Plant Cuttings
Annals of Botany 112: iv–vi, 2013
Available online at www.aob.oxfordjournals.org
News in Botany: Nigel Chaffey presents a round-up of plant-based items from the world’s media
Want to save E320 billion a year?
Alarmingly, that is the estimated
upper limit of the cost of nitrate
pollution in Europe, much of which
results from use of nitrogen-based
fertilisers to overcome nitrogen
insufficiency in the soil for crop
growth[1]. A major problem
associated with over-use of nitrate
fertilisers on the land is water-based
eutrophication[2], specifically
human-caused cultural
eutrophication, which is bad news
for all of us, and something to be avoided if possible. Trying to
avoid such environmental damage – and maybe save some
money as well – by releasing plants from their dependence upon
externally supplied N compounds, a new technology aspires to
convert crops that don’t normally harbour N-fixing bacteria (such
as legumes[3]) into plants that can use the nitrogen that is freely
available in the atmosphere and fix it into compounds that the
plant is able to use[4]. The treatment – known as N-Fix and
developed by Prof. Edward Cocking (Director of The University
of Nottingham’s Centre for Crop Nitrogen Fixation) – exploitsthe
ability of a specific strain of N-fixing bacteria found in sugar-cane,
Gluconacetobacter diazotrophicus [5], that can colonise cells of all
major crop plants. The technology has been licensed by The
University of Nottingham to Azotic Technologies Ltd[6] and is
delivered as a bacterial coating to the seeds. Importantly, it is
stressed that the process is neither genetic engineering/
modification (GE/GM) nor ‘bio-engineering’. Rather, N-Fix is
seen as a natural seed coating that provides a sustainable solution
to fertiliser overuse and nitrogen pollution, is environmentally
friendly and can be applied to all crops. Does this sound too good
to be true? Well, 10 years of a series of extensive research
programmes have established proof of principle of the technology
in the laboratory, growth rooms and glasshouses. If this can be
scaled up to sustainable levels in the field, this application has
enormous implications for agriculture as the technology could
provide much of the plant’s nitrogen needs, reducing costs – both
monetary and environmental – of expensive synthetic nitrogen
fertiliser. Still, one wonders how widely available – and
affordable – these seeds will be to those farmers in the poorest
areas of the planet most in need of such an N-Fix.
[In addition to the press release’s associated video, for more on the
science and potential of this fascinating story, try Cocking et al.’s
‘Intracellular colonization of roots of Arabidopsis and crop plants
by Gluconacetobacter diazotrophicus’[7], Raúl Pedraza’s ‘Recent
advances in nitrogen-fixing acetic acid bacteria’[8], Ted Cocking
and Philip Stone’s online poster ‘Mitigating increases in nitrogen
deposition’[9], and the ‘Complete genome sequence of the
sugarcane nitrogen-fixing endophyte Gluconacetobacter
diazotrophicus Pal5’ by Marcelo Bertalan et al. [10] – Ed.]
[4]
http://bit.ly/19KmN9I; [5] http://bit.ly/14fVAYs;
http://bit.ly/1b8ErSC; [7] In Vitro Cellular and Developmental Biology Plant 42: 74 – 82, 2006; [8] International Journal of Food Microbiology
125: 25 – 35, 2008; [9] http://bit.ly/1eprjbh; [10] BMC Genomics 10: 450,
2009.
