Cider bender
Question: In autumn 1994, I planted a Cox鈥檚 Orange Pippin tree alongside a
Bramley cooker. In autumn 1995, each produced a small crop of their designated
variety.
In autumn 1996, the Cox tree produced a few small Cox apples but the Bramley
tree produced slightly sour Cox lookalikes鈥攄uring apple-blossom time there
had been frost and gales.
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Can someone tell me what happened and what I can expect in autumn 1997?
Please don鈥檛 say Golden Delicious.
Answer: Many apple trees (the Cox being one) are diploid (have two sets of
chromosomes) and will pollinate other nearby apple trees provided their
flowering periods overlap. The Bramley is triploid (has three sets of
chromosomes) and produces very little usable pollen, so it is virtually
ineffective as a pollinator. It therefore requires two other diploids for its
own pollination and these also cross-pollinate themselves.
It could be that the Bramley鈥檚 seedling quoted in this question is not
actually a Bramley鈥檚 seedling.
James Richards
Cambridge
Pepper pot
Question: This question was first asked on the news group sci.botany, but
nobody answered it. Are New 杏吧原创 readers able to help?
When a pepper is cut open there is a space inside, but there are no gaps in
the pepper where air could get through. What is the composition of gases in this
space, and how did they get there? If a green pepper contains chloroplasts would
there be more oxygen and less carbon dioxide in a green pepper than in a red,
yellow or orange one?
Answer: The questioner is not quite right in suggesting that 鈥渢here are no
gaps in the pepper where air could get through鈥�. Like most other plant surfaces
the surface of a pepper or capsicum has stomata. These are orifices which are
controlled by a pair of special cells, the guard cells, to open or shut as the
plant requires.
They communicate with an extensive network of air spaces within the tissues,
without which the gas exchange required for both photosynthesis and respiration
could not take place.
The source of the air is, therefore, the atmosphere, via the stomata and the
intercellular air spaces in the wall of the fruit. All capsicum fruit are
initially green, with functional chloroplasts, so it is possible that there
could be some enrichment in oxygen from photosynthesis at this stage, but not
very much, because without gas exchange with the outside air there would be no
source of carbon dioxide for further photosynthesis.
When a capsicum ripens to a red or yellow colour the chloroplasts cease to
function and turn into chromoplasts containing fibrous deposits of carotenoids
and protein. At this stage photosynthesis has ceased and the internal gas will
be unlikely to differ very much from the outside air other than in water vapour
content.
Guy Cox
Sydney, New South Wales
Answer: As the pepper develops, the gases from the atmosphere diffuse into
the capsicum鈥檚 growing cavity. The composition of the internal gases will depend
on the respiration rate of the pepper as well as the resistance to gas
diffusion. Generally, the more immature the pepper, the higher the respiration
rate of the tissues.
We decided to test the internal gas composition of different coloured peppers
in our laboratory using gas chromatography. The mean percentage levels of oxygen
and carbon dioxide respectively were: green (19.85, 0.068), yellow (18.45,
1.08), red (18.36, 1.15).
It is possible that the higher oxygen/lower carbon dioxide levels in the
green fruit were due to photosynthesis because the lab bench was in bright
sunshine during all the measurements.
Normally, however, internal light levels are much too low to support any
significant photosynthesis in harvested produce.
Julia Aked and Allen Hilton
Silsoe, Bedfordshire
Zeus juice
Question: What chemicals or substances are used to keep the Olympic flame
burning on its way to the Olympic stadium?
Answer: The Olympic torches used in the 1996 Summer Olympics held here in
Atlanta used propane gas stored in canisters in the handle.
Terry Blanton
Atlanta, Georgia, US
This week鈥檚 questions
Happy returns: Why do boomerangs come back?
Adam Longley (aged 6)
Barry, South Glamorgan
Yellow fever: How does the skin magically appear on top of the custard? I
really love it.
Freddie Coleman (aged 8)
Bournemouth, Dorset
Forecourt fear: My mobile phone company insists that, for safety reasons, I
should switch off my phone when I鈥檓 in a petrol filling station. What could
happen if I forgot to do so鈥攁nd how real is the danger? Have any accidents
actually been caused by mobile phones in filling stations?
Dermod Quirke
Halifax, West Yorkshire
Air space: We have tried the experiment taught by science teachers, in which
a candle standing in water is covered by an upturned glass. The candle goes out
and the water level rises in the glass. We are taught that the rising water
level is caused by oxygen being consumed by the burning candle. However, if we
have four candles burning under the glass instead of one, the water level rises
much more. Why?
Emma (aged 9), Rebecca (aged 12) and Andrew Fist (aged 11)
Norwood, Tasmania
Rig dwellers: I work on a North Sea oil platform and have often wondered what
our numerous gull inhabitants do during severe weather. They certainly cannot
sit it out on the water or glide above the storm and I assume they don鈥檛 fly
ashore. Just what do they do?
Charlie McGregor
The North Sea
It鈥檚 the Last Word鈥檚 fourth birthday. When the column began in March 1994 we
weren鈥檛 even sure it would fill a weekly page, but thanks to you, our readers,
the column just rolls along. We鈥檇 like to thank everyone who has ever written
in, by name, but the list would run to hundreds of pages. Instead, we鈥檙e
publishing a list of our star correspondents and the number of responses they
have had printed. If your name appears below, a thank-you is on its way to you.
And if you want to join this lucky band, pick up your pens and paper and start
writing.
Jon Richfield 18, M.V. Wareing 9, Michael Brimicombe 6, Ross Firestone 5,
Gavin Whittaker 5, C.R. Cavonius 4, Christopher Gardner-Thorpe 4.