Why does Sumac have hairy twigs?

redalienx11 · December 21, 2005, 11:15:35 AM

...For that matter, why do any plants have hair. Is there an evolutionary purpose?

etat · December 21, 2005, 11:33:45 AM

Swamp donkey is the expert around here in such matters but this is what i found.

The technical term for plant hair is trichomes. Unlike animal hair trichomes are often living cells. In different plants trichomes can run the gamut in structure, appearance, and texture. Some trichomes are frail, some coarse; some are branched like tree limbs, others star-shaped; some are long and straight, others are short and curly. Just as mammal hair serves various protective purposes, including insulation and camouflage, so do trichomes. Trichomes can be insulating by keeping frost away from leaf cells. They can help reduce evaporation by protecting the plant from wind and heat. In many cases, trichomes protect plants from herbivorous insects that may want to feed on them. And in some cases, if the trichomes are especially stiff or irritating, they may protect a plant from larger herbivores.

I also found this. Unbranched hairs are typical of some species while others have branched hairs. The multicellular hairs of the Common Ivy are described as stellate. Hair type can be used to distinguish between closely related species.

and this........Trichomes are minute highly specialized outgrowths that are found along any surface of a plant and are designed to enhance a plant's chances of survival. These accessory structures occur most often along stems and leaves but can also be found on the surface of petals and also comprise the fragrant and sweet necturaries that draw pollinating creatures. Many forms of trichome help adjust the microclimate on the surfaces of the leaves by reflecting solar radiation and prevent evaporation of critical water supplies. Trichomes that manifest curly shapes are developed for use as reflectors by such plants as the desert brittlebush. Each variety of plant produces trichomes that are most suited to cope with the conditions of its environment. Although various forms exist, these appendages commonly occur as glandular, nonglandular, scales, papillae, or hair-like structures.

Glandular trichomes contain volatile oils as well as other secretions that can cover the surrounding surface of the leaves and petals. Aromatic plants (such as lavender) as well as culinary herbs (mint, sage, thyme) store essential oils in globe-shaped head cells. Some trichomes have specifically evolved to act as defense mechanisms. Trichome structures that occur in large numbers may protect a plant by making its tissue less edible or hospitable to feeding and breeding insects. Several plant varieties form glandular structures that produce chemicals that are poisonous to insects that contact, ingest, or even inhale trichome secretions. The catchfly plant produces a sticky substance that adheres to and traps unsuspecting insects. Strategically located to minimize nibbling from pests, trichome structures typically lie in greater numbers along the edges of leaves. When trichomes grow in abundance, they cause leaves to have a fuzzy appearance.

Tom · December 21, 2005, 11:40:14 AM

Welcome aboard, redalienx11.

We think of these things backward sometimes. I don't think that evolution creates solutions to problems as much as it allows those with the solutions to live and those without soon pass into oblivion.

It's just a guess but I'd say that the hair, in most instances and especially on leaves, prevents the stoma(breathing holes) from becoming stopped up from solid particles like smoke, dust, etc. Those plants that had no hair and were susceptible to plugged stomata, died out. Perhaps some plants are not as susceptible and the hairs serve no purpose or were never there to begin with.

Perhaps it is a device that provided more surface area for the absorbtion of gases and nutrients too. Root hairs perform that function so, perhaps, hairs on the rest of the plant do also.

populus · December 21, 2005, 12:10:23 PM

Tom - that is one of the best one-sentence descriptions of adaptation I've seen!

Like most adaptations, plant hairs certainly do multiple things, including all those that cktate and Tom mention. It is usually not possible to separate out these multiple roles. Think of the multiple roles played by our own hair.

It is interesting that we have two very closely related species, staghorn sumac Rhush typhina with hairs and smooth sumac, R. glabra without hairs. Staghorn sumac is the more northerly species, suggesting that winter protection from desiccation or from sun scald are possible roles.