Three words we always relish on the National weather forecasts.
The weather has picked up, the days are rapidly lengthening, and 5 days ago a high pressure system drifted across the UK from Scandinavia. So I finally managed to see and photograph both bumblebees and honeybees in the garden, one of the great spring markers, on March 10th…
We’d been kept going and cheered not just by all spring flowers, but also by that sublime early season songster, the thrush (mistle or song, anyone?) which always chooses a prominent tall tree around the property and valley below to try out it’s repertoire in repeated phrases, 3 or 4 times, before moving on. It’s range is enormous, and it can easily keep it up almost none stop for 15 to 20 minutes at a stretch…
On a calm day the clear tones travel huge distances, particularly if it’s facing you. But they’re understandably quite wary of close approach, having telegraphed their location so clearly to potential predators, so the photo above is with the Camcorder’s 30X zoom, and lacking real clarity. Such a shame I can’t easily upload the video clip – a brilliant stress busting 4 minutes to enjoy, of beautifully clear song.
The general lack of sunshine (and bees) in February/early March has presented very few occasions on which even I have been able to pollinate Crocus flowers. This should have meant that the display lasted a little longer than most years. But this wasn’t the case, the terrace display of C.tommasinianus fizzling out just as I expected it to improve. I then got up close, to study the individual Crocus plants, and noticed the tell tale signs of rabbit and mouse, vole, perhaps even rat, damage. And that all we’re left with here are the flowers of the sterile cultivar, C.t “Ruby Giant”, above. The other planted forms of C.t. “Whitewell’s Purple” and C.t. “Barr’s Purple”, together with my seed grown forms, have almost no flowers remaining.
Rabbits are pretty unselective, and graze off both leaves and flowers – not so good for Crocus performance next year, but typically take out those which are easiest to access, such as beside the path along our daffodil walk. My strategy now is to plant individual snowdrops, which are unpalatable, amidst such easy to access Crocus clumps.
By contrast rodents seem to be much more particular, and take the flower off at the top of the pistil (stem) just beneath the petals’ (or more correctly tepals’) base. Too late in the year, (i.e. last night!) I realised that I could try to photograph such nocturnal mayhem, but this may have to wait until next year.
I do however have a daytime image from my very first blog post of a vole attacking the flowers in 2011, so I’m revisiting old territory. Click here. But this year I started to become aware that the flowers didn’t seem to be taken by the rodents until I’d been round with my pollinating brush. If that is the case, it would perhaps preclude the possibility that the rodents were after either pollen or nectar – wouldn’t they then have taken flowers out earlier?
This might just be a coincidental observation. Maybe the conditions in which I can wield my brush (i.e. slightly warmer and sunnier) actually boost nectar secretion, or pollen release by the anthers? But surely such a boost would be temporary as flowers closed, and cloud or cold returned?
But there were several clumps of Crocus forms unique to Gelli, in that they were the result of me scattering saved, and probably even hand pollinated, seed a few years earlier, which within 48 hours of my pollination, had nearly all their flowers eaten off.
This could be viewed in 2 ways. Firstly, a natural form of dead heading, which by avoiding seed formation should allow the plants to put more energy into new corms and flower buds for next year, so producing an even better display in 2017!
Or secondly, extremely frustrating because my pollinating efforts will have been in vain, since no seed will be formed. Our variants on Crocus chrysanthus “Snow Bunting”, never seem to suffer in the same way from rodent flower predation, and the flowers just fade gracefully, leaving a long term, en masse display. They anyway set very few seeds eventually, regardless of my, or natural, pollinator efforts.
But does seed formation actually suffer after such flower predation ? As I discovered in my very first blog, in the Crocus flower the ovary, developing ovules and subsequently seeds, are located below ground level. So the question is how long does it take the pollen grain to germinate, grow down the flower’s longish pistil and achieve successful fertilisation?
Things now become a bit murky. Whilst I discovered that in maize plants, a pollen grain can germinate and extend it’s pollen tube by a foot within 24 hours, I couldn’t track this information down for Crocus flowers. Although the distance to be travelled to reach the Crocus ovary is much shorter than in maize, the temperatures are much lower at this time of the year, so one might expect slower growth. (The flower below is a gorgeous rose pink – another result of seed saving from hand pollination efforts) …
But what about about the nipping off of the top section of a partially growing pollen tube? Will this ‘kill’ the structure, and prevent it ever reaching it’s destination? Again I couldn’t find an answer, though it’s presumably known.
Firstly, the very formation and release of pollen grains from within the developing anther involves a complex sequence of co-ordinated cellular changes, including the concept of programmed cell death, to allow anther splitting or dehiscence. Click here for some electronmicrographs on anther structure, and more…
Secondly, pollen grains from insect pollinated, or entomophilous, flowers are coated with a special substance known as pollenkitt. What an interesting word! This seems to have lots of potential properties, but in particular makes the pollen grains stickier and more likely to cling onto the hairy body of a visiting insect. Apparently the most useful pollen, from the flowers’ point of view, is not that which honey and bumblebees collect onto their leg pollen baskets, or corbiculae, but rather the loose grains sticking to body hair.
Thirdly, when pollen gets transferred onto the tip of the stigma, in flowers that are self incompatible, the grain can recognised as coming from the same flower, and pollen tube growth is inhibited. If it’s from a different flower, germination of the pollen tube is encouraged. How sophisticated…
And then a host of biochemical changes encourage and direct the pollen tube’s growth down the pistil, to guide the tip of the tube towards the ovary (below ground, in the Crocus), rather than wandering around aimlessly in it’s growth, and never getting anywhere near the ovary. The biochemistry involved in this is now quite well understood, and, not surprisingly, amazingly complex.
