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Index of Subjects
in Spring. Such an impo
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Hi Dave, lemnaphiles,
I think the point was that if the primary experimental test of winter sinki=
ng of this little plant is just that, actually sinking, then this wasn=92t =
yet observed in your test in the =91control' case, the light-exposed cultur=
e (as you point out, I had control and experimental conditions reversed). =
If sinking didn=92t yet happen in the brightly lit control, you can hardly =
argue about what was happening in the experimental (dark) culture, as the b=
asic alleged phenomenon (sinking) has not yet been reproduced even in the c=
ontrol. =91Alleged?=92 -- do they actually sink anyway, and if so, in whic=
h species?
I spent a few minutes looking for duckweed info on-line including at Wikipe=
dia, of which www.mobot.org/jwcross/duckweed/duckweed.htm<http://www.mobot.=
org/jwcross/duckweed/duckweed.htm>
is quite informative. This doesn=92t reveal anything about the actual pla=
nts sinking in winter, and this link indicates that what do sink in some sp=
ecies are =91turions=92, seeds and fronds, not the basic leaves themselves:=
the latter presumably disintegrate and die at our latitudes, when a pond f=
reezes. Both turions (vegetatively reproduced) and seeds contain dense sta=
rch but lack aerenchyma air pockets, and sink to remain dormant through the=
winter, though only one Lemna species makes turions. Lot of research into=
mass-culturing some species for possible efficient commercial food product=
ion, while effectively removing much CO2 from the atmosphere.
My query about possible buoyancy produced by oils (density 0.8-0.9 g/cc) wa=
s a probable non-starter, insignificant. Lipid composition of other semi-a=
quatic plants like watercress and Chinese watercress is only 0.1-0.2%. Buoy=
ancy apparently is achieved there through hollow air-filled stems.
Steve
----------------------------------------------
On Sep 29, 2018, at 11:38 AM, David <dwebster@glinx.com<mailto:dwebster@gli=
nx.com>> wrote:
Hi Steve & All,
Yes we can agree with the fact that they sink in the fall and rise in t=
he spring and, by analogy with plant processes in general one may assume th=
at these changes in position are under hormonal control. The long rambling =
discussion last year was largely an attempt to consider possible mechanisms=
. One may take it as given that photosynthesis requires light and respirati=
on continues under all conditions but slows as temperature decreases. Also =
given; CO2 is more soluble in water than O2.
Note that my control was the dish on the windowsill and treated was the=
dish in darkness.
The original article proposed starch accumulation in the fall as the me=
chanism of sinking and loss in the spring as the mechanism of rise. Someone=
last year proposed an alternative;
The alternative being-- With shortening days in the fall and consequen=
tly less photosynthesis, the cellular release of CO2 would exceed the relea=
se of O2. And as photosynthesis approached zero, CO2 would predominate in t=
he gas filled spaces. This reversal in gas composition ( O2 > CO2) would re=
nder gas filled spaces, which were not isolated from the medium, more subje=
ct to flooding due to the greater solubility of CO2.
If the above reasoning had been valid then my treated plants, kept in d=
arkness for nearly a week, would have all sunk. They showed no greater tend=
ency to sink than the control. Consequently flooding of intercellular space=
s (or specialized aerenchyma) by water is not the mechanism by which averag=
e density of Lemna increases in the fall.
So I conclude that accumulation of starch (density 1.5) in the fall, as=
growth slows to zero and respiration slows as temperature lowers, is the m=
echanism of sinking. And conversely greater respiration, due to rising temp=
erature and resumption of growth leads to loss of starch, a decrease in ave=
rage density and rise to the surface.
The original article noted that Lemna is more efficient than corn as a =
producer of starch; impressive. I suspect the starch content in the fall wo=
uld be higher than in the spring and this I think is true of most plans in =
temperate climates.
Yt, DW Kentville
------ Original Message ------
From: "Stephen Shaw" <srshaw@Dal.Ca<mailto:srshaw@Dal.Ca>>
To: "naturens@chebucto.ns.ca<mailto:naturens@chebucto.ns.ca>" <naturens@che=
bucto.ns.ca<mailto:naturens@chebucto.ns.ca>>
Sent: 9/28/2018 11:57:50 PM
Subject: Re: [NatureNS] Duckweed
Hi Dave,
I=92d forgotten about this, but isn=92t the primary observation to explain =
that the plants routinely sink in the winter and rise again in the spring? =
What the mechanism is, is an interesting but secondary consideration. In=
your =91experimental=92 case with lighted duckweed, it should be producing=
and accumulating some sort of gas mixture by September's photosynthesis, m=
aybe plus some concurrent respiration. Your =91control', dark duckweed, sh=
ould have no photosythesic activity, so only respiration should produce any=
gas at all, presumably CO2.
