Carambola, Jaboticaba, Banana Mangosteen & Kiwi

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Economic Plant Photographs #7

Carambola, Cucumber Tree, Jaboticaba,
Banana, Mangosteen and Kiwi

Oxalis Family (Oxalidaceae): Carambola

The carambola or "star fruit" (Averrhoa carambola), an elongate, angular fruit composed of 5 carpels with a star-shaped cross section. The tartness is due to calcium oxalate crystals in the flesh which dissolve in the saliva forming oxalic acid. This interesting tropical fruit comes from a pinnately-leaved tree native to Malaysia. The curious 5-angled fruit is usually cooked with sugar. It is also used in salads, as a garnish, and in preserves and chutneys. This species is especially interesting because it belongs to the oxalis family (Oxalidaceae). In fact, the shape of the fruit resembles a giant version of our common southern California weed Oxalis corniculata.

The carambola tree (Averrhoa carambola), with cauliflorous flowers and "star fruits" that arise from the main trunk. The curious fruit of this Malaysian tree is used like the following species called the cucumber tree (A. bilimbi).

Oxalis Family (Oxalidaceae): Cucumber Tree

The cucumber tree (Averrhoa bilimbi), a relative of the carambola with cauliflorous flowers and fruits that arise from the main trunk. The curious fruit of this Malayan tree is used like the carambola.

Myrtle Family (Myrtaceae): Jaboticaba

Jaboticaba (Myrciaria cauliflora), an interesting cauliflorous member of the myrtle family (Myrtaceae) native to southern Brazil. The globose, grapelike fruits develop directly from the trunk and branches. At maturity the sweet berrylike fruits become dark purple, with a flavor somewhat intermediate between a grape and a plum. They are eaten fresh, and used for desserts, sauces, preserves and wine.

Go To Article About Cauliflorous Plants

Banana Family (Musaceae): Banana

A banana plant in full bloom. The elongate, pendant, bisexual flower stalk has purple bracts at the end resembling a large bud. Just above the purple bracts are clusters of old, stamen-bearing male flowers. Farther up on the stalk are clusters of immature bananas that developed from clusters of ovary-bearing female flowers.

A banana plant in full bloom. The elongate, pendant, bisexual flower stalk has purple bracts at the end resembling a large bud. Some of the basal purple bracts have fallen away exposing clusters of female flowers. Farther up on the stalk (farther from the apex) are clusters of immature bananas that developed from clusters of ovary-bearing female flowers.

Close-up view of fleshy, berrylike (baccate) banana fruits. The small black dots inside are the remnants of aborted ovules that did not mature into seeds. Since this fruit develops on a sterile plant without fertilization it is termed parthenocarpic.

The cultivated banana is often listed in botanical references as Musa x paradisiaca (Musaceae), although it is actually a complex hybrid derived from two diploid Asian species, M. acuminata and M. balbisiana. Common cultivated bananas are usually triploid (3n) with three sets of chromosomes. [Note: The word "set" is defined here as one haploid set of chromosomes.] If A represents one set of chromosomes from diploid M. acuminata (AA) and B represents one set of chromosomes from diploid M. balbisiana (BB), then hybrid bananas have three sets of chromosomes represented by AAB, ABB or another 3-letter (triploid) combination of A's and B's. Like seedless watermelons and red grapes, bananas are sterile and do not produce mature seeds. [Sometimes you can find aborted ovules inside the fruit that appear like tiny black dots.] Bananas are sterile and seedless because they are odd polyploids in which one set of chromosomes (A or B) has no homologous set to pair up with during synapsis of meiosis. Therefore meiosis does not proceed normally, and viable gametes (sex cells) are not produced. Since banana fruits (technically berrylike ripened ovaries) develop without fertilization they are termed parthenocarpic. Without viable seeds, banana plants must be propagated vegetatively (asexually) by planting corms, pieces of corms or sucker sprouts.

See The Genetics Of Parthenocarpic Bananas
See Hybrid Parthenocarpic (Seedless) Bananas
The Genetics Of Triploid Seedless Watermelons

The genes of sterile transgenic crops, such as bananas, are not as likely to escape into the environment through seeds or pollen. Because edible bananas do not produce seeds, new groves are planted from cuttings of existing stock; however, this asexual propagation also spreads diseases and pests, such as the black sigatoka fungus, nematodes and weevils. Modern tissue culture methods will allow existing strains to be reared in a disease-free environment resulting in clean planting stock. Genes from other banana strains can also be inserted into existing stock to produce disease resistant, transgenic strains.

The banana plant is actually a giant herb that produces a large, pendant (drooping) flower stalk (inflorescence) bearing male and female flowers. Stamen-bearing male flowers are produced in clusters at the end of the stalk, just above the large, purple bracts that appear like a giant bud. Ovary-bearing female flowers are produced in clusters farther up the flower stalk and give rise to clusters of banana fruits. Bananas include many cultivated varieties (cultivars), including the fleshy, nutritious bananas that are peeled and eaten raw, and firm plantains that are fried and roasted like delicious sweet potatoes.

Garcinia Family (Guttiferae): Mangosteen

The mangosteen is often called the "queen of tropical fruits" because it is considered by some people to be one of the most delicious fruits on earth. It comes from Garcinia mangostana, a small tree in the garcinia family (Guttiferae) native to tropical Malaysia. Some botanists refer to this family as the Clusiaceae. Like many other trees and shrubs in this family, such as Clusia rosea and the mammee apple, the leaves are evergreen and leathery. The mangosteen fruit is technically a berry with a tough, leathery rind enclosing a white, fleshy mesocarp. After peeling, the mesocarp divides into juicy seed-bearing sections. The number of sections corresponds to the number of lobes at the apex of the rind. Each section contains a seed surrounded by a white, fleshy layer (aril). Mangosteen seeds typically contain nucellar embryos which develop apomictically from nucellar tissue surrounding the embryo sac. Since nucellar embryos are chromosomally identical to the sporophyte parent, the seeds of mangosteen are used to propagate clones of this delicious fruit tree.

Read About Apomixis & Agamospermy

There are several other species of Garcinia with edible fruits. A yellow gum resin obtained from incisions in the bark of several Asian species (including G. morella and G. hanburyi) is the source of the artist's yellow dye called gamboge. It was the traditional yellow dye used for the silk robes of Buddhist monks and the prime ingredient of certain yellow paints and inks. The raw resin turns brilliant yellow when powdered and gives a deep yellow emulsion when mixed with water.

The left photo shows a developing mangosteen fruit (Garcinia mangostana) just after flowering. The mangosteen is a small tree in the garcinia family (Guttiferae) native to tropical Malaysia. The inner mesocarp of a ripe fruit divides into juicy seed-bearing sections. The center and right photos show the fruits of a related species of Garcinia (G. dulcis). The brown seeds are covered with a fleshy layer (aril). The unripe fruits of G. dulcis have been used as a source of gamboge dye.

Actinidia Family (Actinidiaceae): Kiwi or Chinese Gooseberry

Kiwi or Chinese Gooseberry (Actinidia chinensis), a large vine native to China with fleshy, egg-sized (chicken egg), brownish fruit covered with soft hairs. A member of the actinidia family (Actinidiaceae), it is also listed in some references as A. deliciosa. The berrylike fruit has a delicious, sweet and slightly tart flavor that is somewhat intermediate between banana, melon and strawberry.

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