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Name:   Susan
Status:    educator
Age:    50s
Location: N/A
Country: N/A
Date: Around 1999  


Question:
How are the leaves/needles of coniferous trees adapted to their environment (vs. broadleaf, deciduous trees)?


Replies:
Needles, with smaller surface and fewer pores, lose water much less rapidly than broad leaves, which helps them adapt to winter's drying. Lack of available water in winter is as much a factor in leaf function as is cold. Any decent botany book will explain further.

J. Elliott


Susan,

A general answer would be that conifer needles, in comparison to broadleaf leaves, are thicker, tend to have waxy coatings, and are more numerous. These qualities enable the tree to hold them for several seasons, in comparison to deciduous trees regular leaf loss. The waxy coatings promote water conservation and enable the trees again to hold a canopy during dry periods of the year when water might not be available. The small size and number of needles provides a mechanism by which a tree can effective capture a great percentage of incident sunlight. (This can be seen in the (general) lack of light under such general as spruce, fir, or hemlock.) This capability can reduce plant competition for nutrients with those species which are shade-intolerant.

It should be noted that evergreen trees do in fact lose a percentage of their needles during the year, but the investment of the entire canopy does not have to be replaced yearly, as occurs with deciduous trees. One noted exception, the larch, is a deciduous conifer; because of this, the species is a poor choice for a holiday tree.

Thanks for using NEWTON!

Ric Rupnik


Conifers go beyond deciduous angiosperms in showing adaptations to cold climates, with spire shapes to shed snow. Because of the slow nutrient release in the soil, it may be too expensive to replace leaves each year, so conifer leaves are evergreen.

Anthony R. Brach, Ph.D.



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