The problem is that neither =91expt' nor =91control' actually sank on Sept =
27. Since the plant material including any dense starch should anyway have=
an average density >1g/cc (i.e. greater than plain water*), excluding any =
gas spaces, both cases must still be floating according to some undissolved=
gas inclusions, though not necessarily the same mix of CO2/O2 in the two c=
ases. You get an A+ for industry and design, but Lemna gets an F for coope=
ration.
*Something I=92d not considered that you may know about but I don=92t is oi=
l/fat production in plants, which obviously is important for some land plan=
ts (canola, sesame, olives etc). Oils have specific gravities <1, around 0=
.9 g/cc, so enough oil volume could be sufficient to float a water plant wi=
thout invoking gas spaces. If something dense like starch gets converted t=
o an oil in spring, could that contribute, or is this just fantasy?
Is it possible that the trigger for sinking, whatever its mechanism, is a p=
articular drop in day length that had not yet been closely approached by Se=
pt 27, and especially in your toasty living room (temperature might be anot=
her factor)? If you haven=92t flushed them in frustration, you should con=
vey both your test subjects to an unheated outhouse and extend your experim=
ent there at least to freeze-up.
Steve
---------------------------------------------------------
On Sep 27, 2018, at 12:35 PM, David <dwebster@glinx.com<mailto:dwebster@gli=
nx.com>> wrote:
Dear All,
I have had my eye open this summer for some Lemna to test the gas compo=
sition idea; the more soluble CO2 predominating as days shorten leading to =
flooding of gas spaces and sinking; photosynthesis predominating in spring =
as days lengthen leading to flooded air spaces being filled by less soluble=
O2 and rise to the surface.
And I was able to collect some on Sept 21 without having to wade in muc=
k of uncertain depth. So I set up a simple trial; some kept in darkness, ex=
cept for a few minutes daily for observation, and some kept on a windowsill=
.
By Sept 27 those kept in darkness showed no tendency to sink but were n=
oticeably less green than those exposed to daylight and some artificial lig=
ht in the evening. This leads to the conclusion that flooding of intercellu=
lar gas spaces when CO2 predominates does not cause sinking of Lemna. The =
converse explanation that Lemna rises to the surface in the spring when int=
ercellular spaces become filled by less soluble O2 is accordingly voided.
The explanation given in the link posted by Nancy on Oct 3, 2017 is con=
sequently more sound. Starch accumulation in the fall. as photosynthesis ex=
ceeds respiration at lowering temperature, leads to sinking. Starch consump=
tion, as temperature warm in the spring and new buds start to grow, leads t=
o rise to the water surface. [density of starch is high; 1.5 g/cm^3]
Yt, DW, Kentville
------ Original Message ------
From: "Stephen Shaw" <srshaw@Dal.Ca<mailto:srshaw@Dal.Ca>>
To: "naturens@chebucto.ns.ca<mailto:naturens@chebucto.ns.ca>" <naturens@che=
bucto.ns.ca<mailto:naturens@chebucto.ns.ca>>
Sent: 3/10/2018 3:20:47 PM
Subject: Re: [NatureNS] Duckweed
Interesting puzzle, perhaps not so simple. Any cell system like a live lea=
f is bound to be somewhat denser than pond water, regardless of denser star=
ch, so will naturally sink at all times unless kept buoyant by the extracel=
lular gas bubbles or some other modification. What seems to need explainin=
g is why the bubbles are maintained in summer (dissolved gases can pass thr=
ough lipid cell membranes quickly, so you=92d expect them to dissolve out i=
nto the surrounding pond), and why they disappear in winter. He doesn=92t =
seem to know if it=92s CO2 or O2 in the bubbles, or both. Perhaps they are=
largely O2 in summer and dissolve and normally pass out of the leaf to oxy=
genate the pond and dissolved CO2 moves in, but leaf photosynthesis is suff=
iciently high in summer to maintain them, despite these losses. In winter =
gas production simply stops, and the non-buoyant plants sink. As winter en=
ds, respiration produces bubbles with a different gas, CO2, and they rise a=
gain then switch over to O2 as photosynthesis picks up.