[6]
Reaching the masses: true botanical evangelism
I don’t know what the average enrolment on a first-year
university plant science course is, but I can guess that it isn’t
more than 5000. But 5009 is the number who had signed up to
Prof. Daniel Chamovitz and Aviva Katz series of ‘classes’
intriguingly entitled, ‘What a Plant Knows (and other things
you didn’t know about plants)’[1] by 3.14 pm on 20th July
2013. That number of students won’t fit into a single lecture
theatre, nor even a single campus, but is comprised of individuals
throughout the world who are taking the course via Coursera,
‘an education company that partners with the top universities
and organizations in the world to offer courses online for anyone
to take, for free, and whose technology enables our partners
to teach millions of students rather than hundreds’[2]. The
instructors are both based at Tel Aviv University[3,4] and the
course is based on Chamovitz’s recent book What a plant
knows [5], backed up with basic biology information found in
Campbell Biology [6]. The course runs for 7 weeks from 1st
October 2013 and should occupy 7–9 hours per week (and is
FREE). You will learn how plants sense their environment,
and how scientists study plant senses, and be exposed to both
classic and modern experiments in plant biology, and may even
start to question what defines us as humans. Grades will be
based on quizzes (on the video lectures and reading assignments), and a final exam. So, what background do you need to
consider enrolling? ‘Curiosity about nature and our place in
the world’. Why should we be excited about this venture?
Because it is tackling in a most direct – and wide-reaching! –
way the pernicious cult of zoochauvinism (or animal
chauvinism, ‘the widespread tendency of biologists to consider it
more important to study and teach about animals than about
plants’[7]; ‘a bias for animals and against plants’[8]), which
contributes to the condition known as ‘plant blindness’ (‘the
widespread lack of awareness of plants and neglect of plants both
in biology education and in the general population’[7]).
Ambitious? Certainly! Does it do its job? We’ll have to wait until
the end of the course, but what a great initiative. More power
to the Israeli team!
Image: Charles Doussault, ‘A class in the open’, wood engraving,
approx. 1842.
[1]
Image: Franz Eugen Köhler, Köhler’s Medizinal-Pflanzen.
Gera-Untermhaus, 1897.
[1]
http://www.nine-esf.org/ENA-Book;
https://en.wikipedia.org/wiki/Eutrophication;
[3]
http://en.wikipedia.org/wiki/Legume;
[2]
iv
https://www.coursera.org/course/plantknows;
https://www.coursera.org/about;
[3]
https://www.coursera.org/instructor/chamovitz;
[4]
https://www.coursera.org/instructor/akatz; [5] http://bit.ly/187jdT8;
[6]
Reece et al, 2010, Campbell Biology, 9th edn, Pearson/Benjamin
Cummings; [7] http://bit.ly/14vPmGW; [8] http://bit.ly/1546AEy.
[2]
Relocation, relocation, relocation . . .
I was aware that light levels
can influence orientation of
chloroplasts within plant cells[1 – 3],
but the fact that their location can
also be affected by temperature
was new to me. Anyway,
Yuka Ogasawara et al. report
cold-induced organelle relocation
in the liverwort Marchantia
polymorpha, not only of
chloroplasts, but nuclei and
peroxisomes, too[4]. Recognising
that these organelle movements take place naturally in winter,
the team propose that it might somehow facilitate cold
tolerance in the plants. Intriguingly, however, mitochondria did
not ‘cold-relocate’. Given that chloroplasts, peroxisomes and
mitochondria are intimately connected via the process of
photorespiration[5], I wonder what effect increased spatial
separation of the latter organelle from the other two might have
on this important metabolic process . . . ? Nevertheless, further
study of cold-induced organelle relocation in what is now
probably the model species for this phenomenon is likely to be
of relevance to other plants. Brrr-illiant!
regard it may be of some significance that the tubules just
beneath the surface of the protoplast mirror the orientation of
the cellulose microfibrils of the adjacent cell walls’ (from the
article’s abstract [2]). Nowadays, after a further half-century of
study, elements of the plant cytoskeleton – especially
tubulin-constructed microtubles, actin-based microfilaments,
and cytoskeleton-associated proteins[3 – 5] – have been
implicated in many aspects of plant cell biology and continue to
provide fruitful areas of investigation. Many dimensions of
those new and emerging microtubule-rooted areas of study are
covered in the issue’s 12 review articles. And with titles such as
‘The role of the cytoskeleton and associated proteins in
determination of the plant cell division plane’, ‘Microtubules
and biotic interactions’, ‘Microtubules in viral replication
and transport’, ‘Microtubules, signalling and abiotic stress’
and ‘Cytoskeleton-dependent endomembrane organization in
plant cells: an emerging role for microtubules’, you begin to
appreciate the true nature of the debt owed to that original
Ledbetter and Porter article. But the best bit of all this? Each of
the dozen review articles and the Editorial by Peter Hepler,
Jeremy Pickett-Heaps and Brian Gunning are all . . . FREE(!).
