I find if I want to figure out how something works it is important to know everything. I’m not very good at accepting things at face value if it means I’m not quite clear on how it works. Except possibly the remote control on the TV. That is way beyond me and I freely admit to asking the kids to switch it from X-box mode to my favourite TV channel so I can watch gardening shows (when they are on, they can be a bit few and far between on our screens – and also when we had a house… oh the good old days! But we’ll get a new one soon enough). When it is something I’m deeply passionate about, like the garden, then settling for a casual answer just isn’t enough. I need to know how and why, so I can be a better gardener with my new, vast quantity of sandy soil.
Sometimes this takes us to easy places, like the straight forward plant biology, but it can take us to the scary world of chemistry. Chemistry was never my strong point – it is like maths in disguise. But I need to push past school days trauma and dig about for the answer to “how does this absorb thing actually work?”
Deep breath…. Here we go…
Last time we discovered the intrepid root hair cells that get out amongst the soil, risking their fragile lives to hunt and gather the moisture and nutrients the plant needs. But it is all very well to say they absorb or gather, The thing is, they don’t ‘go about’. They are fixed, anchored – rooted to the spot. So they have their outreach as far as their root hairs will go. Generally they aren’t seeking anything out. They are more like the filter feeders of the ocean, like mussels and oysters, glued in position and hoping what they need comes by. They don’t go cracking open soil particles looking for what they need. And remembering the root hairs are microscopic single cells that take on the nutrients, then you need to consider the nutrients need to be really tiny, much smaller than the handfuls of fertiliser, compost, manure or other things you scatter about the soil between the growing season to enrich the soil. Things need to happen to that to make it accessible, but we’ll talk about how it goes from chunky to tiny another time. What we need to know now is about the tiny nutrients and how they get into the plant.
Technically nutrients are broken down into atoms and molecules. So going back to school chemistry – if you remember the periodic table – a colourful chart where most things have a short ID of who they are like C for carbon and N for Nitrogen, but others are just odd to confuse bewildered students like Au for Gold (what’s that all about? – it isn’t like G isn’t available or Go for that matter) and K for Potassium. Well this is a big list of all the chemicals in the world (which are atoms, and are the smallest form of chemical, from what I understand) that go together like Lego to make up everything in the world. It doesn’t matter if it is organic or not – everything in the world can be broken down to a collection of these individual things.
The atoms are joined with others in amazing combinations to become things. They are joined together with electric bonds. If you go back to the periodic table, each thing has a number which tells you how many …
Oh my goodness we have to go deeper – each atom has a nucleus, which is the main bit of it and in it are protons which are positive and neutrons which are neutral and then it has electrons, which are negative, around it – kind of like the planets around the sun. Now depending on how many of each the atom has ultimately determines if it is a negative atom or a positive one. Which determines who it can hangout with to become a molecule. (still sort of like the Lego block – still made of something but that ‘something’ (the plastic) if you broke that down it isn’t Lego anymore, but also looking at the Lego block – does it have two bumps or six?)
Did I mention I don’t like chemistry? – well I hope I’m not losing you as I’m in danger of losing myself here. But this is important because these atoms join together – electrically with their electron glue. I could go deeper into this but it is complicated. But essentially it is like a jigsaw – some fit together and some don’t. Plants need ones that are water soluble so they can easily join the flow of water through the plant via the xylem. If you think about it – the two hydrogens and the oxygen in water are like three kids dancing in a circle and then others come in and join them and the song changes, but there are some kids they don’t want to play with. But also there is a limit to how big the circle can be so even some of the ‘right’ kids miss out. Ie the water can become too saturated with the chemicals and limits the amount that stays in solution. So even on an atomic level you can have too much of a good thing, so over fertilizing is a wasted effort. The number of kids that can join in is also affected by pH and temperature which is also something to take into consideration when feeding your plants.
Ok so you have these chemicals – now molecules, which are groups of chemicals joined in a way that makes them able to join in with the water chemicals to become soluble, sloshing about in the soil. Well not quite sloshing because as all things have this electrical charge, either positive or negative, then the chemicals are hanging around with the soil chemicals and the water chemicals attract them over and like hanging off monkey bars in the playground they swap one rung for another. The root hair can’t take on soil particles but can take on water. But how?
Ok – I don’t know about you, but I need a break here. I don’t enjoy chemistry and I’m sure my old science teacher would look at my explanation and roll his eyes – but I’m not sitting an exam here and a vague understanding of the horrible bits is good enough for me. But we are safely through that bit and how the nutrients get in is kind of cool – once you know about the horrible bits.
Come again soon – for the actual how it gets in. I hope this is making sense to you.
Sarah the Gardener : o)