Bulbs and Corms and Tubers

ben kisuisje bmouroux@hotmail.com
Mon, 14 Dec 2009 23:30:51 PST
Hello bulb-friends,
I did a little article on a French list with details from site SFIB (specializing in Iridaceae) ... Ienclose the link in French and a translation with google. 
"The term bulb is generally used to describe a remarkable body of reserve, usually underground, a perennial herbaceous vegetation often seasonal. This generic term is in fact different structures: leaves (true bulbs), stems (corms, rhizomes, tubers, pseudobulb) or tuberous roots. 
Bulb (Bulb sheet): Body reserves the structure with a large bud consists of thickened modified leaves (scales), loaded with nutrients, emerging on a condensed rod (plate). These scales are the basis of developed leaves (eg Amaryllidaceae, Alliaceae, Hyacinthacées) or without leaves are green leaf (Tulipes. ..). 
We can distinguish bulbs coat and scaly bulbs. Bulb tunics, ie covered with a protective coating dries, usually compound leaves entirely sheathing, such as onions cooking (Amaryllidaceae, Alliaceae, Hyacinthacées, Tulip ...). 
The scaly bulbs are composed of fleshy scales not sheathing, loosely interwoven and not wrapped in a tunic (Lily, Fritillaria). 
The bulb remains and rebuilds its reserves during the growth cycle (Amaryllidaceae) or leave room for a replacement bulb size to flower (tulip, Ixiolirion) or bulblets (Cardiocrinum).
Corm (bulb solid): Appearance neighbor bulbs but the reserves are accumulated in the fleshy stem. In many Iridaceae (Crocus, Gladiolus, Freesia ...) flower buds are present at the summit and the whole is surrounded by a coat. The corm exhausts its reserves during each cycle and is replaced by a new one. Erythronium and Colchicum corms form of an entirely different type.

Rhizome: rod to horizontal development, underground or creeping stems emitting air and bearing adventitious roots. More or less thickened it serves as the reserve and survival. Lengthening by the end so that it conquers every year a new soil (while the older parts die) and it is also spread vegetatively.
Examples: Iris Garden, Canna, Anemone, Lily ...

Tuber: thickened underground stem transformed into a body of reserve on top of the vegetative buds.
Examples: tuberous begonias, cyclamen, Siningia .
Pseudobulb: thickening of the fleshy base of a stem with the false appearance of a bulb. Occurs among orchids (storage organ) and at plants myrmecophilous (passenger ants).

Tuberous roots: Roots fleshy converted into body reserves (the absorption function is ensured by other roots of normal appearance). Vegetative buds are present at the collar at the base of the old air shaft.
Examples: Dahlia Eremurus, Buttercup ...

Geophytes: Plants whose buds destined to survive spend the winter buried in the ground. Most bulbous plants geophytes are but some are epiphytes (several Hippeastrum, Pamianthe, Cyrtanthus epiphyticus ...) The terms and bulbous geophytes are not synonymous.
The bulbs have annual growth cycles varied:
Many plants have a seasonal summer [Summer grower] (eg gladiolus, Siningia, Hippeastrum vittatum).
Others, from arid regions has been or mild winter, have a growing winter [Winter grower] (eg, Lachenalia, Nerine sarniensis - South Africa; Rhodophiala bifida - Argentina; Lycoris radiata - Asia ...).
Others, without rest period also marked, keep foliage Permanent [Evergreen] (eg Zantedechia aethiopica, Cyrtanthus elatus, Hippeastrum papilio, Haemanthus albiflos, Eucharis ...)." 		 	   		  
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