What a great teaching resource! Thank you, Plant Journal.
[Whilst such intracellular, small-scale chloroplast movements
are fascinating, the ultimate large-scale, ‘chloroplasts-onthe-move’ story must be those integrated into the bodies of
sacoglossan sea-slugs, and which remain functional within
their animal host. For more on this fascinating phenomenon of
trans-Kingdom organelle relocation, see Sónia Cruz et al.’s
review article[6] – Ed.]
[A question for those who know more about such
things than I: why are microtubules still permitted to be
called microtubules, whilst microfilaments are almost
overwhelmingly termed actin filaments in modern scientific
literature . . . ? Is it because the corresponding term ‘tubulin
tubules’ would seem slightly silly? If so – and for consistency
(surely, an admirable scientific principle?) – why don’t we
go back to those simpler times of microtubules and
microfilaments? – Ed.]
Image: Kristian Peters/Wikimedia Commons.
Image: Frank Boumphrey/Wikimedia Commons.
[1]
[2]
http://bit.ly/196YGTo; http://bit.ly/11JBK76;
http://bit.ly/14vTHdd; [4] Plant, Cell & Environment 36: 1520– 1528,
2013; [5] http://en.wikipedia.org/wiki/Photorespiration; [6] Journal of
Experimental Botany, in press, 2013.
[3]
[1]
The Plant Journal 75(2), 2013; [2] Journal of Cell Biology 19:
239 – 250, 1963; [3] http://bit.ly/16rJ6Mp; [4] http://bit.ly/154GQro;
[5]
Wasteneys & Yang, Plant Physiology 136: 3853 – 3854, 2004.
Chloroplasts are how old???
Homage to a nanotubule . . .
Frequently, journals will devote a
whole issue to a particular theme,
maybe even to a single species (even
whole journals are seemingly
devoted to Arabidopsis thaliana . . .).
But rarely will they be devoted to a
single journal article. Well, such
is the power of ‘Ledbetter and Porter (1963)’ that the July
2013 issue of the Plant Journal [1] pays due homage to that
seminal publication. Why does L&B ’63 deserve this honour?
Simply stated, that rather modest paper, entitled ‘A
“microtubule” in plant cell fine structure’, virtually
single-handedly initiated a whole new area of plant cell biology
research – the role of the cytoskeleton, particularly in
connection with cell wall formation. Its trend-setting and iconic
status can largely be traced back to some of the most influential
‘throw-away’ comments ever penned, such as, ‘It is noted
that the cortical tubules are in a favored position to . . . exert an
influence over the disposition of cell wall materials. In this
It is widely acknowledged that
eukaryotic cells (you know, the
ones with a membrane-bound
nucleus and a variety of other
membrane-bound organelles; cf.
prokaryotes[1]) came to be so
complex by a series of ‘mergers and
acquisitions’ that saw a
prokaryote-like cell internalise other, smaller ‘cells’ to gain
organelles such as mitochondria and chloroplasts. That is the
essence of the Serial Endosymbiotic Hypothesis/Theory[2,3].
But have you ever wondered how long ago such events took
place? Well, Patrick Shih and Nicholas Matzke have done so on
our behalf [4]. Using ‘cross-calibrated phylogenetic dating of
duplicated ATPase proteins’ (which are retained by
mitochondria and chloroplasts and involved in energy
production in both), the duo’s results suggest that primary
plastid endosymbiosis (which eventually gave us plant cells)
occurred approximately 900 Mya (millions of years ago),
whereas mitochondrial endosymbiosis occurred around 1200
v
Mya. Interestingly, both authors contributed equally to this
work, and both were PhD students at the time[5]! I’d so like one
of the authors to have done the mitochondria work, and the
other to have been ‘responsible’ for chloroplasts; that would
make for a pleasingly symmetrical, modern-day parallel to
the 19th century’s Cell Theory[6], largely attributed to
Schleiden (‘botanist’) and Schwann (‘zoologist’). Way to go,
gentlemen!
