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The Daily Telegraph - Gardening - - New Books -

Is the air in­side a bell pep­per the same as the air out­side? This ques­tion is a peren­nial favourite, and a num­ber of ex­per­i­ments have been con­ducted to get at the truth. The smooth, ap­par­ently pore­less outer skin of a bell pep­per, Cap­sicum an­nuum, leads to the sup­po­si­tion that the pep­per can­not “breathe” and, there­fore, that the air in­side must have its own at­mos­phere.

De­spite the shiny ex­te­rior, there is prob­a­bly some lim­ited dif­fu­sion between the in­side and out­side of the pep­per – or the in­te­rior at­mos­phere would have an even higher level of car­bon diox­ide. One ex­per­i­ment into seed devel­op­ment in pep­pers ar­ti­fi­cially re­duced the amount of oxy­gen in­side the fruit – and this was found to af­fect the seeds ad­versely.

The con­clu­sion was that the pep­pers have enough con­trol over their in­ner mi­cro­cli­mate to al­low suc­cess­ful seed devel­op­ment.

As ever, an­swer­ing one ques­tion raises oth­ers: does the air in pep­pers vary at day and night times? Does the air change as a pep­per grows? And so on. Use­ful or not, in­ter­net spec­u­la­tion can con­tinue for a while yet. Tests con­clude that the air out­side and the pep­per’s in­ter­nal air are dif­fer­ent. Reg­u­lar air con­tains roughly 78 per cent ni­tro­gen and 21 per cent oxy­gen; “pep­per” air has up to three per cent less oxy­gen and up to three per cent more car­bon diox­ide.

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