The Life of Plants

Come autumn, the maples turn into a chaos of colors. It is a visual treat for us but for the plant, it is a moment hanging between death and new life. All leaves are normally green because they have chlorophyll which helps photosynthesis. As a leaf ages, the production of chlorophyll is reduced and there is no more sufficient chlorophyll present to cover up the other pigments with other colors, for example, carotin, xanthophyll and so on.[i] So the green fades and yellow, red or brown takes over. It is also hypothesized the changing of color by autumn leaves also amounts to an adaptive strategy- the bright colors of leaves in autumn could be a warning signal to the parasitic insects that become active in autumn and that the change of color would confuse and fear them off from attacking the tree.[ii] There is also some profit for harmless insects in this. They can lay eggs on these trees without the threat posed by other parasitic insects who eat their eggs.[iii] How we humans also rely so much on our attire and make up to gain new friends and also to keep away undesired attention!

[i] Wyman, D. (1986), Wyman’s Gardening Encyclopedia, New York: Simon and Schuster, p.98.

[ii] Archetti, M. (2000), The origin of autumn colours by coevolution, Journal of Theoretical Biology, 205, pp.625-630.

[iii] Archetti, M. (2000), The origin of autumn colours by coevolution, Journal of Theoretical Biology, 205, pp.625-630.

Plants have bigger leaves to capture maximum sunlight for photosynthesis and so such plants are the ones that grow under the shade of a canopy of other trees. There are also disadvantages to having big surface area for a leaf as there will be more evaporation. However, these plants usually growing in the lower strata of a forest, there won’t be much direct sunlight falling on them. Hence the evaporation will be less. These plants will also usually have greater water availability as they live inside ecosystems with water abundance. Eg:- banana, yam, colocasia. Plants with smaller leaves are usually the ones that grow in water deficient ecologies. The reduced leaf size helps minimize evaporation. Eg:- neem, gooseberry, tamarind. The smaller leaves are also found to have longer major veins running through them for water flow, as compared to bigger leaves.[i] This helps them cope water scarcity by providing alternative water pathways to go around the bubble blockages that tend to form in the veins during dry spells.[ii] There is an economy of living that is in action here.

[i] Wolpert, (July 5, 2011), Being small has its advantages, if you are a leaf, UCLA Newsroom, Retrieved from http://newsroom.ucla.edu/releases/being-small-has-its-advantages-209430

[ii] Wolpert, (July 5, 2011), Being small has its advantages, if you are a leaf, UCLA Newsroom, Retrieved from http://newsroom.ucla.edu/releases/being-small-has-its-advantages-209430

Modern plant science says, yes. When being eaten by animals and insects, certain trees and plants can not only secrete toxic substances to ward them off but also the scent of these substances give a warning to nearby trees thereby prompting them also to secrete the same toxins.[i] Also when attacked by leaf eating insects, some trees summon up the predators of those very same insects by secreting certain pheromones, which are predator-specific and insect-specific.[ii] This fact keeps one wondering whether plants can see what the other plant is doing, or if they can smell these secreted toxins or whether they can speak and hear a language of their own passed on through the atmosphere. The fact is, the tree roots communicate with each other through the fungi network attached to all of them, by way of their root network, and this network is phenomenal.[iii] It spans across an entire continent if not the entire globe.[iv] This network is what scientists call, the wood wide web.[v] Trees share nutrients too through the wood wide web. Another experiment proved in an area where there are many willow trees, if caterpillars devour some trees, the infestation does not further spread around them.[vi] This is because of the neighbouring trees being warned somehow by the infested trees and as a result they producing some toxins in their leaves that ward off the caterpillars.[vii]

[i] Wohlleben, P. (2016), The Hidden Life of Trees: What They Feel, How They Communicate- Discoveries from a Secret World, London: Penguin UK.

[ii] Wohlleben, P. (2016), The Hidden Life of Trees: What They Feel, How They Communicate- Discoveries from a Secret World, London: Penguin UK.

