We may not have the same jobs as you, but our life is busy too.
I don’t work a 9–5 job. I don’t take the bus or metro either. I live a rather peaceful life outdoors, motionless. I drink the water and minerals from the ground and open my little mouths to eat the sun and carbon dioxide. Easy life, right?
Well, not exactly.
During the day, like all trees, I meet challenges as my environment changes following the course of the sun. I am very sensitive to changes in sunlight, air humidity and temperature.
Coffee trees like me need three elements to thrive. Each of them plays a key role in my plant’s life and well-being.
My day begins the moment the Sun sends its rays over the horizon. You’d think I just sit and soak in the rays, but actually I have to do a lot of work to get started.
And, there’s no ‘snooze’ button for the Sun.
Light, or more specifically the blue and red lights, are what make me wake up in the morning. You can think of them as my alarm-clock, although the technical term is “photosynthetically active radiation”. Morning-time is low-sugar time. I’ve just survived a whole night without sunlight; a night of sugar getting used up and none getting replaced. So, I open my stomata wide, drinking in the sunlight-giving energy.
Did I mean to say “stomach”? No: stomata are more like tiny mouths on my leaves. Little holes not visible to the naked eyes, that plants use to breath and capture carbon dioxide. I close and open them depending on the environmental conditions around me.
But why light at all? Well, it’s the source of energy that I use to…make energy.
Specifically, I photosynthesise sugars. “Photosynthesis” is a complicated process, but it basically involves capturing water and carbon dioxide, cutting them into pieces with the energy of the light, and merging them together to make sugar or carbohydrates.
Sugar and carbohydrates are my main energy stores — and yours too, in fact.
So, open stomata in the morning and I’m done. Right?
Well…no. I don’t have a nice AC-cooled office to work in; my workspace is directly exposed to the elements. There comes a time of day when the Sun becomes not a friend but a foe.
They say ACs tend to dehydrate a person, so humans working in air-conditioned rooms should remember to keep drinking water. ACs, however, are nothing compared to the hot midday sun. This is when stomata start working the other way round. While taking sunlight in, they also end up letting water out. Not good!
Like humans, I need water to live. Living organisms are actually mostly made of water. It’s the medium in which my chemical reactions can happen. Photosynthesis, for example, happens in water. In the form of sap, water flows through plants from the roots to the leaves. It brings minerals to the top, and sugars to the bottom.
The sap of the coffee tree is like the blood of human beings. My sap transports all vital elements to help me live happily. Without it, I would wilt and die.
What this means is, I can’t afford to let so much water escape into the air. During midday, when the air gets hot, I close my stomata.
This doesn’t mean losing water is always a bad thing. Water escaping is only the final stage in “transpiration”, where water from the bottom of the plant slowly rises up and out into the air. You can think of it working like in a giant straw, except there’s sun-evaporated water drawing the rest out instead of a pair of giant lips.
Transpiration causes plants to lose water, but it’s also vital to maintain a good flow. As the water travels up, it also carries nutrients up from the ground and through my organs. I must be careful to not lose too much water, while staying active and photosynthesising.
Like many things in life, it’s a trade-off.
During hot and dry days, I am especially careful not to lose too much water. I regulate the amount of water I lose with my stomata. Opened, water vapour will go out and I will transpire water. Closed, I will save water but also stop photosynthesising as carbon dioxide won’t be able to enter my leaf anymore.
Now, in early April, is a great time for me: almost like having a holiday! The rainy seasons have just set in, and the air is hot and humid. Humidity means evaporation doesn’t happen so fast, since there’s already water outside, while the heat implies lots of light to photosynthesise.
I close my stomata around midday when it gets unbearably hot, but the rest of the time I open them wide to generate lots and lots of sugar.
You see, it’s approaching the time of year when I need all the sugar I can get.
Today is a special day for me. The skies have once again opened up with rain, and it’s time for me to start generating my first flowers of the season!
Up till now, the weather here has been very hot and dry. Rain always stops during that period, starting November and ending early March — although climate-change has made these timings more erratic and unreliable over the years. Regardless of time, whenever it’s dry, coffee trees like me rely on water stored in the ground to survive.
It’s like those “less customers, low sales” periods all companies dread, except that mine continues all through Christmas.
That doesn’t mean I don’t have winter holidays. The lack of water in the dry season, combined with its low temperature, pushes me to enter a more dormant state. Work doesn’t end for me, but it does slow down. My stomata are only moderately open, and photosynthesis is low: I’m not collecting much energy, and neither am I doing much with the energy I have. This is not as extreme as bears and their winter hibernations, but it’s the closest to that I’ll ever get.
At the end of the dry season, only a little water is left and I am very stressed. Which is why I’m happy to welcome the first March rain, and celebrate with a shower of flowers.
Leave that be. The hard months are now behind us, and I can look forward to the wet season. Weather will get very rainy now; it could rain all day for weeks!
Now you can guess why I go into overdrive. Most of my vegetative growth happens during the wet season, from April to October, when water is abundant and it’s hot all day and night.
Come mid-afternoon, when the heat goes down, I’ll open my stomata and make a lot of sugar to grow well. Throughout this season, I’ll also be growing my lovely fruits which are usually ripened and ready for harvest by the end of the year.
While we’re on the subject of heat, let me mention the two key roles temperature plays in my life. I mean, apart from the fact that it makes me open and shut my stomata when it’s too hot or not. I’m talking about more long-term roles here.
On a yearly basis, temperature influences the pace of my life. Have you ever felt slow and lazy on a cold day? I get that too. When temperatures are lower, chemical reactions happen slower, which means photosynthesis and energy levels go down too. Warm weather, on the other hand, races me up. It’s when I start blooming flowers, and putting out fruits, and generally growing faster, as I mentioned before.
It’s not just about seasons, though. At high altitudes, where the weather is colder, coffee trees grow slower too.
Temperature also influences me indirectly, by affecting the amount of water in the ground and the air. The higher the temperature, the drier the environment, both underground and above ground.
The humidity around me varies throughout the day. It’s very high at night, and low in the afternoon at 4 p.m. That’s why I close my stomata at 4, and open them early in the morning when the sun rises. As natural light starts to rise at 7 a.m, my stomata start to open so I can get carbon dioxide to photosynthesise.
In addition to the low levels of humidity in the afternoon, we coffee trees must also support high temperatures which dry the air.
My working day ends in the early evening, when sunlight gets too low for me to work. (Good thing bulbs are not an option for me). During the night, I close my stomata even though humidity is high, because what’s the point of leaving them open anyway?
Like all coffee trees, I enjoy my daily routine. It gets unpleasant and stressful at times, but overall there is something peaceful in opening and closing my stomata, and changing air and water into sugar. I also find comfort the course of the season that we, coffee trees, have been used to for generations.
Unfortunately, my peaceful routine is being disturbed by a global challenge: climate change. As temperature increases, the seasons shift at different times, and the water becomes scarce, coffee trees will have to adapt or die.
Will I be able to open and close my stomata at the right time to avoid the deadly effect of drought? Will my coffee tree friends survive storms? Let’s hope they will.
Otherwise your morning coffee-cup will become a memory. And, your morning routine will begin to change as well.