But what if there were insufficient calcium in the soil – how can this addressed? By liming i.e adding lime to the soil.

Lime is usually added to the soil to raise its pH, to increase the alkaline balance of a soil. This is especially true of sandy soils where rain and water wash easily through, taking or ‘leaching’ nutrients with them. Calcium is what makes a soil alkaline.

And calcium is introduced into the soil in the form of lime. ( It helps at this point, to disassociate any links your mind might make to small, green, citrus fruit, think instead of those limes as ‘red herrings’ in this context.)

And calcium is also the nutrient needed to build a  plants’ cells – and if cells are properly built – BER doesn’t occur.

In this day and age useful (and not so…) products come with catchy and solution-orientated names. So lime, with its simple (and pH misleading)  name is a bit of mystery. Here I try and decode it. It starts with quarried chalk or limestone. And then becomes :

Calcium carbonate – ordinary lime (CaCO3).  Ground to a fine powder and variously referred to as: garden lime/carbonate of lime/ground limestone/ground chalk.

Quicklime or burnt lime – calcium oxide – chalk or limestone heated in a lime kiln.

Slaked or hydrated lime – calcium oxide – treated with water, making it calcium hydroxide.

But no matter how treated, all limes revert to calcium carbonate when incorporated into soil.

Dolomitic Lime, slightly different, in that it is ground from quarried rock and in addition to calcium contains magnesium.

So all these limes raise the alkalinity of the soil and are a source of calcium. One thing not to do though is apply any kind of lime to the soil at the same time as incorporating manure. They react with each other and result in valuable nitrogen being lost (from soil to atmosphere) in the form of ammonia.

The process of the loss of water vapour from a plant through its leaves into the atmosphere is transpiration. It’s transpiration and the transpiration pull which are responsible for the gravity defying movement of water from the roots of the plant to its very upper most parts – no matter how high rise they might be.

The water which exits the leaves as vapour is replaced by water which enters the plant via its root system. Water vapour leaving the plant creates a tension which results in liquid water being pulled up through the plant in an unbroken column of water. This is the method by which water and waterborne nutrients are circulated round the plant.

There is also control system to ensure the volume of water being absorbed by the roots remains in balance with the volume of water being lost as vapour. This control is maintained by a pair of guard cells which sit at the entrance to the stomata. If too much water is being lost through the leaves then the guard cells react, which results in the closure of the stomata. Which halts the diffusion of water vapour into the atmosphere.

So water in, water vapour out. Transpiration provides a plant with its ‘self watering’ mechanism at the same time as creating a lovely cooling effect on the leaves themselves.

This week it’s the ‘and what happens then’ -  Respiration – which is easier to understand when referred to by its longer title of cellular respiration (as the muddle with ‘and how does it relate to breathing’ doesn’t then need to be had).

As with photosynthesis, respiration is a process which takes place in the cells of the plant. But unlike photosynthesis, it’s not limited to one group of cells, instead it’s all living cells, of all tissues. And it’s a continuous process, taking place in darkness and in light.

The exact spot within a cell is within an organelle – the Mitochondria.

Photosynthesis creates food. Cellular respiration extracts the energy from this food. The plant uses energy for production and to fuel certain activities; the production of structural substances such as cellulose, proteins to form enzymes and the fuelling of activities such as cell division and chemical reactions which occur within the cells themselves.

The process itself involves the oxidisation of sugars; the combination of the food sugars with oxygen. The sugars are broken down, resulting in the release of energy and carbon dioxide and water as by products.

So sort of the opposite of photosynthesis…. and at the same time… a virtuous circle….

Revisiting it, there seem more elements to grasp. Here’s my attempt at conveying the basics in a fashion more suited to Jackie magazine ( my favourite reading at the time) than textbook ( not).

The Photosynthesis Party

Venue: Chloroplast. To find a chloroplast, go to a palisade mesophyll cell.  You’ll find them near the surface of a plant leaf.

Once in the cell there will be 50 to 100 chloroplasts to choose from – don’t worry - they all hold the same party so you can’t pick the wrong one.