But 2 factors are key. Firstly at the very growing tip of the pollen tube, there is a dramatically increased concentration of Calcium ions which gives a directional cue to its growth. Secondly actin filaments and myosin motors control the tip’s growth.
This was real news to me, since I remember from years before that these compounds are vital components of animal’s muscle fibres. (Maybe the voles are after a pseudo carnivorous fix, rather than a mere vegetarian hit?). The modified image below hints at all this complexity. ( From a review article by Alexander Krichevskya, Stanislav V. Kozlovskya, Guo-Wei Tianb, Min-Huei Chena, Adi Zaltsmana, Vitaly Citovskya – Click here for more from this paper), and here for more on actin (and myosin).
But behind this rapidly lengthening pollen tube tip, something else really interesting is happening. 2 separate sperm cells, or gametes, are tracking down this elongating tube, just behind the tip. When the pollen tube tip eventually reaches the ovary, one of these sperm cells fuses with an egg cell to form the embryo seed, or zygote, whilst the other sperm cell fuses with 2 separate female derived cells to form a 3 celled structure, which goes on to create the endosperm, or food structure, that accompanies the developing seed embryo. The endospem is vital as the food store for the seed’s subsequent successful germination. So there really is a double fertilisation going on, in all endosperm flowering plants. Click here for more on this, including some great diagrams to illustrate what I’ve tried to describe here.
So if the rodent chompers nip through the pistil – and pollen tubes, after their tip’s and sperm cells have already grown a significant distance past the point of severance damage, are they still viable? I’m going to mark a couple of chomped Crocus clumps to see if I can count the number of seed pods being pushed up towards the end of June, but I guess the definitive answer to this issue would involve cutting through pistils manually, at differing times after pollination, and seeing whether seed capsules do still subsequently develop – an experiment for next year, I think..
In late February, we had another couple of severe frosts, so I’d nipped out just before bed to check on our blue bowl. No signs of an ice spike forming, but by torch light, held at just the right angle, one could make out planes of ice crystals growing down into the freezing water – already covered with a thin surface ice sheet, which by dawn had fissured in an interesting way, above. I had a go at photographing these ice crystal sheets, rather crudely with my hand held torch since I don’t have an off camera flash, and head on flash completely obliterates the visibility of the thin crystal sheets…
Not hugely impressive photos, but maybe sufficiently interesting to inspire someone else to look into freezing water at night, to glimpse what’s going on. I also tried a hand held time lapse, which didn’t show significant crystal enlargement in the short time I could manage to hold my camera and torch positions. Just 15 seconds of 1 second frame exposures seems a heck of a long time when stock still in the cold! However, it did show quite dramatic sub-ice water movement currents, highlighted by particulate debris shifting around below the surface ice. But I was also then sent 2 pictures of an ice spike and ice vase by friends from just across the valley, which encourages me to stake a claim for Rhydcymerau as being an ice spike hot spot.
Or should that be cold spot? (Thanks for the great pics, Gary). Amazing structures.Gary is also a talented wood turner/artist. Click here for a link to his website at wobbly bottom…
Less enjoyable nocturnal action came last week in the shape of a visiting bat, which somehow or other found a way inside, and then, as they do, attempted to escape from our bedroom shortly after lights out. Having a low, sloping ceiling means that frequent passes were so close to our snucked down heads, that you could feel the air movements from it’s beating wings. Having thought I’d trapped it downstairs, and, after grabbing my camera, it somehow reappeared in the stairwell and as I crouched low, fizzed over my head into the other end of the house.
I slammed the door. We returned to bed untroubled…But the following night’s supper was enlivened by Fiona’s screech as it did an encore pass over our heads and dinners, before we opted to suffer a chilly evening and leave the front door open.
Finally the verdict. Some liked the BBC2 ‘s Gardener’s World feature on Gelli Uchaf, others felt there weren’t enough garden scenes, or chat with us… Personally we thought a great job was done, given the weather, and the fact that filming took place on February 9th. The atmosphere of the garden was definitely captured… Of course if they’d filmed this week, 4 weeks later, there were lots more flowers in the garden, but there is still the challenge of capturing the effect of en masse low growing small flowers, which I too struggle with…
And often require you to lie prone on the ground to get any sense of how many flowers there are. If you do this, and take this low angle vantage point, then it’s well nigh impossible to include a presenter or gardener in the scene as well. Or certainly not in a favourable way…So hats off to the team for what they achieved. And even better that they chose February 9th and not last Wednesday…
If they had, there could well have been fatalities, as a significant branch was ripped off the Oak tree by a violent wind gust from the North and smashed into the slated barn roof, before coming to rest where most of the crew had been standing during some of the filming…
This tree definitely has previous form. I was once nearly skewered whilst removing an even larger ripped off branch which had embedded its peripheral twigs amongst the azaleas, with it’s base barely hanging on by it’s splintered remnants, a good 10 feet up in the air. After carefully chainsawing the outer branches off, I reached the last one which, whilst still embedded in the ground, was preventing the severed base from tearing away from the trunk… Anticipating that removing this branch would destabilise the whole thing, I was still shocked to see the complete 14 inch thick branch flip over in mid air, and the jagged pointed base head towards me at alarming speed. I thought I had dodged it, but at the last moment it readjusted its direction, and I had to drop the chainsaw before diving to the side to avoid being impaled.
Serenity has now returned, the daffodils are trumpeting, the kites mewing and circling with their extraordinary sophisticated forked, ruddered tails driving lazy, wind driven recce flights overhead, with scarcely a wing flap.