[Please don’t construe Mr Cuttings’ comments about putative
parallels with Schleiden and Schwann to mean that only
animal cells have mitochondria, and only plant cells have
chloroplasts; plant cells contain both (yes, so they are better
than animals . . . )! – Ed.]
Image: Mariana Ruiz Villarreal/Wikimedia Commons.
[1]
http://bit.ly/16x5Hcb; [2] http://bit.ly/1c7nbAZ; [3] http://bit.ly/16rLx1i;
PNAS 110: 12355 – 12360, 2013; [5] http://bit.ly/154LENJ;
[6]
http://en.wikipedia.org/wiki/Cell_theory.
[4]
Say it with flowers . . . ?
It’s always pleasing to me to know
that mankind’s relationship with
botanics is a very old and important
one. Indeed, so important and
profound are these plant – people
interactions that floral tributes
accompany many of the most
significant events in a person’s
life, e.g. use of calla lilies (Zantedeschia aethiopica [1]) at
weddings to symbolise purity[2]. Frequently, however, these
associations are so ancient that their true significance or
meaning may be lost to us today. Such is the issue facing Dani
Nadel et al., who have unearthed possibly the oldest example
of the decoration of graves with plants[3]. Working with
Natufian graves that were created 13 700 – 11 700 years ago in
the Raqefet Cave at Mt. Carmel (northern Israel), the team have
identified the presence of members of the Lamiaceae (mint
family) – such as Judean Sage, Salvia judaica [4] – and
vi
Scrophulariaceae (figwort family). For the most part the plants
were identified from impressions made in the mud lining of the
graves, and from phytoliths (tiny siliceous, opal-like mineral
bodies produced by many plants[5]). Both of which are nice
examples of the use of plant forensics in archaeology. Whether
use of specific plants implied sophisticated floriography (the
language of flowers, a means of coded communication
through the use or arrangement of flowers[6]) is not known. But
even if that were the case, the puzzle then is to understand the
code to know what message was being communicated.
Unravelling that will take a little while longer, I suspect.
Nevertheless, this work certainly pushes back an
evidence-based date for examples of such intimate ceremonial
associations between plants and people. From saying it with
flowers to saying it to flowers now, and an ‘experiment’[7] being
conducted by Bents Garden & Home (a family-run garden
centre in Cheshire, UK). The Great Experiment – which has
attracted some sceptical commentary from The Geeky
Gardener[8] – is aimed to examine whether plants respond to
the human voice. The experimental design features six (so they
should be able to undertake some statistical analysis . . . ) plants
(species unspecified – which is not good publicity for a
business that provides plants to the public . . . ) that will be
‘loved’ with kind words and happy thoughts, whilst another six
plants will be subjected to ‘hateful’ conditions and harsh
words; all other conditions such as watering and fertilization
will be exactly the same. ‘The results will be announced soon’
. . . Hmmm, maybe something to keep quiet about . . . ?
Image: Júlio Reis/Wikimedia Commons.
[1]
http://en.wikipedia.org/wiki/Calla_lily; [2] http://callalilymeaning.org/;
PNAS 110: 11774– 11778, 2013; [4] http://bit.ly/14gvjcz;
[5]
http://en.wikipedia.org/wiki/Phytolith;
[6]
http://en.wikipedia.org/wiki/Language_of_flowers;
[7]
http://bit.ly/15KFoOP; [8] http://bit.ly/1b9bdD3.
[3]
Nigel Chaffey
E-mail: [email protected]
Chaffey N. 2013. Plant Cuttings, September. Annals of Botany 112(5):
iv– vi.