Main Man: Chlorophyll. To stay the course he’ll have been keeping up his mineral intake. Too little iron or magnesium and he’ll miss out on the photosynthesizing action. He’s not forgotten the time when looking yellow around the gills, he was diagnosed chlorotic and the whole thing went ahead without him.

Star Guest: Sunlight. Brings the party to life, all that energy. But Chlorophyll’s got his favourite parts of this guest’s spectrum suit of many colours, greens and yellows he reflects right back out again whilst holding blues and reds hostage.

Time: Starts in daylight hours, scheduled to continue all night long.

Action: With the arrival of light, chlorophyll gets excited and rejecting all others, corrals his beloved red and blue into the VIP area. Meanwhile water, a photosynthesis regular, is trying his luck and has turned up as a double act – hydrogen and oxygen. But at this bash, which is different from the respiration party, only hydrogen has an access all areas pass. A scuffle breaks out and with all the energy from the arrival of red and blue light still buzzing around hydrogen gets separated from oxygen. So whilst hydrogen stays, oxygen exits the leaf and slips quietly away into the atmosphere.

Later another guest, Carbon dioxide, who’d arrived earlier in the day when it was still light, decides its now or never. He’d seen hydrogen arrive as part of water but didn’t want to make his move with oxygen still around. Now, under the cover of darkness he seizes his moment thinking, united with hydrogen, life will be sweet.

He gets his friend, enzyme ribulose bisphosphate carboxylase, to make the introductions, who despite his long name makes short work of bringing them together.

‘Who’d have thought it‘…. he said….. ‘carbon dioxide and hydrogen‘… but everyone misheard him and thought he said ‘carbohydrate’ and so that’s how they came to be known….

Not perhaps a technically accurate rendition of photosynthesis but I thought I’d give myself a little more poetic license than 

• 6 C20 molecules + 6 H20 molecules plus light give rise to 1 C6H12O6 molecule + 6 O2 molecules ( when in the presence of chlorophyll)

allows for !!

What is humidity?
Water vapour held in the air. Given we can feel but not see it vapour in the air is measured by hygrometers and calculated by hygrometric tables.

The quantity of water vapour that air can hold depends on the temperature of that air.

• The lower the temperature of the air – the less water vapour it can hold
• The higher the temperature of the air – the more water it can hold

When the maximum amount of water vapour for a given air temperature is reached then that air has reached its Saturation Point.

If air reaches Saturation Point and then the air temperature subsequently drops, the ‘excess’ water vapour it can no longer accomodate has to be dumped. This is achieved by condensing it into water – the liquid version !

In an interior situation this creates that irritating phenomenon – condensation. In micro, on the inside lid of a propagator – or on a larger domestic scale, on the inside window panes.

Outdoors; clouds, fog and mist are the result of water vapour ‘converting’ to liquid.

And Relative Humidity – well it’s all relative, see……relative to the air temperature……
Relative humidity is the % of water vapour that the air can hold at a certain temperature. The water vapour in the air is measure by grams of water vapour per kilograms of air. But then it expressed as a % of what the maximum amount of water vapour air of that particular temperature can hold. With warm air being able to hold a greater maximum amount of water vapour than cold.

And to go back to blight and its relationship to humidity – it would seem it doesn’t get out of bed for anything less than 10C and 90% humidity over the period of two consecutive days. So when us tomato lovers feel sticky and out of sorts for a couple of days on the trot - it’s because we sense something nasty is stirring and coming to life……

The tomato is a Succulent, Berry fruit. Translated this means fleshy and containing lots of seeds. Seems accurate enough.  It’s also classed as a Simple fruit; this means each flower bears only a single ovary.
It’s the ovary which grows to form the mature fruit. The ovules within the ovary form the seeds.

The purpose of the ovary is to protect the seeds. In time the fruit ripens and is either eaten by a dispersal agent who digests and passes the seeds (that’ll be the squirrels who live in the trees at the bottom of the garden who must have a giant tomato patch somewhere based on the amount of digesting they managed last year) or breaks down around the seeds, leaving them exposed. This is known as an indehiscent action. This allows the seeds to germinate and begin the  process all over again.