It therefore seems likely that these leaves have some special surface coati=
ng that slows down gas exchange with the pond. Maybe they still retain sto=
mata under the leaf which normally facilitate gas exchange for leaves in ai=
r, but these are modified to block or regulate gas exchange in water? Mayb=
e this is already known, just not to us here?
Steve
On Mar 10, 2018, at 10:45 AM, David <dwebster@glinx.com<mailto:dwebster@gli=
nx.com>> wrote:
Hi Nancy & All,
I admit not having wondered about this but I think he makes a simple pr=
ocess complicated. The air pockets to which he refers are presumably interc=
ellular spaces which in the absence of photosynthesis presumably can become=
water filled. Starch has a specific gravity of 1.5 g/mL and, in cooler wea=
ther starch will accumulate when respiration slows more than photosynthesis=
and the submarine will sink. With warming, growth resumes, respiration and=
starch consumption rates increase and the submarine rises.
Yt, DW, Kentville
------ Original Message ------
From: "nancy dowd" <nancypdowd@gmail.com<mailto:nancypdowd@gmail.com>>
To: naturens@chebucto.ns.ca<mailto:naturens@chebucto.ns.ca>
Sent: 3/10/2018 9:08:02 AM
Subject: [NatureNS] Duckweed
This is an interesting article on Duckweed seasonal disappearance and reapp=
earance in the Spring 2018 issue of Northern Woodlands Magazine.https://nor=
thernwoodlands.org/outside_story/article/duckweed-migration
I had never really thought about where it went in Fall or how it re-emerges=
in Spring. Such an important floating pond plant in productive fresh water
Nancy D
Sent from my iPad
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<html>
<head>
<meta http-equiv=3D"Content-Type" content=3D"text/html; charset=3DWindows-1=
252">
</head>
<body style=3D"word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-lin=
e-break: after-white-space;">
Hi Dave, lemnaphiles,
<div>I think the point was that if the primary experimental test of winter =
sinking of this little plant is just that, actually sinking, then this wasn=
=92t yet observed in your test in the =91control' case<font size=3D"3">, th=
e light-exposed culture (a</font><span style=3D"font-size: 12pt;">s
you point out, I had control and experimental conditions reversed). <=
/span><font style=3D"font-size: 12pt;"> If sinking didn=92t yet happen=
in the brightly lit control, you can</font><span style=3D"font-size: 12pt;=
"> hardly</span><font style=3D"font-size: 12pt;"> argue
about what was happening in the experimental (dark) culture, as the basic =
alleged phenomenon (sinking) has not yet been reproduced even in the contro=
l. =91Alleged?=92 -- do they actually sink anyway, and if so, in whic=
h species?</font></div>
<div><font size=3D"3"><br>
</font></div>
<div><font size=3D"3">I spent a few minutes looking for duckweed info on-li=
ne including at Wikipedia, of which
<a href=3D"http://www.mobot.org/jwcross/duckweed/duckweed.htm">www.mobot.or=
g/jwcross/duckweed/duckweed.htm</a></font></div>
<div><font size=3D"3">is quite informative. This doesn=92t reveal an=
ything about the actual plants sinking in winter, and this link indicates t=
hat what do sink in some species are =91turions=92, seeds and fronds, =
not the basic leaves themselves: the latter presumably
disintegrate and die at our latitudes, when a pond freezes. Both&nbs=
p;</font><span style=3D"font-size: medium;">turions (vegetatively reproduce=
d) and seeds </span><span style=3D"font-size: medium;">contain dense s=
tarch but </span><font size=3D"3">lack aerenchyma air
pockets, and sink to remain dormant through the winter, though only one Le=
mna species makes turions. Lot of research into mass-culturing some s=
pecies for possible efficient commercial food production, while effectively=
removing much CO2 from the atmosphere.</font></div>
<div><font size=3D"3"><br>
</font></div>
<div><font size=3D"3">My query about possible buoyancy produced by oils (de=
nsity 0.8-0.9 g/cc) was a probable non-starter, insignificant. Lipid =
composition of other semi-aquatic plants like watercress and Chinese waterc=
ress is only 0.1-0.2%. Buoyancy apparently
is achieved there through hollow air-filled stems.</font></div>
<div><font size=3D"3">Steve </font></div>
<div>----------------------------------------------<br>
<div>
<div>On Sep 29, 2018, at 11:38 AM, David <<a href=3D"mailto:dwebster@gli=
nx.com">dwebster@glinx.com</a>> wrote:</div>
<br class=3D"Apple-interchange-newline">
<blockquote type=3D"cite"><style id=3D"css_styles" type=3D"text/css"><!--bl=
ockquote.cite { margin-left: 5px; margin-right: 0px; padding-left: 10px; pa=
