The weather was cold, wet and very windy in turn last week, disrupting many of my plans to get outdoors.  I had to cancel Monday’s trip to the Botanic Gardens because of heavy rain but did take a small group of students there on Tuesday, to show them how land plants have evolved from tiny mosses and liverworts to huge trees, using examples from around the garden.  I do think it is the only way to really make sense of plant life cycles which alternate between two very different multicellular generations – a haploid gametophyte (which produces eggs and sperm, each with a single set of chromosomes) and a diploid sporophyte (with the standard two sets of chromosomes produced after fertilization). 

Showing an image of the cycle is all very well but it makes much more sense with the plants in front of you. The students who came with me asked lots of pertinent questions and now have a really clear picture of how the balance between different parts of the cycle altered as land plants evolved to fill increasingly diverse ecological niches, further from standing water.

The basic story is that the haploid gametophyte stage decreases in relative size and the diploid sporophyte increases, during the course of land plant evolution.  In the bryophytes (mosses and liverworts), whose predecessors first appeared on land some 500 million years ago, the ‘plant body’ is the haploid gametophyte. A short-lived sporophyte, produced after fertilization and consisting of a spore-producing organ on a stalk, is the only diploid part of the plant.  The sporophyte produces the spores which will, in turn, grow into the next gametophyte.

By the time the ferns and horsetails appeared, around 70 million years later, a switch had taken place.  Now the fern itself is the diploid sporophyte and the haploid gametophyte is the transient stage.  When a fern spore germinates, it produces a tiny, heart-shaped gametophyte where fertilization takes place.  The sporophyte which grows as a result is much larger and quickly becomes independent of the gametophyte, developing its own roots and conducting tissue, and the gametophyte withers away.  The fern then goes on to produce spores on the underside of its fronds or leaves.

When the upstarts which become the flowering plants appear on the scene, only 150 million years ago, the gametophyte generation has shrunk so much that it only exists with in the dominant, sporophyte plant.  Most of us are blissfully unaware that pollen grains are actually the male gametophyte, rather the gamete itself, and that the female gametophytes is reduced to an embryo sac within the ovule!

Of course this is not the best time of year to find plants in flower, but the mosses are thriving now that most of the trees which shade them have lost their leaves. We’ll come back in the spring when there are more flowers to see.

A workshop on research methods for plant science later in the week in my level two module got me thinking about how we can get students to see earlier in their degrees how crucial plant research is. Talking to Marc, who did the same degree as me, we recalled a lecture series by Don Boulter on ‘Economic Botany’, including the evolution of key crop plants, which had inspired both of us.  That seemed to me a good enough reason to try and squeeze in another first year lecture on how the flowering plants, in particular, have been modified by humans for millennia to improve their value to us as crops.  I’m very good at generating more work for myself!

My free time last week was largely spent with Harry at his new flat, painting madly to get it looking more like home, so there was no time for the allotment.  With two bedrooms and the large, south-facing living room now mostly finished, I think it’s mission accomplished!  He’s just ten minutes walk from the sea front at South Shields so on Thursday we took our sandwiches down to eat overlooking the beach.  On Saturday, with Storm Darragh in full swing, that wouldn’t have been much fun! We’ve had Harry’s cat staying with us while he has been moving and settling in and she’s gradually become braver about venturing into the garden and turns out to be particularly adept at darting out the door as I am in the process of leaving and then sheltering in the most in accessible place.  The upside of that is that, while trying to bribe her back inside with cat treats, I spotted Wallflowers, Japanese quince and snapdragons in flower, in a sheltered spot at the front of the house.

The week’s cultural highlight was seeing Conclave, the film of Robert Harris’ book set in the Vatican at the time of the election of a new Pope.  Ralph Fiennes is brilliant as Dean Lawrence, the man tasked with managing the highly political conclave, when more liberal cardinals are facing a backlash from their traditionalist colleagues.  There’s a thought-provoking twist in the tail when an unfancied  candidate is finally elected after a stirring speech given in the immediate aftermath of a terrorist bomb, “The church is not tradition. The church is not the past. The church is what we do next.”

This week I’ve been reading Piranesi, by Susannah Clarke. The other world in which most of the book is set is described beautifully, but I did find the book a bit baffling to start with. However it was worth persisting – the unravelling of the mystery of how the eponymous Piranesi ends up in this parallel world is a gripping read.