I think Elton John may have even been moved to pen a song about it all…

We might worry seedlings won’t come up. But the thing we don’t give thought to is the notion they might come up the wrong way. Roots waggling above ground like legs of an upended can-can dancer and leaves groping their way through the darkness of the soil like a lost Alice.

The reason for this – Geotropism; a plant’s response to gravity.  Roots go down, shoots come up.

The root is positively geotropic meaning it grows in the direction of gravity.
The shoot/stem negatively geotropic; it grows opposite to the gravitational force.
This means the plant always gets its survival mechanisms the right way round. Roots go down for water; leaves come up for light.

All this happens regardless of the seed’s position when it’s sown. Imagine it being up to us to position it correctly…. rotate right, rotate left, up a little, down a little. Given all life is sustained by plants – it’s a good job seed has its own built-in weeble processor and doesn’t need to rely on our evolutionary Golden Shot wielding ability.

After all, I still sometimes find myself at the stage of wondering why the words ‘ open this way up’ have been printed upside down, realising only where the real error lies, when the box’s contents, in a positively unhelpful geotropic manner, hit the floor.

Photo by BlueRidgeKitties

They’ve been through a process known as epigeous germination. This specifically refers to the process where the seeds leaves (cotyledons) come up and unfurl as the seedling emerges into the air. The role of the seed leaves is to provide the plant with stored energy until it can start making its own – through the process of photosynthesis.

All seedlings need this initial source of stored energy to draw on but with some, like the pea, the cotyledons don’t emerge with the seedling but remain under the soil. This other type of germination is known as hypogeous.

So small and yet already so perfectly formed and ingeniously designed !

These little fellows are doing what comes naturally. Positioned indoors besides a window, they grow towards the light. For them light is everything, for with light, comes photosynthesis and from photosynthesis, energy. The name for this response – phototropism.

If they were outdoors and the light falling evenly on them from overhead they would be headed straight up, no stretching required. Conventional wisdom would have me turn them round so they ‘straighten up’ by bending back the other way. Indeed last year I spun my young tomatoes so frequently they must have thought life a veritable carousel.
BUT
It would seem there are downsides to this approach – all to do with the plant hormone, Auxin. Auxin stimulates an increase in the length of plant cells.

Auxin is present on the shaded side of a stem and so its presence and effect is to cause the shaded side of the plant stem to elongate. If the plant is then turned round, to face the other way, Auxin will move across to the ‘new’ shady side causing that side of the stem to become elongated as well.

All of which will result in an elongated stem and we all know what we desire in a tomato plant is not leggy but stocky, sturdy even ….

I think it’s time to get out the silver foil and create a dazzling screen with which to reflect back all that light, so that no plant of mine shall start out on the shady side of life.

(A quick PS - there’s going to be an unexpected break in TL blogging and so I’ll be back here in just over a week.)

Shake a tomato seed into the crease of your palm and it’s difficult to imagine how,within a few months, it will become a strapping plant producing fruit and seed of its own.

So what’s in this tiny package and how does tomato life begin?

Essential features of the seed are embryo and testa.

The embryo is the tiny ‘plant in waiting’; the testa, the seed coat which protects it.

The holy trio of the embryo are the radicle, plumule and hypocotyl.

The radicle is the first to emerge from the testa; downwards it goes to form the root.

Next to poke its way out – the hypocotyl. Aloft of which is the plumule which will develop into the shoot system.
Emergence is often a little white loop, like a sowing stitch. This is the hypocotyl and by being the first to break the surface and pulling the plumule along behind, it protects the precious plumule from damage during this journey from underworld to light. The hypocotyl is also the connecting part between root and shoot.

In anticipation of this red carpet arrival I’ve been practising my ‘Hello hypocotyl and how lovely to see you’ve brought plumule along with you’.

Well if you’re going to talk to your plants I guess it’s never too early to start !