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NewPaper 2Phytologist Research 325Table 2 Maximum net photosynthesis (NP), chlorophyll (chl), total phosphorus (TP) and total nitrogen (TN) content of Lobelia leaves inrelation to DW, sediment organic content and pore-water concentrations of Fe 2+ and dissolved inorganic carbon (DIC) at 4 cm depth after80 d of experiments with sandy sediments receiving 0 and 0.8% labile organic matter in Lake Värsjö from 10 July to 1 OctoberTreatment Photosynthesis Leaf contentSedimentcompositionPore waterOrganic matteradded (%)NP (lmolO 2 g )1 DW h )1 )Chl (mgg )1 DW)TP (mgg )1 DW)TN (mgg )1 DW)Organiccontent (%) Fe 2+ (lM) DIC (mM)0.0 282 ± 18 2.47 ± 0.34 1.62 ± 0.26 23.2 ± 4.32 0.66 ± 0.10 16.0 ± 5.61 1.03 ± 0.540.8 64 ± 17 0.99 ± 0.15 0.89 ± 0.02 11.3 ± 2.21 0.81 ± 0.03 1204 ± 381 4.78 ± 0.95Mean ± SD, n =3.(a)(b)(c)they rapidly went anoxic and stayed anoxic for several hoursin the dark. Daytime O 2 in leaf lacunae of Lobelia on sedimentsenriched with 1.6% organic matter never exceeded20 kPa after 40 d into the experiment and O 2 disappearedmore rapidly in the dark than in the 0.4% organic treatment.The duration of leaf anoxia during the 12 h dark periodwas significantly positively correlated to % organic matteradded (Spearman’s r, P < 0.01, joint analysis of all measurements;Fig. 4). As root morphology changed anddegradation of organic matter progressed towards the endof the experiment, the anoxic period in leaf lacunae in thedark declined to 1.8 h on control sediments and to 5.9 and6.6 h on sediments enriched with 0.4 and 1.6% organicmatter, respectively (Fig. 4). The decline of the anoxicperiod with time of the experiment was systematic in alltreatments, although not statistically significant.Field experiments with Lobelia populations in lateAugust under the same temperatures, a 13 : 11 h light :dark cycle and higher daytime irradiance displayed the samediurnal O 2 course in leaf lacunae and sediment pore waterat 1 cm depth as in laboratory experiments (Fig. 5). Thus,O 2 in the sediment reached 20–23 kPa (close to 100%saturation) late in the afternoon and vanished for 1–6 h latein the night. In the leaf lacunae, O 2 peaked at 22–31 kPalate in the afternoon and vanished for 1–3 h late in thenight.Fig. 2 Diurnal changes of O 2 partial pressure (PO 2 ) in leaf lacunaeof Lobelia (solid line), sediment pore water at 10 mm depth (dashedline) and water phase (dotted line) in laboratory experiments in thecontrol (a), 0.4% (b) and 1.6% (c) treatments after 4, 9 and 7 d ofenrichment, respectively. The diurnal trace started with a shift from12 h light to 12 h darkness followed by a shift back to 12 h light.Values are single measurements.Chlorophyll content and photosynthesisChlorophyll content and photosynthesis at saturating lightand CO 2 changed in concert across organic enrichments andover time in laboratory experiments (Fig. 6). Chlorophyllcontent and maximum photosynthesis were highest and atapproximately the same level among organic enrichments18 d into the experiment. A small increase of both chlorophyllcontent and photosynthesis sometimes occurred atlow organic enrichment (0.1 and 0.2%); however, whenomitting the control treatment from the dataset, both variablessubsequently declined significantly (linear regression,Ó 2010 The AuthorsNew Phytologist Ó 2010 New Phytologist Trust46New Phytologist (2011) 190: 320–331www.newphytologist.com
