next message in archive
next message in thread
previous message in archive
previous message in thread
Index of Subjects
year..whereas other years it was everywhere.<div><br></div><div>He --Apple-Mail-66BB6B86-E0E5-4116-A0EB-ADC09109B9D4 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Interesting. That must have had something to do with the drought conditions d= uring the growing season in 2016 (?). =20 Nancy Sent from my iPad > On Mar 12, 2018, at 2:40 PM, Helene Van Doninck <helene.birdvet@gmail.com>= wrote: >=20 > Having raised many waterfowl chicks at CWRC last summer, we always include= duckweed in their diet and we had to look HARD for it last year..whereas ot= her years it was everywhere. >=20 > Helene >=20 > Helene Van Doninck DVM > Cobequid Wildlife Rehabilitation Centre > 2220 Irwin Lake Rd Brookfield NS Canada B0N1C0 > 902-893-0253 > helene.birdvet@gmail.com > www.cwrc.net > Find us on Facebook and Twitter > ****Wildlife Matters**** >=20 >=20 >> On Sat, Mar 10, 2018 at 5:42 PM, N Robinson <nrobbyn@gmail.com> wrote: >> Interesting discussion - thank you! =20 >>=20 >> And then there is Wikipedia re interesting research going on: https://en= .wikipedia.org/wiki/Lemnoideae >>=20 >> "Duckweed is being studied by researchers around the world as a possible s= ource of clean energy. In the United States, in addition to being the subjec= t of study by the DOE, both Rutgers University and North Carolina State Univ= ersity have ongoing projects to determine whether duckweed might be a source= of cost-effective, clean, renewable energy.[18][19] Duckweed is a good cand= idate as a biofuel because it grows rapidly, produces five to six times as m= uch starch as corn per unit of area, and does not contribute to global warmi= ng.[20][21] Unlike fossil fuels, duckweed removes carbon dioxide from the at= mosphere instead of adding it.[22]" >>=20 >> Nancy >>=20 >>=20 >>> On Sat, Mar 10, 2018 at 3:52 PM, David <dwebster@glinx.com> wrote: >>> Hi Steven & All, >>> Good points. Aquatic plants typically have specialized tissues of i= nterconnected passages which are filled with gas when the plant is active an= d I would expect this to be true of Lemna also. The relative solubility of C= O2 and O2 in water is no doubt relevant; CO2 is 16.4 and 31.5 times as solub= le in water as O2 at 0o C and 10oC respectively. So during the growing seaso= n, photosynthesis would keep such aerenchyma filled with O2. With shorter da= ys and less photosynthesis, CO2 production by respiration (year round in al= l living tissue night and day) would gradually exceed O2 production and lead= to a flooding of the ballast tanks as the CO2 dissolves; submarine down.=20= >>> No doubt details of the anatomy play a part but I would expect stoma= ta if present to be on the upper surface. >>> Yt, DW,Kentville >>> =20 >>>=20 >>> ------ Original Message ------ >>> From: "Stephen Shaw" <srshaw@Dal.Ca> >>> To: "naturens@chebucto.ns.ca" <naturens@chebucto.ns.ca> >>> Sent: 3/10/2018 3:20:47 PM >>> Subject: Re: [NatureNS] Duckweed >>>=20 >>>> Interesting puzzle, perhaps not so simple. Any cell system like a live= leaf is bound to be somewhat denser than pond water, regardless of denser s= tarch, so will naturally sink at all times unless kept buoyant by the extrac= ellular gas bubbles or some other modification. What seems to need explaini= ng is why the bubbles are maintained in summer (dissolved gases can pass thr= ough lipid cell membranes quickly, so you=E2=80=99d expect them to dissolve o= ut into the surrounding pond), and why they disappear in winter. He doesn=E2= =80=99t seem to know if it=E2=80=99s CO2 or O2 in the bubbles, or both. Per= haps 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 photosynthe= sis is sufficiently high in summer to maintain them, despite these losses. I= n winter gas production simply stops, and the non-buoyant plants sink. As w= inter ends, respiration produces bubbles with a different gas, CO2, and they= rise again then switch over to O2 as photosynthesis picks up. =20 >>>>=20 >>>> It therefore seems likely that these leaves have some special surface c= oating that slows down gas exchange with the pond. Maybe they still retain s= tomata under the leaf which normally facilitate gas exchange for leaves in a= ir, but these are modified to block or regulate gas exchange in water? Mayb= e this is already known, just not to us here? >>>> Steve =20 >>>>=20 >>>>> On Mar 10, 2018, at 10:45 AM, David <dwebster@glinx.com> wrote: >>>>>=20 >>>>> Hi Nancy & All, >>>>> I admit not having wondered about this but I think he makes a simp= le process complicated. The air pockets to which he refers are presumably in= tercellular spaces which in the absence of photosynthesis presumably can bec= ome water filled. Starch has a specific gravity of 1.5 g/mL and, in cooler w= eather starch will accumulate when respiration slows more than photosynthesi= s and the submarine will sink. With warming, growth resumes, respiration and= starch consumption rates increase and the submarine rises. >>>>> Yt, DW, Kentville >>>>>=20 >>>>> ------ Original Message ------ >>>>> From: "nancy dowd" <nancypdowd@gmail.com> >>>>> To: naturens@chebucto.ns.ca >>>>> Sent: 3/10/2018 9:08:02 AM >>>>> Subject: [NatureNS] Duckweed >>>>>=20 >>>>>> This is an interesting article on Duckweed seasonal disappearance and= reappearance in the Spring 2018 issue of Northern Woodlands Magazine.https:= //northernwoodlands.org/outside_story/article/duckweed-migration >>>>>>=20 >>>>>> I had never really thought about where it went in Fall or how it re-e= merges in Spring. Such an important floating pond plant in productive fresh w= ater=20 >>>>>>=20 >>>>>> Nancy D >>>>