Grevillea-Prac9

__ Group Members __ : Emily, Emily, Caitlin, Giulia, Maquel, Matteo

Pollination is the process by which the pollen of flowering plants is transferred to the stigma for fertilisation. Most flowering plants prefer cross-fertilisation as a way of increasing their genetic diversity and spreading their genes. This means that pollinators are needed to move the pollen from one plant to another. The flowers that are wind-pollinated are often dull in colour and odourless, as they do not need to attract any animals and can let the wind act as the pollinator. Plants with animals pollinators (birds, insects and other small mammals) often have brightly coloured and scented flowers. These pollinators search the flowers for a reward, such as a meal of nectar, and have pollen brushed on them by the flower. Different animals are attracted to different things on a flower and so plants have adapted to suit the pollinators of their choice. Bright red flowers, for example, are attractive to many bird species. This mutualistic interaction is favourable for both species involved. The plant’s pollen is spread to a variety of other plants, some of which may be far away, to fertilise another plant. The pollinators themselves get a reward of some kind, such as nectar.

Source: Knox, B., Ladiges, P., Evans, B., Saint, R 2011, //Biology – an Australian focus//, 4th edition, McGraw-Hill Company, NSW

__Plant species__: //Grevillea spp//. __Plant family__: Proteaceae __Common name__: Grevillea, spider flower, silky-oak and toothbrush __Distribution__: Native to Australia, New Guinea and New Caledonia. __Habit__: Range from small shrubs to large trees __Flowers__: Composed in small clusters, which may be more than 100 in some species. Can flower year round but the peak times are winter and early spring. __Inflorescence__: Arranged in 3 basic forms: spider-like, toothbrush-like and large brushes. __Fruit__: Are the thin-walled seed pods. These are shed once the seed has matured. __Seed__: Thin-walled seed pods, containing one or two seeds, appear after flowering. Once the seed inside is mature, these pods open and are distributed by wind.

Figure 1. Two common inflorescence types; (a) spider flower and (b) toothbrush inflorescence arrangement (Australia Native Plant Society, 2009)

Sources: // Plant profile: Grevillea // 2011, accessed 25 October 2012,  // Grevillea – background // 2009, accessed 25 October 2012, < http://anpsa.org.au/grev1a.html >

Figure 2. //Grevillea// inflorescence used for measurements.


 * Floral Morphology **

Figure 3. Grevillea flower with the labelled floral parts (note the epipetalous nature of the stamen).

Table 1. Floral measurements of 5 flowers collected using callipers; averages and standard deviations.
 * **Floral part** || **Average measurement (mm)** || **Standard Deviation** ||
 * Stigma + style length || 40.2 || 1.304 ||
 * Stigma width || 2.1 || 0.224 ||
 * Unfertilised/underdeveloped ovary length || 5.6 || 0.548 ||
 * Fertilised ovary length/width || 8.7/4.7 || 1.155 ||
 * Petal height (3-4 petals per floret) || 10.4 || 1.293 ||
 * Anther size || 1 || 0.000.. ||

Method: Flower were first carefully pulled off of the inflorescence stalk and then dissected in order to make measurements. The measurements of each of the floral parts was taken using callipers. 5 flowers from the same inflorescence were used.

Nectar was taken from the flower via a small glass 10 µ l capillary tube. Once enough had been collected it was placed on a refractometer and the sugar concentration recorded. Sugar concentration of nectar – 32% There was plenty of nectar in the flower but most of it was concentrated on the top half. This may have been where the flowers were newest and had yet to be taken by other pollinators. The older and shrivelled looing inflorescence on the bottom of the flower had less nectar available, if any at all. It may have already been taken from the glower before it was picked for this lab.
 * ‍ **** Nectar information **

Figure 5. Pollen from the Grevillea under a light microscope at 100x objective.
 * ‍Pollen information **

The pollen grains of this flower are triangular in shape with rounded bulges at each corner. It is thought this may be where the pollen tube extends from once it comes in contact with the stigma. There were plenty of pollen grains in this one sample. It is thought that the number of pollen grains would be the same on the anthers of the entire flower.