In the Shanti Parva of the Mahabharatha, there is a very interesting and insightful conversation between the two great sages, Bhrigu and Bharadwaja. Bharadwaja seems to think that trees do not have life and expresses the same to Bhrigu. Bhrigu not only explains how plants have life but also brings out the role played by the elements in the functioning of the plant system and also elaborates on the various physiological processes including transpiration and photosynthesis, in just a few verses. He even attributes the sense of touch, sound and vision to plants. Let us see each statement of sage Bhrigu and also look at how they are in resonance with modern science.
While expounding about the nature of reality and the role of the Pancha Maha Bhutas, sage Bhrigu says that all mobile and immobile objects are made of the five elements and explains how the five senses of living creatures also partake of the five elements through various processes.
Bhradwaja upon hearing this, tries to apply this principle to the plants and trees gets a very relatable question. He asks that if all mobile and immobile objects are composed of these five elements, why was it that in all immobile objects those elements are not visible., especially in trees. He goes on to say, “The five elements are not noticeable in the trees. Trees do not appear to have any heat. They do not seem to have any motion. They are again made up of dense particles. Trees do not hear: they do not see; they are not capable of the perceptions of scent or taste. They have not also the perception of touch. How then can they be regarded as composed of the five (primaeval) elements?”
~ Trees have life. They are not inanimate.
~ Though dense, they have spaces within them (Akasha).
~ They constantly produce fruits and flowers. The drooping of their leaves, fruits, bark and flowers are a consequence of the property of heat they hold within them (Agni).
~ During lightning and thunder, through their sounds, the trees drop their fruits. Sound is perceived through the ears. Therefore, the trees have the ability to hear and perceive sound. (sound perception).
~ A creeper winds itself around a tree and goes around all its sides. A blind object, without vision, cannot find its way. Through this, it is also evident that trees have vision perception and can see. (sight perception)
~ Plants drink water through their roots (explained in detail, below). Thus, they have the perception of taste.
~ Plants are prone to sickness and drying up. They also grow back again when cut or chopped off. They not only have the perception of touch but are also very susceptible to pleasure and pain.
~ Trees have the inherent ability to recover. Trees are prone to different kinds of diseases and these diseases that the trees catch can be cured through different operations.
~ Trees produce many kinds of flowers with different kinds of odours — good and bad, of the sacred perfume of diverse kinds of dhupas. It is plain that trees produce scent.
In the following verse, Bhrigu explains the process of transpiration with a very easy to understand example:
vaktreṇotpala nālena yathordhvaṃ jalam ādadet
tathā pavanasaṃyuktaḥ pādaiḥ pibati pādapāḥ
As one sucks water upwards with help of lotus petiole, trees drink water through the roots with the help of air.
Here, using the example of a bent lotus-stalk, Bhrigu refers to the capillary action in plants which helps the plant suck up water through narrow spaces against the force of gravity. Xylem, the plant vascular tissue is made of millions of tiny cellulose tubes. Water molecules rise up through these tubes through the stem up to the leaves due to the forces of cohesion and adhesion. Transpiration of water through the leaves helps to pull more water from the roots. This process is called capillary action. Trees and plants cannot drink through their roots without capillary action.
The lotus stalk has visible holes and capillaries as can be seen from the cross-section view. Bhrigu using this example to illustrate capillary action, is again proof of their deep understanding of the microscopic world and microcosm.
In the Vrikshaayurveda by Parashara, the process of transpiration in plants is explained in more detail through the plant’s vascular circulatory systems. The nutritive sap that is held by the Earth is called Prithvi Rasa — the elementary fluid. This sap is absorbed by the plants through the roots. The root is called mula - that which helps fix the plant to the soil. Through it, the plant drinks the rasa from the earth. Syadani is the vascular circulatory system of the plant that helps the roots and performs the function of transporting the Rasa. Sira is the part of the plant’s circulatory system that helps circulate the absorbed rasa in both inward and outward directions.
The cohesion-tension theory explains how leaves pull water through the xylem. Water is absorbed at the roots by osmosis, and any dissolved mineral nutrients (rasa) travel with it through the xylem. Water molecules stick together, or exhibit cohesion. As a water molecule evaporates from the surface of the leaf, it pulls on the adjacent water molecule, creating a continuous flow of water through the plant.
Bharadvaja then asks Bhrigu what happens to the water after it is absorbed by the root and enters the plant. Bhrigu explains the process of Photosynthesis as follows:
tena taj jalam ādattaṃ jarayaty agnimārutau
āhāraparināmāc ca sneho vṛddhiś ca jāyate
Fire (from the sun and internal heat) and wind (caron dioxide) cause the water thus sucked up to be digested and aids in the production of food in the plant. According, again, to the quantity of the water taken up, the tree advances in growth and becomes humid.
The process of photosynthesis by which plants convert the sunlight and carbon dioxide into simple sugars and oxygen is thus referred to by sage Bhrigu.
This also, in alignment with modern transpiration theory establishes that the rate of transpiration is directly influenced by the temperature, sunlight and surrounding air. In actively growing plants, water is continuously evaporating from the surface of leaf cells exposed to air, causing a negative pressure (suction force) in the xylem that pulls water from the roots and soil.
Presenting the above points, sage Bhrigu establishes thus: “From these circumstances, I see that trees have life. They are not inanimate.”