Pineapple

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Pineapple
Scientific Classification
Kingdom: Plantae Subkingdom: Tracheobionta Superdivision: Spermatophyta Division: Magnoliophyta Class: Liliopsida Subclass: Zingiberidae Order: Bromeliales Family: Bromeliaceae Genus: Ananas Species: A. comosus
Binomial Name
Ananas comosus
Image Description

Introduction

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Obtain your taxonomy information from the U.S. Department of Agriculture.

Anatomy

This flowering pineapple has violet petals. Each flower develops into a fruit that becomes part of the fused syncarp.

Pineapples are herbaceous, terrestrial members of the Bromeliad family [1]. The plant is typically two to five feet high with a short stem [2]. The leaves are large, at one to three feet in length, and grow from the soil at the base of the stem [3]. The leaves have a waxy coating and have needles or spines on the tips [4]. These leaves grow in a circular pattern called a rosette, and they may be green in color or have red, yellow, or white stripes [5]. Pineapples have simple leaves with spiny margins and parallel leaf venation [6]. Pineapple leaves are adapted to allow pineapples to survive periods of drought better than other tropical plants. The leaves form around the stem in an overlapping spiral, and water collects in the "bowl" formed by the overlapping leaves [7]. In addition, the thick cuticle prevents water loss, as does the use of the CAM pathway to fix carbon dioxide for photosynthesis, which only requires that the stomata of the leaves be open at night, rather than during the day as well [8].

Pineapples have roots underground, as well as some aerial roots. Roots in the soil may grow up to 2 meters long and 85 cm deep, but their growth may be restricted if the pineapple is not cultivated in proper soil [9]. Aerial roots grow between leaves on the stem and wrap around the stem, allowing additional moisture to be absorbed [10].

In summer, when the plant is ready to bloom, the stem grows longer and the tip enlarges [11]. Flowers with red or purple petals grow from the stem's apex, accompanied by yellow, red, or green bracts (scale-like modified leaves) [12]. A cluster of smaller leaves also develops atop the flower cluster [13]. If the flowers are to produce seeds, they must be fertilized by a pollinator (usually hummingbirds), because pineapples are incapable of self-fertilization [14]. Most pineapples grown commercially have undeveloped seeds or lack them altogether [15]. Pineapple growers do not grow their crops from seeds and take measures to discourage pollination as it is not necessary for the fruit to develop. Flowers remain on the plant for about two weeks, with the flowers nearest the base being the first to open [16].

After flowering, it takes an additional six months for the fruit to fully develop, and only one fruit is produced per year [17]. The pineapple fruit, called a syncarp, is actually over 100 developed ovaries fused together, each one from a separate flower [18]. The oval-shaped fruit may grow to a foot in length and weighs ten pounds or more at maturity [19]. The sweet, juicy interior of the fruit is edible and ranges in color from white to yellow [20]. The stem of the plant forms the core of the fruit and is much tougher and more fibrous than the rest of the fruit [21]. The syncarp also has a thick, waxy rind made up of hexagon-shaped eyes that turns dark green, yellow, yellow-orange, or red when the fruit ripens [22]. Each eye is located on a separate ovary in the fused compound fruit [23].

The pineapple puts forth shoots from the base of the fruit, leaves, or stem. Shoots from the base of the fruit are called slips, those growing from the axils (base of the leaves) are suckers, and the underground shoots from the stem base are ratoons [24]. These shoots are all capable of growing into new plants.

Reproduction

Pineapples reproduce asexually through four different methods: slips, suckers, crowns, and ratoons. Slips are shoots that grow from the stem at the base of the fruit. Suckers grow from the leaf axils (bases). Crowns come from the top of the fruit, and ratoons are root-like shoots that grow from the stem beneath the soil. All of these forms of vegetative growth, called propagules, may be removed from the parent plant and used to propagate new pineapple plants. This is the primary method of propagation used by commercial pineapple growers [25]. Slips and suckers are used more often for commercial growing, but the crown of a store bought pineapple can be used to grow a pineapple plant at home [26].

After removing the propagule from the parent plant, the propagule should be allowed to dry and cure for one to two weeks to allow roots to develop before planting, and it should be kept warm while it is being cured [27]. The crown can be placed in water to cause the roots to develop [28]. After this, the young plants can be placed in the ground or cultivated in a pot. Pineapples prefer soil that is slightly acidic (pH of 4.5 to 6.5), sandy, and has good drainage [29]. They should be grown in full sun for the best fruit, and proper amounts of nitrogen are necessary, which can be supplied through a fertilizer [30]. Potassium is also important, and the addition of magnesium has been shown to increase size and weight of the fruit [31]. A pineapple grown from a propagule will produce its first fruit 12 to 22 months (about 1 to 2 years) after planting [32]. The length of time required for a fruit to develop depends on a number of factors including temperature and the size and type of propagule used. A larger propagule will generally bear larger fruits in less time [33]. Only one fruit is produced per year, and the best fruit is obtained in the first 3 to 5 years of fruiting, after which a new plant should be grown [34].

