How do plants drink? An insight into the water supply

They look like little drops – apple seeds. Have you ever wondered how these tiny seeds turn into magnificent apple trees? What do they need to germinate and grow? Whether it’s an apple tree, a raspberry bush, a sagebrush or a radish, they all actually want the same thing: sun that provides light and warmth, nutrients and minerals in the soil, and plenty of fresh air. And of course water!

Roots: a question of type

In order to absorb water from the soil, plants need roots. Each has its own unique tricks. So-called deep-rooted plants such as citrus trees or vegetables such as beet or tomatoes develop long roots that penetrate into deep soil layers in order to tap into the water reserves there. Shallow-rooted plants such as berry bushes, apple or plum trees, on the other hand, spread their roots like a net just below the surface of the soil. Their secret weapon: intercepting water that trickles down over as wide an area as possible before it seeps away. Then there are plants that combine the best of both abilities, the so-called heart-rooters like many vegetables, e.g. kohlrabi, broccoli or peas.

Combining different types of roots in the vegetable patch is definitely a super thing to do, as this way they don’t have to compete for water. We will go into more detail about this principle of mixed culture in another article.

Here’s a little overview of the root systems of some of our Bloomify plants:

shallow rooter	Deep-root	Heart Root
Apple, peach, apricot, nectarine olive, zucchini all berry bushes kiwi, mini kiwi oregano, thyme, marjoram, lemon balm, mint	Plum and plum (but also form shallow root runners), pear all our citrus trees vine tomato, chili, bell pepper, pumpkin, carrots, beet rosemary, sage, lavender, parsley, coriander, tarragon.	Cherry Fig Eggplant, Cucumber Basil

The way of water

But how does the water actually get into the roots and from there into the leaves? The root cells are able to absorb the water because the water concentration in them is lower than in the soil, and the water in the soil therefore flows into the cells to compensate for this difference. This process of equalization is called osmosis. The walls of the roots are built in such a way that the water can only pass through in one direction, so it cannot flow back. This flow creates the so-called root pressure. However, it alone would not be sufficient for the long distance that the water has to travel in the plant. There is also transpiration suction, which occurs when water evaporates through the leaves. Evaporation causes water molecules to leave the plant and a negative pressure is created, which causes new molecules to “move in”, they are virtually sucked in. Water molecules also have the practical property that they attract each other and thus move each other upwards as a kind of chain. This mutual attraction is called cohesion. In this process, the molecules rise upward in the stem, stalk or trunk of the plant in a “tube,” similar to a straw. There are also forces between the water molecules and the wall of this tube, which additionally support the molecules on their way up. This process is called adhesion. Cohesion and adhesion in interaction are in turn called the capillary effect.

So amazing processes take place inside plants that remain hidden from our eyes. We usually only see that wilted leaves slowly straighten up again after a watering after some time – but it is super interesting what is happening inside the plant during this time.

Water as a nutrient cab and photosynthesis helper

Now the question arises as to why the plant actually goes to such lengths to transport water from the soil all the way to the top of the leaves. One reason is nutrient uptake. Minerals in the soil are usually present in a form dissolved in water and are therefore absorbed together with the water molecules. The other reason is probably familiar to you from biology class: photosynthesis. With the help of this process, a plant can produce the energy-rich substances it needs to grow and thrive.

Photosynthesis takes place in the leaves and is set in motion by light. The leaves contain chlorophyll, which can absorb light. So the plant uses the energy from sunlight to in turn produce energy that it can metabolize. Pretty impressive, right?

But light alone is only the beginning, the igniting spark, so to speak. In various process steps, oxygen (O2) and the energy-rich glucose (grape sugar) are produced from carbon dioxide, i.e. CO2, which the plant takes up from the air via its leaves, and from the water (H2O) that has arrived in the leaves via the roots. Humans and animals need oxygen to breathe, but it is actually just a “waste product” of the plants that is released back into the surrounding air through the leaves. The plant is only interested in the sweet glucose.

The entire process of photosynthesis is more complicated than we’re making it out to be here, but a quick summary still gives a good overview of what else exciting happens to the water you give your plant when you water it.