Wayne,
Your comment on mineral uptake by the mustard family reminded me
(correctly, I hope) that the the cruciferae are one family that does not use
mycorrhizae to mediate mineral uptake. Maybe the mycorrhizal associations
account for some of the variability in heavy-metal uptake in other families.
Martin
2011/4/16 Wayne Tyson <[email protected]>
> The original post may be related to the "eat the weeds" movement, one I
> have long considered a good idea while suffering no illusions that it will
> have any real impact upon the weed "problem."
>
> I eat weeds because I prefer them to most of their highly developed or
> CMO'd relatives. The weeds often, in addition to being more tasty, contain
> more nutrition than their cultivated cousins. Chenopodium album, for
> example, a common roadside weed, is one of my favorites. It is an
> "accumulator" (what plant isn't), containing a lot of iron (iron is a vital
> nutrient; it also is a poison--dosage is important). I do, however, pay
> attention to the substrate upon which they are growing. I prefer hillsides
> to stream bottoms unless I know the watershed is pretty free of
> contamination. Stream bottoms, especially those into which contaminants,
> often in the form of raw sewage drain, often contain the "best" crops of the
> lushest weeds. In my ignorance of the specifics, I rely upon the
> precautionary principle, "the solution to pollution is dilution," and a
> smidgen of knowledge (which we all know can often get one into more trouble
> than ignorance), and perhaps some myths I have unwittingly adsorbed (or
> worse, absorbed) along the way. I avoid roadsides and vacant lots of unknown
> history too. I trust my own ignorance more than that of agribusiness, but
> that's far from perfect.
>
> WT
>
>
> ----- Original Message ----- From: "malcolm McCallum" <
> [email protected]>
>
> To: <[email protected]>
> Sent: Saturday, April 16, 2011 7:10 AM
>
> Subject: Re: [ECOLOG-L] where do edible plants retain lead and other
> contaminants?
>
>
> Wayne brings up a good point.
>
> The bioavailability of toxic compounds, including metals is affected
> by many things among which pH can be one.
> In fact, the issue of TMDLs in the clean water act is based on problem
> that each stream has its own water chemistry and organic load. This
> causes us to require specific total maximum daily loads (TMDLs) of
> each compound for each stream (or portions thereof). TMDLs were
> supposed to be completed for surface waters in most states a long time
> ago, unfortunately the process is not done everywhere!
>
> Malcolm
>
> On Fri, Apr 15, 2011 at 9:03 PM, Wayne Tyson <[email protected]> wrote:
>
>> Ecolog:
>>
>> This rings a vague bell for me too. There was some work done in the
>> British
>> Isles (Scotland) on very crisp ecotones across pH differences using one
>> grass species. Also, I seem to recall that the Dutch were using willows
>> that
>> were supposed to be hyperaccumulators and they were burning them for fuel,
>> then disposing of (or "mining") the heavy-metal "laden" ash. There is, of
>> course, considerable literature on "phytoprospecting." I, too, would like
>> to
>> be brought up to date in this area, and educated on the particulars. For
>> example, I would like to know just how accumulation or "rejection"
>> functions, and what processes are involved. For example, how does pH
>> affect
>> the rate and amount of absorption? What other chemical and physiological
>> processes are involved? Why are some heavy metals (chromium, selenium,
>> arsenic, etc.) apparently readily absorbed (by the Chenopodiaceae, for
>> example--and the mustard family), and lead apparently not? Is it as simple
>> as semipermeable membranes, whether or not they are soluble and under what
>> conditions? Is something going on in the rhizosphere that evades some
>> analytical procedures?
>>
>> WT
>>
>>
>> ----- Original Message ----- From: "Martin Meiss" <[email protected]>
>> To: <[email protected]>
>> Sent: Friday, April 15, 2011 9:04 AM
>> Subject: Re: [ECOLOG-L] where do edible plants retain lead and other
>> contaminants?
>>
>>
>> A long time ago, when I was learning about plant ecotypes, I heard of
>> research on the adaptation of plants to high lead levels found in piles of
>> mine tailings. If I remember correctly, local races of plants were forming
>> that were able to adapt to toxic soils. This raises these questions: if
>> plants ARE NOT taking up the heavy metals, what is the mode of toxicity?
>> (Are ions in the soil blocking the uptake of needed substances?) What is
>> the mechanism of resistance that was evolving? If it involved the blocking
>> of uptake of lead and other metals, that implies that other, non-adapted
>> plants DO take them up.
>> Can any one comment on this aspect of the issue?
>>
>> Martin M. Meiss
>>
>> 2011/4/15 Judy Che-Castaldo <[email protected]>
>>
>> Hi Ben,
>>> In general you are unlikely to find lead in the shoots of plants, because
>>> it
>>> is not very soluble and most plants exclude heavy metals. The edible
>>> plants
>>> that may have Pb would likely be leafy vegetables (grown close to the
>>> ground) and root vegetables (as mentioned earlier) because of the
>>> associated
>>> soil particles containing Pb.
>>>
>>> There are some plants that uptake heavy metals into their shoots but few
>>> for
>>> Pb, and even those may only do so under rare circumstances (such as
>>> phosphorous deficiency - Chaney 2007 J. Environ. Qual. 36:1429–1443).. If
>>> you are interested in other contaminants you can look into the metal
>>> hyperaccumulation literature. Many of these plants are in the mustard
>>> family but probably are not normally eaten.
>>>
>>> best,
>>> Judy
>>>
>>>
>>> Judy Che-Castaldo
>>> BEES program, Biology Dept.
>>> University of Maryland
>>> (301)351-8290
>>> http://www.life.umd.edu/grad/BEES/students/che.html
>>>
>>>
>>
>> -----
>> No virus found in this message.
>> Checked by AVG - www.avg.com
>> Version: 10.0.1204 / Virus Database: 1435/3511 - Release Date: 03/16/11
>> Internal Virus Database is out of date.
>>
>>
>
>
> --
> Malcolm L. McCallum
> Managing Editor,
> Herpetological Conservation and Biology
> "Peer pressure is designed to contain anyone with a sense of drive" -
> Allan Nation
>
> 1880's: "There's lots of good fish in the sea" W.S. Gilbert
> 1990's: Many fish stocks depleted due to overfishing, habitat loss,
> and pollution.
> 2000: Marine reserves, ecosystem restoration, and pollution reduction
> MAY help restore populations.
> 2022: Soylent Green is People!
>
> Confidentiality Notice: This e-mail message, including any
> attachments, is for the sole use of the intended recipient(s) and may
> contain confidential and privileged information. Any unauthorized
> review, use, disclosure or distribution is prohibited. If you are not
> the intended recipient, please contact the sender by reply e-mail and
> destroy all copies of the original message.
>
>
> -----
> No virus found in this message.
> Checked by AVG - www.avg.com
> Version: 10.0.1204 / Virus Database: 1435/3511 - Release Date: 03/16/11
> Internal Virus Database is out of date.
>
