Kiwifruit is not covered in hairs. It’s covered in trichomes. And only if you’re talking about green Actinidia chinensis var. deliciosa. But, why? One answer is: pretty much to keep it from drying out. Another is: because it’s a polyploid from western China and was kind of chosen at random to be the most commonly grown kiwifruit, and they’re not all fuzzy. Those aren’t mutually exclusive answers. Put on your ecophysiology hats and grab a paring knife.
Think of fruit growth as a balancing act between ingoing and outgoing fluxes. When the balance is positive, fruits grow. When it is negative, they shrink—or shrivel. The main fluxes in question are carbon and water, which enter the fruit from the xylem and phloem of the plant vascular system. Water is lost mainly to the atmosphere via transpiration (evaporative water lost through stomata and other pores and from the skin surface). Keeping the ledger positive isn’t an easy job for a fruit. Hot, dry, and windy weather encourages transpiration and thereby increases the odds that a fruit will experience water stress. Excessive sunlight may cause sunburn. Fruits also need to avoid attack from pathogens and herbivores before the seeds within mature. A fruit’s skin—its cuticle and epidermis—is its first line of defense against abiotic and biotic threats. Some fruits resort to creative coverings to get the job done.
Here I’ll take a close look at the skin of kiwifruits. Why, exactly, are they so fuzzy?
A heart-shaped green kiwifruit (Actinidia chinensis var. deliciosa), covered in fuzzy trichomes
This is our second of our two contributions to Advent Botany 2015. All the essays are great!
An early image of candy canes. From Wikipedia
The candy cane, that red- and white-striped hard candy imbued with peppermint oil, is a signature confection of the winter holidays. Peppermint has a long history of cultivation and both medicinal and culinary use. Infusions of the plant or its extract have been used for so many hundreds of years throughout Europe, North Africa and Western Asia that the early history of peppermint candies, including cane-shaped ones, is murky. Fortunately, the biology behind peppermint’s famous aroma is better known than the story of how it came to be a Christmas staple. Continue reading
Posted in Flavor, herbs, Uncategorized
Tagged aroma, candy cane, essential oil, flavor, fragrance, hybrid, Jeanne L. D. Osnas, Lamiaceae, Mentha, menthol, peppermint, receptor, spearmint, trichome, watermint
A batch of lemon balm-lemon verbena syrup reminds Jeanne of the multiple evolutionary origins of lemon flavor.
The citrus lemon itself is only one of many plant species that lends its namesake flavor or fragrance to our food and drinks. Lemon flavor primarily comes from a few terpenoid essential oils: citral (also called geranial, neral, or lemonal), linalool, limonene, geraniol, and citronellal. The production of one or more of these essential oils has independently evolved multiple times in species on widely separated branches of the plant phylogeny (see figure).
Phylogeny of plant taxonomic orders with edibles (click the tree to enlarge). Orders with species with lemony essential oils are highlighted in red. For a refresher on reading this phylogeny, please see our food plant tree of life page.
Posted in Flavor, herbs, Recipes
Tagged citronella, Citrus, essential oil, evolution, flavor, Jeanne L. D. Osnas, Lamiaceae, lemon, lemon balm, lemon verbena, lemongrass, syrup, terpenoid, trichome, Verbenaceae