Seed Dispersal / Fruit Dispersal

Plants disperse their seeds away from them so as to increase their chance of survival.

When seeds are dispersed near the parent plants, they will most probably germinate into young seedlings.

However, these young seedlings would then have to compete for four factors, namely :

1. water

2. nutrients

3. light and

4. space

This is so because, at the first stage of germination, when it is just a seed, it only requires Water,

Oxygen and

Warmth (or right temperature).

The seed at this stage obtains its food from the seed leaves.

At the second stage, when the first root appears, it requires

Water,

Oxygen,

Warmth (or right temperature) and

Edaphic (soil conditions which include porous soil and presence of humus).

At the final stage of germination, before it becomes an adult plant, it requires

Water,

Oxygen,

Warmth (or right temperature),

Light and

Edaphic (soil conditions which includes porous soil and presence of humus).

It is quite easy to notice certain features found in the seeds/fruits of a plant which help them to be dispersed.

(A) Seeds that are dispersed by wind have the following characteristics :

1. light

This allows the seeds to be carried in the air for a longer time before they

land on the ground. Seeds that are light are usually dispersed far away

from their parent plants and thus this increases their chance of survival.

Eg : Vernonia

→

Flowers Seeds are light and can be

blown away by wind

2. have wing-like structures

These wing-like structures or ‘wings’ enable the seeds to be carried further

away from their parent plants.

Eg. Angsana

(B) Seeds dispersed by water have certain characteristics.

1. They usually have fibrous husks. These fibrous husks have air

spaces in them that help them stay buoyant (able to float).

2. They must also be waterproof to stay buoyant.

Eg : Coconut

Fibrous husk

Eg ; Nipah

(C) Seeds that are dispersed by animals have the following

characteristics :

1. They are usually fleshy, sweet and colourful. These features help

them to attract animals to feed on them. The seeds are usually very

hardly and will not be harmed by the digestive juices of the

animals’ stomach. These seeds will then be passed out together

with their droppings.

2. Some fruits and seeds are not brightly coloured, sweet and fleshy. They

have some structures to help them :

- hook-like structures to attach to the clothes of humans or fur of animals

When noticed, these seeds will be pulled out from the clothes or fur and disposed off further away from their plant plants. When they fall on good soil and when the conditions are right, they will germinate into seedlings.

Eg. mimosa fruits

Fruit of mimosa with stiff hair

(D) Some fruits and seeds are dispersed by explosive action

(or splitting)

These fruits are usually in the form of a pod.

A pod-like fruit has certain lines on them.

These are the places where the fruit split open.

Eg. Rubber fruits and lady’s finger

Notice the lines.

This pod-like fruit

splits open when

dry.

Rubber fruit and seeds

Notice

the lines

Lady’s finger

(E) Some fruits and seeds are dispersed using more than one method.

Eg. African Tulip

A bird feeding on the nectar of the

flower and at the same time helping

to pollinate the pollen grains.

The fruit pod of the African Tulip

The fruit splits open and creates a force to

throw out the seeds.

The wing-like structure

enables the seed to be

carried away by wind.

Hence, the African Tulip fruit splits open and throws out the seeds at first.

The wing-like structure enables the seeds to be carried away by wind.

Always remember that an organism reproduces to ensure the continuity of its own kind.

PINEAPPLE

Ananas comosus

Bromeliaceae

Common Names: Pineapple, Ananas, Nanas, Pina.

Related Species: Pina de Playon (Ananas bracteatus).

Distant affinity: Pingwing (Aechmea magdalenae), Pinguin (Bromelia pinguin), Pinuela (Karatas plumier).

Origin: The pineapple is native to southern Brazil and Paraguay where wild relatives occur. It was spread by the Indians up through South and Central America to the West Indies before Columbus arrived. In 1493 Columbus found the fruit on the island of Guadaloupe and carried it back to Spain and it was spread around the world on sailing ships that carried it for protection against scurvy. The Spanish introduced it into the Philippines and may have taken it to Hawaii and Guam early in the 16th Century. The pineapple reached England in 1660 and began to be grown in greenhouses for its fruit around 1720.