Pineapples may also be produced sexually from seeds, although this method is often less successful than growing them from propagules and is not possible with store bought pineapples because commercial growers breed pineapples without seeds. Seeds may be allowed to germinate naturally or chemically treated with sulfuric acid to bring about quicker germination [35]. Since pineapples are self-incompatible (unable to self-fertilize), they will only develop seeds if they are cross-pollinated with another plant [36]. Their primary pollinators are hummingbirds, which have been banned in Hawaii, one of the chief pineapple growing areas [37]. In addition, pineapple fields often contain row after row of identical plants grown from propagules that cannot cross pollinate because they are genetically the same [38]. If a pineapple were to be cross-pollinated and develop seeds, there would be hundreds of tiny brown seeds in a single syncarp, with one seed for each individual fruit in the fused pineapple [39].

A unique feature of pineapples is that the fruit does not continue to ripen after it has been picked. This is because the fruit does not have a starch reserve that would allow the fruit to ripen any further [40]. However, if any yellow-orange is showing at the bottom of the pineapple, it means that sugar has begun to develop and the pineapple will taste sweet [41]. Due to quick methods of shipping now available, such as air shipping, pineapples can reach their destinations as soon as three days after being picked, allowing them to be harvested ripe without spoiling in transport [42]. A pineapple may be ripe even if it is still mostly green as long as the bottom has begun to change color.

Flowering can be forced to obtain fruit sooner than it would naturally develop [43]. This is useful to pineapple growers as pineapples do not always flower regularly, especially in unfavorable conditions [44]. Treatments containing ethylene, acetylene, or calcium carbide solution sprayed on the plant will cause flowering, and fruit can be harvested about six months after forcing [45] [46]. Placing pieces of apple in with the plant can also force flowering because apples give off ethylene gas [47]. Hormone and chemical sprays can also be used to achieve uniform fruiting in a large field so all of the crop can be harvested at the same time [48]. Forcing may result in inferior fruit on weaker plants, but the plants can be treated to produce larger, heavier fruits using hormone treatments [49] [50]. Typically, hormone and chemical treatments are sprayed on the leaves to collect in the tight spiral "bowl" along with water and be absorbed by the plant.

Ecology

Description

Pineapples are tropical plants that can grow in most warm climates with temperatures of 65 to 95 degrees Fahrenheit [51]. Pineapples are easily harmed by frost. Temperatures should not fall below 60 degrees for very long, and temperatures of around 28 degrees cause serious damage to the leaves as well as a more acidic fruit if the plant survives [52]. Pineapples should be grown in full sun for the best fruit, or in partial sun for ornamental purposes [53].

Soil should be sandy and loamy with good drainage as pineapple roots cannot grow well in hard soil [54]. The soil needs to be mildly acidic, with a pH of 4.5 to 6.5 [55]. They should be watered regularly to ensure quality fruit production, but they can be harmed if too much water accumulates in the soil due to poor drainage [56]. Due to their stomata and use of the CAM pathway for photosynthesis, pineapples withstand droughts very well for a tropical plant.

Pineapples are native to South America, but have since been introduced in warm climates all over the world because of their sweet, desirable fruit. They are believed to have been grown first by the Guarani Indians in Brazil and Paraguay [57]. The Guarani Indians took pineapples on their sea voyages to places such as the Caribbean Islands, where Christopher Columbus encountered them in 1493 [58]. Columbus introduced the pineapple to Europe, where it was grown in greenhouses. It became a favorite fruit of kings and the wealthy, but as it was cultivated in more tropical areas around the world, it became increasingly available [59]. Today, pineapple is grown in Hawaii, Puerto Rico, Malaysia, and Brazil, as well as China, Florida, Thailand, the Philippines, India, Nigeria, Costa Rica, Mexico, and most other tropical countries [60] [61] [62]. Hawaii is currently the largest producer of commercially grown pineapples [63]. Most pineapples grown are canned, but they are also sold fresh or as juice, and the fibers of the leaves are used in many countries as well [64].

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References

• PLANTS profile for Ananus comosus (pineapple) Natural Resources Conservation Service. Unites States Department of Agriculture (USDA). 4/9/09. accessed 4/9/09.
• link title Author. Publisher. Date
• link title Author. Publisher. Date

See Also

• Botany

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