[iii] Wohlleben, P. (2016), The Hidden Life of Trees: What They Feel, How They Communicate- Discoveries from a Secret World, London: Penguin UK.

[iv] Wohlleben, P. (2016), The Hidden Life of Trees: What They Feel, How They Communicate- Discoveries from a Secret World, London: Penguin UK.

[v] Wohlleben, P. (2016), The Hidden Life of Trees: What They Feel, How They Communicate- Discoveries from a Secret World, London: Penguin UK.

[vi] As cited in Chamovitz, D. (2012), What a plant knows, London: Oneworld Publications.

[vii] As cited in Chamovitz, D. (2012), What a plant knows, London: Oneworld Publications.

Most of the plants can adapt to different climates, geographies and ecosystems. It is a proven fact now that individual species of plants are gradually migrating north to overcome the situations created by climate change.[i] It is a slow exodus. The result will be that the biodiversity of the southern hemisphere of the planet will shrink whereas that of northern hemisphere will increase. The geopolitical consequences of such a change will be beyond today’s understanding and imagination. In Udagamandal, which is a lovely hill station in south India, one can see an array of exotic trees, brought in almost a century back by the British colony government, still thriving along the winding roads and pathways as well as in the natural shola forests. The environmentalists of this place have remained worried about the invasion of these exotic tree species into the shola forest ecosystem.

[i] Maschinski, J. and Haskins, K.E., (2012), Plant reintroduction in a changing climate: Promises and perils, Washington D.C.: Island Press. P.230.

It is the negative circumstances that prompt a plant to flower immaturely. For example, when there is water scarcity and a resulting threat of wilting, a sapling will flower in a last-ditch effort to sustain its line of heritage, to reproduce and protect the species survival. Actually, it is rather a drastic act of species continuation. If the drought persists, the plant will die but mostly after leaving behind a few seeds that can grow into new plants. All the energy and resources of the plant at this time will be redirected to the flower setting, fruit setting and ripening of the fruit. Modern agriculture makes use of this tendency to get maximum flowering from a crop. Just a few days before the flower setting, farmers stop irrigation and then the plants would flower like they are never going to flower again in their entire life! After the completion of flowering, irrigation is re-started. The result the farmer gets is maximum flower setting and maximum yield. Think about this- how strong nature’s urge is to protect each and every plant species even if it is at the imperilment of a few individuals within the species.

Climbing plants can sense the nearby tree or prop and grow towards that direction. If we change the position of the prop, the plant will also change its course. This is an observable fact and happens in a few hours’ time. How does the plant know the prop has changed position? Do they see, smell, or listen to their surroundings? What exactly is happening in as simple an act of a plant as moving towards the supportive prop? An experiment by Charles Darwin and his son Francis proved that the light sensitive cells of a seedling are located at the tip of its shoot.[i] So we can say, the eyes of the plants are on the tip of the shoots. As far as the purpose of the eye is to detect light, this is true. However, the plant has no central nervous system that can process this information and make a mental picture of the light as we do. Instead the ‘eye’ of the plant detects light and sends a signal to the plant parts that need to bend towards the light.

Plants can also detect smell. Dr.Consuelo De Moraes, an entomologist, conducted an experiment in which she showed the parasitic dodder plant, which gets itself attached to another plant like tomato and steals its nutrients from its stem, is led by the smell of the host plant.[ii] The scientist could even trick the dodder to get attached to sticks smeared with tomato smell.[iii]

It is clear there are many ways of seeing and smelling than the way we humans do it. Plants are not exempted from these sensory experiences as we would have believed once.

[i] As cited in Chamovitz, D. (2012), What a plant knows, London: Oneworld Publications.

[ii] As cited in Chamovitz, D. (2012), What a plant knows, London: Oneworld Publications.

[iii] As cited in Chamovitz, D. (2012), What a plant knows, London: Oneworld Publications.