Adaptation: The pineapples is a tropical or near-tropical plant, but will usually tolerate brief exposures to 28° F. Prolonged cold above freezing retards growth, delays maturity and causes the fruit to be more acid. Pineapples are drought-tolerant and will produce fruit under yearly precipitation rates ranging from 25 - 150 in., depending on cultivar and location and degree of atmospheric humidity. They are successfully grown in southern Florida and coastal areas of southern California. The small plant adapts well to container and greenhouse culture and makes an interesting potted plant.

DESCRIPTION

Growth Habit: The pineapple plant is a herbaceous perennial, 2-1/2 to 5 ft. high with a spread of 3 to 4 ft. It is essentially a short, stout stem with a rosette of waxy, straplike leaves.

Foliage: The long-pointed leaves are 20 - 72 in. in length, usually needle tipped and generally bearing sharp, upcurved spines on the margins. They may be all green or variously striped with red, yellow or ivory down the middle or near the margins. As the stem continues to grow, it acquires at its apex a compact tuft of stiff, short leaves called the crown or top. Occasionally a plant may bear 2 or more heads instead of the normal one.

Flowers: At blooming time, the stem elongates and enlarges near the apex and puts forth an inflorescence of small purple or red flowers. The flowers are pollinated by humming-birds, and these flowers usually develop small, hard seeds. Seeds are generally not found in commercially grown pineapple.

Fruit: The oval to cylindrical-shaped, compound fruit develops from many small fruits fused together. It is both juicy and fleshy with the stem serving as the fibrous core. The tough, waxy rind may be dark green, yellow, orange-yellow or reddish when the fruit is ripe. The flesh ranges from nearly white to yellow. In size the fruits are up to 12 in. long and weigh 1 to 10 pounds or more.

CULTURE

Location: Pineapples should be planted where the temperature remains warmest, such as the south side of a home, or in a sunny portion of the garden.

Soil: The best soil for the pineapple is a friable, well-drained sandy loam with a high organic content. The pH should be within a range of 4.5 to 6.5. Soils that are not sufficiently acid can be treated with sulfur to achieve the desired level. The plant cannot stand waterlogging and if there is an impervious subsoil, drainage needs to be improved.

Irrigation: The plant is surprisingly drought tolerant, but adequate soil moisture is necessary for good fruit production.

Fertilization: Nitrogen is essential to increase fruit size and total yield, which should be added every four months. Spraying with a urea solution is another way to supply nitrogen. Fruit weight has also been increased by the addition of magnesium. Of the minor elements, iron is the most important, particularly in high pH soils. Iron may be supplied by foliar sprays of ferrous sulfate.

Frost Protection: Pineapple plants require a frost-free environment. They are small enough to be easily covered when frost threatens, but cold weather adversely affects the fruit quality.

Propagation: Pineapples are propagated by new vegetative growth. There are four general types: slips that arise from the stalk below the fruit, suckers that originate at the axils or leaves, crowns that grow from the top of the fruits, and ratoons that come out from the under-ground portions of the stems.

Although slips and suckers are preferred, crowns are the main planting material of home gardeners. These are obtained from store-bought fruit and are removed from the fruit by twisting the crown until it comes free. Although the crown may be quartered to produce four slips, in California's marginal conditions it is best not to cut or divide the crown. The bottom leaves are removed and the crown is left to dry for two days, then planted or started in water.

Pineapples are planted outside during the summer months. A ground cover of black plastic works very well for pineapples, both as protection from weeds and for the extra heat it seems to absorb. It also helps to conserve moisture. Traditionally, plants are spaced 12 inches apart. Set crowns about 2 inches deep; suckers and slips 3 to 4 inches deep.

Pests and diseases: Mealybugs spread by ants can be a problem. Controling the ants will control the mealybugs. In most commercial growing areas, nematodes, mites and beetles can also be damaging, but these have not been a problem in California.

