and colourful in insect-pollinated species. The colour and size of petals can be improved in cultivated plants by breeding, and may also involve the multiplication of the petals or petalody, when fewer male organs are produced.

The flower may include other parts:
  • Tepals, where the outer layers of the flower have a similar appearance, making the sepals and petals indistinguishable. They are common in monocotyledons such as tulips (see Figure 7.5) and lilies.
  • Androecium, the male organ, consists of a stamen which bears an anther that produces and discharges the pollen grains.
  • Gynaecium, the female organ, is positioned in the centre of the flower and consists of an ovary containing one or more ovules (egg cells). The style leads from the ovary to a stigma at its top where pollen is captured.
  • The flower parts are positioned on the receptacle, which is at the tip of the pedicel (flower stalk).
  • Nectaries may develop on the receptacle, at the base of the petals; these have a secretory function, producing substances such as nectar which attract pollinating organisms.
  • Associated with the flower head or inflorescence are leaf-like structures called bracts, which can sometimes assume the function of insect attraction, e.g. in Poinsettia.
The flowers of many species have both male and female organs (hermaphrodite), but some have separate male and female flowers (monoecious), e.g. Cucurbita, walnut, birch (Betula), whereas others produce male and female flowers on different plants (dioecious), e.g. holly, willows, Skimmia japonica and Ginkgo biloba.

Glaucium corniculatum
Figure 7.4 Flower structure, e.g. (a) flower of Glaucium corniculatum and
(b) diagram of typical flower to show structures involved in the process of
sexual reproduction.
Figure 7.5 Tulip ‘Attila’,
e.g. of tepals – outer
layers of flower are
similar
 
     
 
 
     



     
 
Copyrights 2012 © Biocyclopedia.com | Disclaimer