Examples of this fascinating trait of fire-stimulated seed dispersal include Jack pine (Pinus banksiana, also called grey pine and scrub pine) in the north central and northeastern United States and Table Mountain pine (Pinus pungens, also called hickory pine, prickly pine or mountain pine) that grows in dry, rocky sites in the Appalachian. It bears seeds at a younger age than many associated arborescent oaks. In a study in West Virginia, acorn crops of blackjack oaks that averaged 0.87 inch (2.2 cm) d.b.h. Failed 2 out of 4 years. Dissemination is by gravity and animals. Germination is hypogeal. Blackjack oak grows more slowly than many associated trees, including post oak. How Are Blackjack Seeds Dispersed - 27466822 Which of the following statement is not correct a)free mind and free plane are mind mapping free and open educational software used for presenting ide.

Acacias are essentially insect pollinated; beetles, wasps and bees being mostly involved. Occasionally birds and mammals may be implicated (New 1984, Breeden & Breeden 1972, Knox et al. 1985) and although ants may be sometimes observed on the flowers they are probably not effective pollinators. However, there appear to be no specific pollinators and those that are involved are mostly generalists. For example, in a study (Bernhardt 1996) on bee pollination of acacias many native bees were observed to take Acacia pollen and also visit other flowers and carry their pollen, and presumably the pollen of other nearby flowering acacias. That there are relatively few Acacia hybrids suggests the existance of strong barriers to cross-pollination in Acacia. The European bee (Apis sp.), which collects pollen is now a common pollinator. Although the flowers lack nectar, many of the insects and some birds and aminals consume the pollen which is a rich source of protein. Insects, such as mites and thrips, feed on the flowers themselves, and some of the beetles and wasps appear to prey on these smaller insects, and may only incidentally serve as pollination vectors. Some honeyeaters have been cited by Ford & Forde (1976) as probably effecting pollination when visiting the nectaries (glands) of phyllodes near the inflorescences of Acacia pycnantha, either to take the nectar secretions or the insects associated with the secretions. In this case it was argued that the honeyeaters were more likely to facilitate outcrossing by visiting other nearby, as well as, more distant plants than would be the case with insects.

Acacia seeds are dispersed mostly by being ejected from the legume when it opens, usually under the influence of the hot sun. In some cases the seeds may remain hanging by their red or orange-coloured funicles from the open legume, the coloured funicle and aril acting as a bird attractant. The birds disperse the seed while its passage through the bird's gut may assist in germination. Emus and Mallee Fowl are also known Acacia seed dispersers.

Ants have been observed harvesting fallen seed. It is thought that the ants consume only the fleshy aril. This ant attracting structure, known as an elaiosome, is found in a large number of Australian xerophytic plants whose seeds are dispersed by ants. Such plants are known as myrmecochorous plants, and the benefits derived by such plants appears to be mainly in burying the seed and protecting it from predation rather than the actual removal of the seed further from the parent (Berg 1975). The soil covering will also protect the seed from the extreme temperatures of wildfires and possibly ensuring germination only after penetrating rain, although this is doubtful for deeply buried seed. Some seed, along with other detritus, may be deposited around the nest entrance, and this may provide a rich source of nutrients for germinating seedlings. See also Auld (1996).

Bidens pilosaL.

Bidens leucantha (L.) Willd.; Bidens sundaica (Blume)

Blackjack, Spanish needle, hairy beggar ticks, farmer's friend, cobbler's pegs, pitchforks, kichoma mguu (Kiswahili), labika (Acholi), muceege (Kikuyu), ononot (Lango)

Asteraceae (Compositae)

Native to tropical America

Bidens pilosa is naturalised throughout the tropics.

Bidens pilosa is invasive in parts of Kenya, Tanzania and Uganda (Global Invasive Species Database).

Bidens pilosa can invade roadsides, crops, pastures, gardens, disturbed areas, fallow lands and urban open space

Bidens pilosa is an annualherb with an erecthabit to 1.5 m in height (Stanley and Ross 1983-1989). It is easily recognised by the elongated fruits that bear hooked bristles (burrs) that embed themselves in people's clothing as they brush past the stems.

Stems are square in cross section (quadrangular), mostly hairless and green to purplish in colour. The leaves are oppositely arranged with leaf stalks (petioles) 1-6.5 cm long. Their margins have forward pointing teeth (serrated). Leaf blades vary in shape. At the base of the plant, leaves tend to be simple and more or less oval in shape, higher up the plant leaves are mostly compound (pinnate) with 3-7 egg-shaped with broad end at base (ovate) leaflets, and the uppermost leaves are smaller and simple or with 3 leaflets (trifoliolate). Leaf or leaflet size varies from 1.5-7 x 0.5-3.5 cm.