Harvest: It is difficult to tell when the pineapple is ready to be harvested. Some people judge ripeness and quality by snapping a finger against the side of the fruit. A good, ripe fruit has a dull, solid sound. Immaturity and poor quality are indicated by a hollow thud. The fruit should be stored at 45° F or above, but should be stored for no longer than 4 - 6 weeks.

Misc.: Fruiting can be forced when the plant is mature by using acetylene gas or a spray of calcium carbide solution (30 gms to 1 gal. water), which produces acetylene. Or calcium carbide (10 -12 grains) can be deposited in the crown of the plant to be dissolved by rain. A safer and more practical method for home growers is a foliar spray of a-naphthaleneacetic acid (1 gm in 10 gal water) or B-hydroxyethyl hydrazine. The latter is more effective. The plants usually produce for about four years, but they may last longer in California since the life cycle is slowed down by cooler weather.

CULTIVARS

Hilo

A compact 2-3 lb. Hawaiian variant of the Smooth Cayenne. The fruit is more cylindrical and produces many suckers but no slips.

Kona Sugarloaf

5-6 lbs, white flesh with no woodiness in the center. Cylindrical in shape, it has a high sugar content but no acid. An incredibly delicious fruit.

Natal Queen

2-3 lbs, golden yellow flesh, crisp texture and delicate mild flavor. Well adapted to fresh consumption. Keeps well after ripening. Leaves spiny.

Pernambuco (Eleuthera)

2-4 lbs with pale yellow to white flesh. Sweet, melting and excellent for eating fresh. Poorly adapted for shipping. Leaves spiny.

Red Spanish

2-4 lbs, pale yellow flesh with pleasant aroma; squarish in shape. Well adapted for shipping as fresh fruit to distant markets. Leaves spiny.

Smooth Cayenne

5-6 lbs, pale yellow to yellow flesh. Cylindrical in shape and with high sugar and acid content. Well adapted to canning and processing. Leaves without spines. This is the variety from Hawaii, and the most easily obtainable in U. S. grocery stores.

Hi Everyone,

I am very glad that I was able to send out the two earlier sets of mail.

In today's lesson, I asked you to find out more about a pineapple.

Is it a fruit?

If it is, then, is it a true or false fruit?

Well, I have attached together with this mail an abtract for your reading pleasure.

Please try searching for information using the search engine first before opening the attachment.

Happy investigation and reading.

We shall be completing our study on the Reproduction of Plants by Tuesday and beginning our study on Reproduction of Humans.

Prior to this, I shall be introducing the idea of a fair test and how it is different from a control experiment.

Please look at Activity 2.5 to design a fruit as suggested in the workbook.

Have a pleasant weekend.

Regards,

Lion Lim

Trumpet Tree in Singapore

http://www.nparks.gov.sg/cms/index.php?option=com_content&view=article&id=182&Itemid=161

The trumpet trees are commonly found in Singapore. The flowers are either pink or white. You can find a whole row of this tree along Yishun Ave 4 (along Safra Yishun Country Club).

I have attached a website that gives quite a detailed description of the tree.

Trumpet Tree (Tabebuia rosea)
Family: Bignoniaceae
The Trumpet Tree grows up to 18-25m tall, and has a large, broadly conical and shady crown. The tree’s name comes from its large trumpet-shaped flowers, which range in colour from pink to white.
The fruits are elongated pods, which split open to released winged seeds. This tree is known for its impressive flowering display, where the entire tree is spectacularly covered in blossoms. This takes place in April and August, usually after a dry spell.
When they flowers fall, they retain their colour for a couple of days, forming a beautiful carpet of flowers around the tree.

Flowers of the Trumpet Tree

Split fruit pod of the Trumpet Tree

Fruit pod of the Trumpet Tree

The fruit is elongated and it split open creating an explosive action. This creates a force that throws out the seeds. However, the seeds have wing-like structure that help them be disperse by wind after that.

Regards,
Mr Lim