Color of leaves

[brookledge]

As I drive around I see some maple bushes that tend to be grouped by colors some predominately yellow other orange etc. I know that trees under stress will turn orange sooner than healthy ones, but other than different chemical componants of the soil is there any reason why trees tend to be one color or another?
Keith

[TF Maple]

I think the color is genetic if I'm not mistaken. Over in Asia they only have yellow leaves, no orange or red. The color is there all year and is just covered up by the green chlorophyl. As the leaves die and loose the green, we see the color that was there all along.

[DrTimPerkins]

As I drive around I see some maple bushes that tend to be grouped by colors some predominately yellow other orange etc. I know that trees under stress will turn orange sooner than healthy ones, but other than different chemical componants of the soil is there any reason why trees tend to be one color or another?
Keith

Very brief answer....given that there are chapters and entire books on this subject...and at least two more on the way in the next year.

Differences in foliage color expression come from differences in tree species: oaks tend to be bronze/brown, poplar are yellow/brown, birches are yellow, red maples tend to be red, sugar maple are red/orange/yellow, etc. Variation in this is due to the season, fungus, soil chemistry (especially nitrogen), water availability, stress, etc. List goes on and on.

Green is from chlorophyll, the primary pigment in photosynthetic light harvesting. When it breaks down due to cold weather/high light (fall conditoins), the yellow/browns that were always there but were masked by the chlorophyll. The yellow/brown colors are due to carotenoid pigments, which are actually ancillary/helper pigments for the capture of light energy in photosynthesis. The red color (anthocyanin) is a compound that is actually actively formed in both the spring and fall (as opposed to having been there all along). The purpose of this red pigment is not totally understood, and seems to vary in different types of plants. It is likely they have some important role, as it requires the plant to invest energy to actually make these compounds. A number of possible functions have been postulated (photoprotection from cold weather/high light, antifreeze compounds, anti-stress/antioxidative compounds, anti-herbivory of insects). In maples at least, it doesn't appear that they are functioning as significant photoprotective light screens (protecting the light harvesting apparatus during cold/high light conditions) as has been suggested, and they also don't seem to be particularly effective as antioxidative compounds either (this was the subject of Dr. Abby van den Berg's Doctoral Dissertation). So the reason they are there is far from clear. This topic is the subject of ongoing investigation by Dr. Abby van den Berg (UVM PMRC), Dr. Tom Vogelmann (UVM Plant Biology), and I. The specific details are probably not of huge interest to very many maple producers. Two scientific review papers are in preparation by Dr. Abby describing the state of the science.

[red maples]

I have noticed alot more brown than usual. Is that due to lack of rain this year?

[DrTimPerkins]

I think the color is genetic

It varies by genus and species...so that is genetic.


The color is there all year and is just covered up by the green chlorophyl. As the leaves die and loose the green, we see the color that was there all along.

That is correct as far as the yellow pigment is concerned. The red/orange colors are actually actively synthesized by the plants about the time that you see them. They were not there all along.

[C.Wilcox]

Variation in this is due to the season, fungus, soil chemistry (especially nitrogen), water availability, stress, etc. List goes on and on.

Dr. Perkins- does nitrogen actually play a significant enough role by itself to be able to affect leaf color? In other words, if someone fertilized their sugarbush would the trees possibly show a difference in color that fall?

[DrTimPerkins]

Dr. Perkins- does nitrogen actually play a significant enough role by itself to be able to affect leaf color? In other words, if someone fertilized their sugarbush would the trees possibly show a difference in color that fall?

Yes, nitrogen alone can play a significant role in color expression, however generally it works the other way around. Trees that are deficient in nitrogen tend to turn sooner and more brilliantly. That's why maple trees growing in wet areas are often quite red (well that and the fact that they are frequently soft maples). Nitrogen is typically low in wetter areas.

[brookledge]

I knew that other species have certain colors but wondered why maples turn 3 different colors and you answered my question.
Keith

[Revi]

There are some spectacular colors happening around here this week.

I just started to notice them this weekend.

The show has just started, but it's going to be good.