Flower-heads are 7-8 mm across with yellow central (tubular) florets. Some plants have flower-heads with white or cream 'petals' (rayflorets) up to 1.5 cm long, however these 'petals' may be absent or quite small. Heads are arranged in branched inflorescences at the ends of the branches. Flowering occurs over most of the year. The seeds are black, flattened, linear in shape (0.4-1.6 cm long) with a row of two to four barbedawns (2-4 mm long) at one end.

Bidens pilosa normally behaves as an annualweed but at least one form, B. pilosa var. radiata, may behave as a perennial. One isolated plant can produce over 30,000 seeds, which are generally highly viable. Seeds germinate on the soil surface or in shallow soil (to a depth of 1 cm). Seeds at greater depths remain viable in the soil for many years. There is usually a great flush of germination after tillage of the soil. Seeds are widely dispersed through the fruits hook-like bristles that embed themselves in clothing and the fur of mammals and feathers of birds. They are also spread by wind, water and soil.

The fresh or dried tender shoots and young leaves are eaten in some cultures, especially in times of food scarcity. It is used as a medicinal plant in many regions of Africa.

Bidens pilosa is a serious weed in many cropping systems in many countries where it reduces yield because of its fast growth and competitive abilities which include allelopathic properties. One study found that B. pilosa is a serious weed in many cropping systems in many countries where it reduces yield because of its fast growth and competitive abilities which include allelopathic properties. One study found that B. pilosa competition reduced dry bean, Phaseolus vulgaris harvests by 48% in Uganda. Bidens pilosa is also a host and vector to harmful parasites such as root knot nematodes (Meloidogynespecies) and tomato spotted wilt virus (GISD 2010). It is also a weed of open areas where dense stands reduce access to roads, trails, and recreational areas, and can damage pavements and walls. Its burrs are a nuisance to people, as well as to sheep and goats. The burrs are also a seed contaminant.

B. pilosa has been included in the Global Invasive Species Database (GISD 2010).

The precise management measures adopted for any plant invasion will depend upon factors such as the terrain, the cost and availability of labour, the severity of the infestation and the presence of other invasive species. Some components of an integrated management approach are introduced below.

The best form of invasive species management is prevention. As Bidens pilosa is so widespread this is unlikely to be possible in many instances.

If prevention is no longer possible, it is best to treat the weed infestations when they are small to prevent them from establishing (early detection and rapid response). Controlling the weed before it seeds will reduce future problems. Control is generally best applied to the least infested areas before dense infestations are tackled. Consistent follow-up work is required for sustainable management.

Bidens pilosa can be controlled by persistent mowing, hoeing and hand pulling in order to prevent seed production. Thorough cultivation discourages growth. Chemical control regimes depend upon the cropping system in which one is working. Details for individual crops can be found in the CABI Invasive Species Compendium. When using any herbicide always read the label first and follow all instructions and safety requirements. If in doubt consult an expert.

Biological control agents against B. pilosa are yet to be developed.

How Is Blackjack Seed Dispersal Method

Not listed as a noxious weed by the state or governments in Kenya, Tanzania and Uganda.

CABI invasive species compendium online data sheet. Bidens pilosa (blackjack). CABI Publishing 2011. www.cabi.org/ISC. Accessed March 2011.

GISD (2010). Global Invasive Species Database online data sheet. Bidens pilosa (herb) www.issg.org/database. Accessed March 2011.

How Is Blackjack Seed Dispersal Crops

Kleinschmidt, H.E., Holland, A. and Simpson, P. (1996). Suburban Weeds. 3rd Edition. Department of primary Industries, Brisbane.

Stanley, T.E. and Ross, E.M. (1983-1989). Flora of South-eastern Queensland. Volume 2. Department of Primary Industries, Brisbane.

Agnes Lusweti, National Museums of Kenya; Emily Wabuyele, National Museums of Kenya, Paul Ssegawa, Makerere University; John Mauremootoo, BioNET-INTERNATIONAL Secretariat - UK.

How Is Blackjack Seed Dispersal Fertilizer

This fact sheet is adapted from The Environmental Weeds of Australia by Sheldon Navie and Steve Adkins, Centre for Biological Information Technology, University of Queensland. We recognise the support from the National Museums of Kenya, Tropical Pesticides Research Institute (TPRI) - Tanzania and Makerere University, Uganda. This activity was undertaken as part of the BioNET-EAFRINET UVIMA Project (Taxonomy for Development in East Africa).

How Is Blackjack Seed Suited To Its Method Of Dispersal

BioNET-EAFRINET Regional Coordinator: eafrinet@africaonline.co.ke