GO! GO! GO! H2O... Climb up the tree. 🌊 🍀

One of the daily chores assigned to me by wife is 'watering the plants'. Quite fond of plants, I have happily taken up the task and do it religiously, every morning. My mom too has a penchant for gardening. We even had a 'kitchen garden' at our home in Agra, boasting of vegetables such as Cauliflower, Spinach, Radish, Beans, Tomato. I along with my younger brothers, Kushagra & Mayank, were given the onus of watering our organically produced veggies & at times, scare away the monkeys from destroying or rather savouring our prized cultivation. Prized it was, as to every guest who came to our house, it was sort of mandatory to showcase them our vegetable garden. The green chutni made from home grown coriander really had a distinct flavour and aroma, much to our delight and guests envy 😋. Good old days. I'm getting nostalgic!

Cutting back to the present day, on a pleasant and cool morning in Bangalore, I was watering the two beans climbers, which are close to 9 feet tall, but then a thought struck me. How does the water from the pot reaches up? I was taken back to one Biology class lecture, educating us on Capillary action. And it resolved my query. It really is an important scientific process, that holds answers to many of our trivial day-to-day applications. One such naturally occurring phenomenon is observed in plants. 

How does water moves from the roots up to the leaves?

The above question is really not an easy one. How does water moves upward, against the laws of gravity, to quench the thirst of leaves? Words like Capillary action, Xylem, Osmosis etc. might have come to your mind or must have rung a bell now, after reading them, further reminiscing you about your school days Biology class. Let me complete the picture by providing a  view of the process.

What is Transpiration?

Transpiration is an important process that provides impetus to the Capillary action. It is the evaporation of water from the plant surface via small openings called 'Stomata' present in leaves. Transpiration holds multi fold importance to plants, like: 

a) Providing water(from roots) & carbon dioxide(from outside environment) for photosynthesis

b) Movement of minerals to the leaves

c) Cooling effect

But how does water rise against gravity to reach the leaves?

Water molecules first enters the root from the soil through root hairs. The concentration of water molecules is less in the roots as compared to in the soil, which results in water moving from soil into the roots; a process called Osmosis. The water then moves upwards from root to xylem, which acts like a conduit or a tube that facilitates water molecules to move up. The upward movement is a result of two different reasons: Adhesion & Cohesion. Adhesion refers to the attraction of water molecules to the xylem vessels, while Cohesion is the mutual attraction between the water molecules (hydrogen bond).

What is Capillary action in plants?

Adhesion and Cohesion together forms the Capillary action, which results in the upward movement of water. Capillary action typically occurs when the Adhesion force becomes greater than the Cohesive force, thereby resulting in water molecules travelling towards the vessel. Since, Cohesion force is also into play, it brings along further water molecules, creating an upward flow of water. Water as evaporates from the leaves(Transpiration), creates pressure, thereby drawing more molecules upwards. This makes the water molecules being 'pulled up' to the leaves from the roots via the xylem vessels. Hence, a natural anti-gravity phenomenon is triggered.

Source: Lumen Learning

Capillary action is the reason of you drawing in your favourite juice using a straw, fountain pen drawing in ink, earthern lamp getting lit up. As with our previous blog on water, this article too ends with an experiment for you. What to do if you don't have a Red coloured flower to give to your 'friend'? See the video below and get the flower of desired colour. Witness the power of "Capillary Action". 

Nerd Notes:

1) While Xylem carries water up to the leaves, Phloem carries sugar from leaves down to the stem and roots

2) Plants also have a unique way to sustain harsh times, like camels have humps to withstand the dry climate. Stomata can narrow down the opening, if they need to preserve water, yet open enough to allow carbon dioxide in for photosynthesis. 

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Thanks for reading.
Prakhar