dding-right:0px; border-left: 1px solid #cccccc }
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padding-right:0px; border-left: 1px solid #cccccc; margin-top: 3px; padding=
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a img { border: 0px; }
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body { font-family: Segoe UI; font-size: 12pt; }--></style>
<div>
<div>Hi Steve & All,</div>
<div> Yes we can agree with the fact that they sink in the fal=
l and rise in the spring and, by analogy with plant processes in general on=
e may assume that these changes in position are under hormonal control. The=
long rambling discussion last year was largely
an attempt to consider possible mechanisms. One may take it as given that =
photosynthesis requires light and respiration continues under all condition=
s but slows as temperature decreases. Also given; CO2 is more soluble in wa=
ter than O2.</div>
<div> Note that my control was the dish on the windowsill and =
treated was the dish in darkness.</div>
<div> The original article proposed starch accumulation in the=
fall as the mechanism of sinking and loss in the spring as the mechanism o=
f rise. Someone last year proposed an alternative;</div>
<div> The alternative being-- With shortening days in th=
e fall and consequently less photosynthesis, the cellular release of CO2 wo=
uld exceed the release of O2. And as photosynthesis approached zero, CO2 wo=
uld predominate in the gas filled spaces. This
reversal in gas composition ( O2 > CO2) would render gas filled spaces,=
which were not isolated from the medium, more subject to flooding due to t=
he greater solubility of CO2.</div>
<div> If the above reasoning had been valid then my treated pl=
ants, kept in darkness for nearly a week, would have all sunk. They showed =
no greater tendency to sink than the control. Consequently flooding of inte=
rcellular spaces (or specialized aerenchyma)
by water is not the mechanism by which average density of Lemna increases =
in the fall.</div>
<div> So I conclude that accumulation of starch (density 1.5) =
in the fall, as growth slows to zero and respiration slows as temperature l=
owers, is the mechanism of sinking. And conversely greater respiration, due=
to rising temperature and resumption of growth
leads to loss of starch, a decrease in average density and rise to the sur=
face.</div>
<div> The original article noted that Lemna is more efficient =
than corn as a producer of starch; impressive. I suspect the starch content=
in the fall would be higher than in the spring and this I think is true of=
most plans in temperate climates. </div>
<div>Yt, DW Kentville </div>
<div><br>
</div>
<div>------ Original Message ------</div>
<div>From: "Stephen Shaw" <<a href=3D"mailto:srshaw@Dal.Ca">sr=
shaw@Dal.Ca</a>></div>
<div>To: "<a href=3D"mailto:naturens@chebucto.ns.ca">naturens@chebucto=
.ns.ca</a>" <<a href=3D"mailto:naturens@chebucto.ns.ca">naturens@ch=
ebucto.ns.ca</a>></div>
<div>Sent: 9/28/2018 11:57:50 PM</div>
<div>Subject: Re: [NatureNS] Duckweed</div>
<div><br>
</div>
<div id=3D"xc5dd5f1fc8d549c" style=3D"word-wrap: break-word; -webkit-nbsp-m=
ode: space; -webkit-line-break: after-white-space;">
<blockquote cite=3D"x-msg://8/29C78FB6-68C5-425F-9729-ABA4EEDC204D@dal.ca" =
type=3D"cite" class=3D"cite2">
Hi Dave,
<div>I=92d forgotten about this, but isn=92t the primary observation to exp=
lain that the plants routinely sink in the winter and rise again in the spr=
ing? What the mechanism is, is an interesting but secondary considera=
tion. In your =91experimental=92 case with
lighted duckweed, it should be producing and accumulating some sort of gas=
mixture by September's photosynthesis, maybe plus some concurrent respirat=
ion. Your =91control', dark duckweed, should have no photosythesic ac=
tivity, so only respiration should produce
any gas at all, presumably CO2.</div>
<div> </div>
<div>The problem is that neither =91expt' nor =91control' actually sank on =
Sept 27. Since the plant material including any dense starch should a=
nyway have an average density >1g/cc (i.e. greater than plain water*), e=
xcluding any gas spaces, both cases must still
be floating according to some undissolved gas inclusions, though not neces=
sarily the same mix of CO2/O2 in the two cases. You get an A+ for=
industry and design, but
<i>Lemna</i> gets an F for cooperation. </div>
<div><br>
</div>
<div>*Something I=92d not considered that you may know about but I don=92t =
is oil/fat production in plants, which obviously is important for some land=
