What makes Black Bamboo black?

[foxd]

Sometime back someone posted where they had gotten P. nigra to turn black by covering a section of culm. I tried this and it had no effect. Just to add to the confusion on this, I was looking at this culm less than two weeks ago wondering how long it was going to take to turn black. This is what I see today.



I would swear that culm was mostly green two weeks ago! What happened?

[BooKing]

My nigra new culms turn black a few weeks after it has fully leafed out. It does it first with gradual spots which get bigger and start covering more area of the culms till it is fully black. The more sun the culms are exposed too, the more rapidily they change color at least that's what I have noticed with mine. There are alot of cultivars out there so there is alot of variation I suppose in additional to climatic conditions.

[foxd]

On mine I've noticed that the more shaded areas get darker faster. The first year in the ground the culms got dark over the summer. The second year they hardly turned color. And now they showed little color change until the past two weeks.

My suspicion is that it is weather related. Hmmm... It was rather cool and rainy recently. I know that the weather affects how fall colors turn out. I could see how it would account for the proliferation of P. nigras that change color at different rates. Not really different cultivars, but different climates effecting the same cultivar differently.

Perhaps this would make a good research project for someone.

[Roy]

I grew P. nigra for about 20 years and, with all culms growing basically growing in the same location, I would some some of the culms would turn black, some a chocolate color, and some green with speckled black and brown spots. My P. nigra would usually turn, what ever color it was going to be, within 6 months of its shooting time. Mine grew in mostly shade, with a few hours of direct sunlight in the middle of the Summer.

[CJW]

Why does black bamboo turn black.. well it is caused by melanin in the culms.

[Roy]

Why does black bamboo turn black.. well it is caused by melanin in the culms.

OK. What causes the melanin to make the green culm appear black to our eyes? The culm was green, now it's black. What was the catalyst that started the melanin into the action so that now we visually see black culms?

[philinshelton]

One of the posters on this forum has a fairly mature planting that has never colored up well...looks like 'Punctata' at its best. The grove is pretty much left to its own devices, so it's water and nutrient deficient. The owner informed me that the divisions he potted up and pampered turned jet black in a couple of weeks. Maybe he will post some comparative pics?

[BooKing]

That's an interesting point Phil. I baby the heck out of my bamboos and I am wondering if maybe that has an influence in how fast the color changes with the nigra.

[foxd]

From what I've observed on mine, the sections of the culms that get less light seem to darken faster than the ones that get more light. We also got cooler temperatures with a fair amount of rain during the time the culms darkened quickly. Given that the culms that get less light would be cooler, I'm tending to think that cool temperatures with lots of moisture have a major effect.

[CJW]

UVB radiation causes the melain to darken. UVB/Short wave UV causes the bamboo to "tan".

when I grew my nigra rhizomes in pots under metal halide lamps the nigra would never keep any green at all.
Metal halide has intense UVB output. / you can tan/sunburn your bamboo and retinas if not careful with these lights. DANGER!

Just because you experience a cloudy rainy day doesn't nessesarily mean your UVB rating drops to nil, UVB is much more penetrating than UVA and can penetrate clouds with not too much difficulty. Also your surroundings have materials that refract UVB in different ways.
The melanin in black bamboo takes time to develop outside/natually and gradually builds. Just because you have a cloudy couple of days doesn't mean it's not going to show it's colours to you, the photochemical reaction is still occuring within the culm cells.

[foxd]

CJW: I am wondering how you treat your P. nigra under the metal halide lamps. Fertilizer? Watering? Do you mist the leaves regularly? I'm curious about every detail.

[foxd]

Added bit of info: Copper is needed for the production of melanin. Tyrosine is a precursor and is oxidized in the process of producing melanin.

[foxd]

Another data point: An earlier discussion about the same question on Gardenweb.

http://forums.gardenweb.com/forums/load ... 13285.html

When I tried the experiment, covering sections of Black Bamboo to shield them from light caused no change in coloring from the uncovered sections.

I have a mental image of next year my covering the black bamboo with a wide array of things to try and pin down what exactly triggers the color change. I could be that color change in different cultivars trigger on different things.

[Markj]

This is an interesting subject and I'm not sure all the answers are out there, it's easy to try and explain Ph. nigra but whatabout the form boryana-why only patches of back. And then there's the stripes that appear on Ph. irridescens/violascens etc.

It's also a subject pretty much avoided by all the books here, none go into any detail with this subject. The colour changes that happen withing the cell structure giving yellow sulcus etc are pretty well known- but these colours are present from day one.

It's the changes that occur over time that need explaining, and it'll be nice to see a proper study done within controlled environments and backed up with facts.

[BooKing]

The only 'Fact' I know about bamboo is that it is highly addictive