Ever wondered where the expression “a kernel of truth” comes from?
It is fascinating to me that “truth” is associated with plant kernels.
Why this association? Is “truth” hard? Or is “truth” hard to find?
Perhaps then, another question could be “What is a kernel”?
Colloquially, the term “kernel” is used to refer to any kind of hard seed, or even the husk of certain grains. In fruits such as plums and peaches, the hard “seed” is also known as the “stone”, an apt description that comes to mind when one bites to hard into a plum fruit. Yet, these terms kernel, husk and stone are not very precise botanically.
Plant scientists take terminology very seriously, and are pretty religious about the specific terms they use for fruits. After all, it has been said that “by their fruit shall ye know them”. Therefore, fruits that have a hard kernel inside are known as specifically as drupes, and these includes all the fruits known as “stone fruits” and also walnuts, pecans, mangoes, and even coconuts.
Many drupe type fruits have a fleshy nutrient rich pulp layer over the tough fibrous or woody kernel to attract animal dispersers. The so-called “stone” or kernel is not actually the seed, but an envelope or casing within the fruit that protects the seed.
Delving into how fruits and seeds develop are of scientific interest because understanding how fruits develop is important for farmers and agriculturists who cultivate commercial fruits.
Fruit development also has taxonomic importance, and can help taxonomists understand relationships between different plants. For example, understanding whether a character is derived (i.e. a character that the current organism possesses that the previous do not) can help to illuminate taxonomical relationships between species.
Enter the Elaeocarps
The genus Elaeocarpus is a large genus (c. 350 species) of predominantly tropical rainforest trees. The ethymology of the genus Elaeocarpus actually means to “Olive fruit”, which refers to the olive-like appearance of many species in the genus.
Despite the huge diversity within the genus, Elaeocarpus is probably not very well known outside of Asia. In Asia however, the genus plays a significant role in the maintenance of forest diversity and ecology. In tropical Australia for example, the nutrient-rich fruits of Elaeocarpus species are an important food source for a large number of rainforest bird and mammal species.
In some Asian countries, certain species of Elaeocarpus also play a significant role in religious practices, as the hard stones of these species are used to make rosaries. In some southeast Asian countries as Papua New Guinea and Australia for instance, various fruit stones of Elaeocarpus are used by indigenous people as spiritually-significant objects and also as jewelry. In India for instance, Hindus and Buddhists revere Rudraksha beads, which come from various species of Elaeocarpus (primarily E. sphaericus and E. angustifolius). Some Elaeocarpus beads with special shapes or features such more or less than 5 lines running down the side of the seed (5 lines is the normal condition) are especially revered and attributed special spiritual properties.
Elaeocarpus is an interesting genus to study because of its huge diversity (Read more about tropical Australian Elaeocarpus). Many Elaeocarpus species have a hard or semi-hard fruit layer called the inner mesocarp.
Some Elaeocarpus exhibit an interesting pattern in the seed, whereby the endosperm (i.e. the tissue in the seed that surrounds and feeds the developing embryo) has a convoluted ruminate pattern when seen in cross-section. This is not a common characteristic in seed plants, but has been documented for about 57 other botanical families of plants. Also, not all species within a plant family will exhibit ruminate endosperm, and among the 350 members of Elaeocarpus, only 28 species so far have been found to possess this condition.
Our recent work on fruit anatomy is led by Janet Gagul, a botanist from Papua New Guinea is about to complete her Ph.D thesis on the systematics (i.e. the study of plant classification) and developmental biology of Elaeocarpus from the Australia and Papua New Guinea. Janet is working with Professor Darren Crayn at the Australian Tropical Herbarium, who has published widely on the systematics and biogeography of Elaeocarpus.
Janet was interested to understand the hardening process of the mesocarp, and also the development of ruminations within the seed endosperm during the process of fruit development, and to understand whether this character is derived. And for her study, there was no better species to study than Elaeocarpus ruminatus itself, a species that was named on the basis of having the ruminate endosperm character. Janet collected fruits of the species every 2 weeks over a period of 6 months from the end of the flowering period to time fruits were mature. We then made anatomical sectioned of these fruits at these different stages of development to see how the seed develops.
Our observations have now been published in Australian Systematic Botany. Essentially what we found was that the hardening of the mesocarp is a process that takes place before and independently of the development of ruminations in the endosperm. And secondly, endosperm ruminations are a derived character within Elaeocarpus.
The time to ruminate
If the purpose of religion is to get closer to truth or divinity, it is fitting that the hard “stones” of Elaeocarpus should feature so prominently in religious or spiritual practices. Whether it is the need to contemplate on a hard “truth”, or to delve within to see the “truth”, every Rudraksha bead contemplated upon or counted hopefully brings us closer to understanding divinity.
And what of our foray into the anatomy of a “stone” fruit?
I think that anatomical exploration is a metaphor for the search for “truth”. On this journey, I have seen and am properly awed by the simple and sophisticated beauty of the different cells and tissue layers that make up the fruit of Elaeocarpus ruminatus. Perhaps “beauty is truth, and truth is beauty”, as John Keats famously said. In hindsight, I’d offer yet another philosophical metaphor, specifically for what Elaeocarpus ruminatus may teach – DEVELOP A FIRM INNER STRUCTURE, AND THEN RUMINATE!
Corner EJH (1976) ‘The Seeds of Dicotyledons.’ (Cambridge University
Press: Cambridge, UK)
Gagul JN., Tng DYP, Crayn DM (2018) Fruit developmental biology and endosperm rumination in Elaeocarpus ruminatus (Elaeocarpaceae), and its taxonomic significance.” Australian Systematic Botany 31, 409-419.
Phoon SN (2012) Rudraksha: the bead tree of India and related species. Gardenwise 38, 22–25.