326 ResearchPaper 2NewPhytologist(a)(b)Fig. 4 Duration of anoxia during the 12 h dark period in leaf lacunaeof Lobelia as a function of time after addition of different amountsof labile organic matter (circles, control; squares, 0.4%; diamonds,1.6% of added organic matter to sediments). Different plants fromeach treatment were used for measurements over time (n = 1).(c)(d)P < 0.05) across the range of organic enrichments. Photosynthesisdropped to very low amounts in the 1.6% organicenrichment.For all leaf samples among treatments and over time,chlorophyll content was significantly positively related totissue concentrations of TN and almost so to TP (linearregression, P = 0.06, Table 3). Chlorophyll was significantlynegatively related to TFe because some leaves fromthe 1.6% organic treatment had surface plaques of Fe. TPand TN were also significantly interrelated. Photosynthesiswas highly significantly related to chlorophyll, TP and TNin the leaves, while it was significantly negatively related toTFe (Table 3). Also in field experiments, photosynthesis,chlorophyll, TN and TP declined significantly with 0.8%organic enrichment (t-test, P < 0.01; Table 2).Fig. 3 Diurnal changes in O 2 partial pressure (PO 2 ) in leaf lacunaeof Lobelia with increasing time into the experiment (a, 4–9 d; b, c.40 d; c, c.73d;d,c. 150 d (control and 1.6%) and 111 d (0.4%))for plants growing in the laboratory in sediments with 0% (control,solid line), 0.4% (dashed line) and 1.6% addition (dotted line) oflabile organic matter per sediment DW. Data in (a) are derived fromFig. 2. The diurnal trace started with a shift from 12 h light to 12 hdarkness followed by a shift back to 12 h light. Different plants fromeach treatment were used for measurements over time, n =1.Root development and leaf nutrientsMaximum root length declined from c. 7.1 ± 1.6 cm incontrol sediments to only 4.3 ± 0.5 cm in the organicallyrichest sediments deprived of O 2 in laboratory experiments.Across the organic enrichment gradient, the ratio of leaflength to root length increased fourfold from 0.53 ± 0.1in the control to 1.89 ± 0.1 in the 1.6% organic mattertreatment (Table 3).Total phosphorus and TN in leaf tissue changed profoundlyamong treatments and over time in both laboratoryand field experiments (Fig. 7, Table 2). The highest andmost constant leaf concentrations occurred in plants fromcontrol sediments, but progressively lower TP and TNconcentrations occurred with duration of the experimentand higher addition of organic matter despite increasingnutrient concentrations in the sediments (Tables 1, 2).New Phytologist (2011) 190: 320–331www.newphytologist.com47Ó 2010 The AuthorsNew Phytologist Ó 2010 New Phytologist Trust
Page 1: Oxygen dynamics and plant-sedimenti
Page 5: PrefaceThe content of this thesis i
Page 9: AbstractAbstract● Isoetids occupy
Page 13 and 14: IntroductionIntroductionOligotrophi
Page 15 and 16: Introductionwater (Wigand et al. 19
Page 17 and 18: IntroductionSand-Jensen K, Prahl C,
Page 19 and 20: Thesis summaryThesis summaryAdditio
Page 21 and 22: Thesis summaryFig. 4. Chlorophyll c
Page 23: Thesis summaryascribed to lack of A
Page 27: Paper 1Oxygen, carbon and iron dyna
Page 30 and 31: Paper 1extensive sediment volume by
Page 32 and 33: Paper 1method of Andersen (1976) an
Page 35 and 36: Paper 1Table 3. Retention of added
Page 37 and 38: Paper 1recalcitrant organic pools a
Page 39: Paper 2High sensitivity of Lobelia
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Page 55 and 56: Paper 3Higher gas permeability of l
Page 57 and 58: Paper 3Here, we perform a parallel
Page 59 and 60: Paper 3Fig. 1. O 2 penetration dept
Page 61 and 62: Paper 3Table 2. O 2 flux across lea
Page 63 and 64: Paper 3Fig. 4. Leaf chlorophyll of
Page 65 and 66: Paper 3high internal concentrations
Page 67 and 68: Paper 3Colmer TD 2003. Long-distanc
Page 69: Paper 4Organic enrichment of sedime
Page 72 and 73: Paper 4Surveys on aquatic plants re
Page 74 and 75: Paper 4ensure mixing and air satura
Page 76 and 77: Paper 4ResultsFig 1. O 2 -penetrati
Page 78 and 79: Paper 4Table 2. Individual leaf bio
Page 80 and 81: Paper 4Fig. 4. Root density (○) a
Page 82 and 83: Paper 4hours every night although l
Page 84 and 85: Paper 4Møller CL, Sand-Jensen K. 2
Page 87 and 88: [Plant Signaling & Behavior 3:10, 8
Page 89: Outstanding Lobelia dortmanna in ir
Page 93 and 94: Planterødders overlevelse ivanddæ
Page 95 and 96: Paper 6Figur 3. Aflejringer af lign
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Paper 6Vi har sat planterødders ve
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