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Cotton for breakfast

December 7, 2012

Two days ago we were visited by Dr Alvin Yoshinaga from Hawaii and his Thai (Esan) wife Khun Onanong Prommart, nicknamed Mot. Enthusiastically Mot showed me how you can eat the young fruits of cotton (Gossypium spp., Malvaceae).

Gossypium fruit.December6.2012.72

Cotton fruits are a bit sweet, quite tasteless, but I am always thrilled to learn about new edibles. I asked Kate (also from Esan) if she knew about this, and she said “Yes, of course”. This is another example where my Thai family carry interesting information they think is so basic it is not worth mentioning.

Cotton seed oil is another edible product from cotton, used for cooking. It makes sense, since the cotton industries worldwide must have a gigantic byproduct of seeds, and the oil is tasteless and therefore equivalent to canola oil.

Gossypium corolla, calyx, epicalyx.72Botanical literature often deter amateurs by using a technical language. This is one reason extensive botanical knowledge is mostly limited to a small group of academics. I believe that is dangerous, since we need many aware eyes to keep Earth’s flora alive. I shall do my best to pave the way for inviting amateurs to use the flora of China keys: What we normally call a flower, the coloured part to the right, is often referred to as ‘corolla’ in botanical literature. At the bottom of the corolla is a green cup-liked structure with black dots. This cup of sepals is called ‘calyx’. The large leaf with teeth to the left is of diagnostic importance, and is called ‘epicalyx lobe’. The epicalyx wraps the flowering bud and remains also in the fruit (a dry capsule) making it useful for identification.

According to Mabberley’s plant book there are 49 species of cotton, of which mainly four are used commercially for textile fiber. The many varieties within each species makes an identification sometimes difficult if the grower or vendor does not keep track of its origin. Internet is swamped with pictures with dubious identifications. To my experience, colours, plant size and leaf shapes vary so much they can not be used as reliable characters for identification. You can distinguish these four cotton species using my facilitated version of the Flora of China key (which contains inconsistencies too if you compare the species descriptions with the key characters):

1. The green leaves surrounding the fruit (epicalyx lobes, ‘bracts’) are fused (connate) at the base……………………………………………………………………………………………………………………….2.

1. Epicalyx lobes free at base…………………………………………………………………………………….3.

2. Epicalyx lobes longer than wide……………………………………………………………G. arboreum.

2. Epicalyx lobes wider than long……………………………………………………………G. herbaceum.

3. Three epicalyx lobes…………………………………………………………………………….G. hirsutum.

3. Five or more epicalyx lobes……………………………………………………………….G. barbadense.

Tree cotton (Gossypium arboreum), is native to west Asia and has been cultivated since 1800 BC.

Barbados cotton, Egyptian cotton (G. barbadense), is native to tropical America.

Levant cotton (G. herbaceum), was domesticated in East Africa.

Mexican cotton, Upland cotton (G. hirsutum), is native to Central America.

As can be seen from this overview, cotton is not native to neither China (the world’s largest producer) nor Thailand. The cotton genus and all four commercial species were described by the Swedish gentleman Linnaeus in the 18th century. He used Pliny the Elder’s name for cotton: ‘gossypion’, ultimately derived from Arabic ‘goz’. ‘Cotton’ is also of Arabic origin (kutn, qattan). The Sanskrit name for cotton is ‘karpasa’ which influenced Greek (karpasos) and Latin (carbasus), but ‘carbasus’ may refer to any fiber or fabric such as flax (Linum sp., Linaceae).

Gossypium staminal column.72This picture shows a sectioned cotton flower where I have removed the epicalyx. Inside the whorl of yellow petals is the ‘staminal column’, with the female stigma seen at the very top, and pollen-producing stamens along the column. The length of the filaments (the stalks holding the yellow anthers) are sometimes considered important for making an identification. I consider this species Gossypium herbaceum based on the facts the epicalyx lobes are fused, there are only three such lobes, the filaments are of equal length, the plant is short lived and the calyx is cup-shaped. According to Tem Smitinand’s ‘Thai Plant Names‘ the general Thai name for this species is ‘fai’.

Another obstacle for amateurs using for example Flora of China, is that the most conspicuous feature, the flower, is described as “yellow with a purple centre”, and with an impressive diameter (5-7 cm). In reality, red blotches are often absent in domesticated mallows and whether you study the flower at 9 a.m. or at noon will have a great impact on its shape (funnel or flattened). When the flower gets old, it develops pinkish colours.

Gossypium boll.72Young cotton plants are quite attractive when their fruits open and display the cotton fibers. The organic Dokmai Garden cotton is snow-white, so I do not understand the debate in my youth when the cotton industry argued they had to bleach cotton with chlorine. In a monsoon garden you should allow cotton to have dry and wet seasons, and although you should consider this old world cotton species short-lived, 1-2 years, the seeds are very easy to germinate.

Note the spots on the young cotton fruit, which are gossypol glands also present in the petals and the calyx. Their function is to deter hungry insects, like the glands in oranges. In the hibiscus/mallow family (Malvaceae), this is a unique feature of the cottons (tribe Gossypieae).

An amazing review on the pedigree (evolution) of the commercial cotton species was published by Wendel and Cronn (2003) Polyploidy and evolutionary history of cotton. Advances in Agronomy 78: 139-186. Molecular studies show that Old World cotton (an ancestor of African G. herbaceum) may have crossed with American cotton (an ancestor of G. raimondii) creating five new species including G. hirsutum. This species constitutes 90% of today’s industrial cotton. The question is, was this crossing recent and man-made (a few thousand years ago when the Asians colonized America) or did it even happen before South America broke up with Africa 60-100 million years ago?

The current hypothesis, based on molecular analyses and mutation clocks, is that the crossing happened in Central America 1-2 million years ago, before the dawn of modern humans. Based on the presence on close G. hirsutum relatives in Hawaii and the Galapagos islands, rather than in the Atlantic, it is further hypothesized that the African-American crossing was trans-Pacific via Asia. At the time, the ancestor might have been native to Asia, and its closest relative today is African G. herbaceum. Multiple molecular studies support the hypothesis that this crossing only happened once. This implies either the unlikely transfer of one cotton pollen grain across oceans to another cotton flower’s stigma, or the transfer of a seed by oceanic drift.

Text & Photo: Eric Danell

(Temperature report: we have had a number of clear nights and earlier this week we had the first temperatures below 20 °C this cool season. Previous night the low hit 16.6 °C. Afternoon temperatures peak around 30°C).

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