plants (canola, sesame, olives etc). Oils have specific gr=
avities <1, around 0.9 g/cc, so enough oil volume could
be sufficient to float a water plant without invoking gas spaces. If=
something dense like starch gets converted to an oil in spring, could that=
contribute, or is this just fantasy? </div>
<div><br>
</div>
<div>Is it possible that the trigger for sinking, whatever its mechanism, i=
s a particular drop in day length that had not yet been closely approached =
by Sept 27, and especially in your toasty living room (temperature might be=
another factor)? If you haven=92t
flushed them in frustration, you should convey both your test subjects to =
an unheated outhouse and extend your experiment there at least to freeze-up=
. </div>
<div>Steve </div>
<div>---------------------------------------------------------<br>
<div>
<div>On Sep 27, 2018, at 12:35 PM, David <<a href=3D"mailto:dwebster@gli=
nx.com">dwebster@glinx.com</a>> wrote:</div>
<br class=3D"Apple-interchange-newline">
<blockquote type=3D"cite" class=3D"cite"><style type=3D"text/css"><!--#xc5d=
d5f1fc8d549c blockquote.cite{
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list-style-position:inside;
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#xc5dd5f1fc8d549c{
font-family:Segoe UI;
font-size:12pt;
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<div>
<div>Dear All,</div>
<div> I have had my eye open this summer for some Lemna to tes=
t the gas composition idea; the more soluble CO2 predominating as days shor=
ten leading to flooding of gas spaces and sinking; photosynthesis predomina=
ting in spring as days lengthen leading to
flooded air spaces being filled by less soluble O2 and rise to the surface=
. </div>
<div> And I was able to collect some on Sept 21 with=
out having to wade in muck of uncertain depth. So I set up a simple trial; =
some kept in darkness, except for a few minutes daily for observation, and =
some kept on a windowsill. </div>
<div> By Sept 27 those kept in darkness showed no tendency to =
sink but were noticeably less green than those exposed to daylight and some=
artificial light in the evening. This leads to the conclusion that floodin=
g of intercellular gas spaces when CO2 predominates
does not cause sinking of Lemna. The converse explanation that Lemna=
rises to the surface in the spring when intercellular spaces become filled=
by less soluble O2 is accordingly voided.</div>
<div> The explanation given in the link posted by Nancy on Oct=
3, 2017 is consequently more sound. Starch accumulation in the fall. as ph=
otosynthesis exceeds respiration at lowering temperature, leads to sinking.=
Starch consumption, as temperature warm in
the spring and new buds start to grow, leads to rise to the water surface.=
[density of starch is high; 1.5 g/cm^3]</div>
<div> </div>
<div>Yt, DW, Kentville</div>
<div><br>
</div>
<div> </div>
<div><br>
</div>
<div>------ Original Message ------</div>
<div>From: "Stephen Shaw" <<a href=3D"mailto:srshaw@Dal.Ca">sr=
shaw@Dal.Ca</a>></div>
<div>To: "<a href=3D"mailto:naturens@chebucto.ns.ca">naturens@chebucto=
.ns.ca</a>" <<a href=3D"mailto:naturens@chebucto.ns.ca">naturens@ch=
ebucto.ns.ca</a>></div>
<div>Sent: 3/10/2018 3:20:47 PM</div>
<div>Subject: Re: [NatureNS] Duckweed</div>
<div><br>
</div>
<div id=3D"x20c912178f194f2" style=3D"word-wrap: break-word; -webkit-nbsp-m=
ode: space; -webkit-line-break: after-white-space;">
<blockquote cite=3D"x-msg://4/F3FE0AE5-B951-4A4A-9575-4CE98894C7CA@dal.ca" =
type=3D"cite" class=3D"cite2">
Interesting puzzle, perhaps not so simple. Any cell system like a liv=
e leaf is bound to be somewhat denser than pond water, regardless of denser=
starch, so will naturally sink at all times unless kept buoyant by the ext=
racellular gas bubbles or some other
modification. What seems to need explaining is why the bubbles are m=
aintained in summer (dissolved gases can pass through lipid cell membranes =
quickly, so you=92d expect them to dissolve out into the surrounding pond),=
and why they disappear in winter. He
doesn=92t seem to know if it=92s CO2 or O2 in the bubbles, or both. =
Perhaps they are largely O2 in summer and dissolve and normally pass out of=
the leaf to oxygenate the pond and dissolved CO2 moves in, but leaf photos=
ynthesis is sufficiently high in summer to
maintain them, despite these losses. In winter gas production simply=
stops, and the non-buoyant plants sink. As winter ends, respiration =
produces bubbles with a different gas, CO2, and they rise again then switch=
over to O2 as photosynthesis picks up.
<div><br>
</div>
<div>It therefore seems likely that these leaves have some special surface =
coating that slows down gas exchange with the pond. Maybe they still =
retain stomata under the leaf which normally facilitate gas exchange for le=
aves in air, but these are modified to
block or regulate gas exchange in water? Maybe this is already known=
, just not to us here?</div>
<div>Steve <br>
<br>
<div>
<div>On Mar 10, 2018, at 10:45 AM, David <<a href=3D"mailto:dwebster@gli=
nx.com">dwebster@glinx.com</a>> wrote:</div>
<br class=3D"Apple-interchange-newline">
<blockquote type=3D"cite" class=3D"cite">
<div style=3D"font-family: Tahoma; font-size: 12pt; font-style: normal; fon=
t-variant: normal; font-weight: normal; letter-spacing: normal; line-height=
: normal; orphans: auto; text-align: start; text-indent: 0px; text-transfor=
m: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text=
-stroke-width: 0px;">
<div>Hi Nancy & All,</div>
<div> I admit not having wondered about this but I think he ma=
kes a simple process complicated. The air pockets to which he refers are pr=
esumably intercellular spaces which in the absence of photosynthesis presum=
ably can become water filled. Starch has a
specific gravity of 1.5 g/mL and, in cooler weather starch will accumulate=
when respiration slows more than photosynthesis and the submarine will sin=
k. With warming, growth resumes, respiration and starch consumption rates i=
ncrease and the submarine rises.</div>
<div>Yt, DW, Kentville</div>
<div><br>
</div>
<div>------ Original Message ------</div>
<div>From: "nancy dowd" <<a href=3D"mailto:nancypdowd@gmail.co=
m">nancypdowd@gmail.com</a>></div>
<div>To:<span class=3D"Apple-converted-space"> </span><a href=3D"mailt=
o:naturens@chebucto.ns.ca">naturens@chebucto.ns.ca</a></div>
<div>Sent: 3/10/2018 9:08:02 AM</div>
<div>Subject: [NatureNS] Duckweed</div>
<div><br>
</div>
<div id=3D"xd49ec0a2bdf4406">
<blockquote cite=3D"x-msg://1/A593EEEC-616D-49BA-B70F-CA21003EAEDB@gmail.co=
m" type=3D"cite" class=3D"cite2" style=3D"margin-left: 5px; margin-right: 0=
px; padding-left: 10px; padding-right: 0px; border-left-width: 1px; border-=
left-style: solid; border-left-color: rgb(204, 204, 204); margin-top: 3px; =
padding-top: 0px;">
This is an interesting article on Duckweed seasonal disappearance and reapp=
earance in the Spring 2018 issue of Northern Woodlands Magazine.<a href=3D"=
https://northernwoodlands.org/outside_story/article/duckweed-migration">htt=
ps://northernwoodlands.org/outside_story/article/duckweed-migration</a>
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<div>I had never really thought about where it went in Fall or how it re-em=
erges in Spring. <span style=3D"background-color: rgba(255, 255, 255, =
0);">Such an important floating pond plant in productive fresh water <=
/span><br>
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<div>Nancy D<br>
<br>
<div>Sent from my iPad</div>
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