Astartekløft stratigraphic log (A) (after [5]; [25]) compared to area changes showed as box plots in the measured fossil taxa: <i>Elatocladus</i> (B); <i>Podozamites</i> (C); <i>Baiera</i> (D); <i>Ginkgoites</i> (E); <i>Anomozamites</i> (F); <i>Pterophyllum</i> (G).

<p>Astartekløft stratigraphic log (A) (after <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0060614#pone.0060614-Hesselbo1" target="_blank">[5]</a>; <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0060614#pone.0060614-McElwain2" target="_blank">[25]</a>) compared to area changes showed as box plots in the measured fossil taxa: <i>Elatocladus</i> (B); <i>Podozamites</i> (C); <i>Baiera</i> (D); <i>Ginkgoites</i> (E); <i>Anomozamites</i> (F); <i>Pterophyllum</i> (G).</p

Comparison of atmospheric CO₂ changes and timing of potential high SO₂ with measured changes to fossil leaf relative abundance and shape factor at Astartekløft.

<p>Atmospheric CO₂ changes at Astartekløft <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0060614#pone.0060614-Steinthorsdottir1" target="_blank">[4]</a> with the time of suggested likely high SO₂<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0060614#pone.0060614-Schaller1" target="_blank">[3]</a>; <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0060614#pone.0060614-Mander1" target="_blank">[34]</a> superimposed as grey (A) compared to shape factor changes as box plots and relative abundance changes as bars for each of the measured fossil taxa <i>Elatocladus</i> (B); <i>Podozamites</i> (C); <i>Baiera</i> (D); <i>Ginkgoites</i> (E); <i>Anomozamites</i> (F); <i>Pterophyllum</i> (G).</p

Examples of leaf physiognomy for each nearest living equivalent species in the study.

<p><i>Lepidozamia peroffskyana</i> (A); <i>Lepidozamia hopei</i> (B); <i>Nageia nagi</i> (C); <i>Agathis australis</i> (D); <i>Ginkgo biloba</i> (E). Lower case Roman numerals indicate the simulated palaeoatmospheric treatment that the leaf grew in: (i) control; (ii) elevated SO₂ and (iii) Tr–J type atmosphere. The scale bar in each image is 10 mm.</p

Summary of atmospheric changes compared to standing fossil richness recorded at Astartekløft and SO₂ responsiveness of both fossil and NLE taxa.

<p>Astartekløft stratigraphic log (A) (after <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0060614#pone.0060614-Hesselbo1" target="_blank">[5]</a>; <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0060614#pone.0060614-McElwain2" target="_blank">[25]</a>) compared to atmospheric CO₂ changes (B) <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0060614#pone.0060614-Steinthorsdottir1" target="_blank">[4]</a> with timing of likely high SO₂<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0060614#pone.0060614-Schaller1" target="_blank">[3]</a>; <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0060614#pone.0060614-Mander1" target="_blank">[34]</a> superimposed in grey, standing species richness (C) <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0060614#pone.0060614-McElwain2" target="_blank">[25]</a> and summarized responsiveness of both fossil and NLE taxa (D).</p

Box plots showing the range of values for area and shape factor for each nearest living equivalent species.

<p>The box represents the lower 25 percentile, the median value and the upper 25% percentile and the whiskers represent the range of the data. Stars represent outliers (values over twice the value of the median). <i>Lepidozamia hopei</i> (A area and B shape factor); L. <i>peroffskyana</i> (C area and D shape factor); <i>Agathis australis</i> (E area and F shape factor); <i>Nageia nagi</i> (G area and H shape factor); <i>Ginkgo biloba</i> (I area and J shape factor).</p

Photosynthetic Diffusional Constraints Affect Yield in Drought Stressed Rice Cultivars during Flowering

<div><p>Global production of rice (<i>Oryza sativa</i>) grain is limited by water availability and the low ‘leaf-level’ photosynthetic capacity of many cultivars. <i>Oryza sativa</i> is extremely susceptible to water-deficits; therefore, predicted increases in the frequency and duration of drought events, combined with future rises in global temperatures and food demand, necessitate the development of more productive and drought tolerant cultivars. We investigated the underlying physiological, isotopic and morphological responses to water-deficit in seven common varieties of <i>O. sativa</i>, subjected to prolonged drought of varying intensities, for phenotyping purposes in open field conditions. Significant variation was observed in leaf-level photosynthesis rates (<i>A</i>) under both water treatments. Yield and <i>A</i> were influenced by the conductance of the mesophyll layer to CO₂ (<i>g</i>_m) and not by stomatal conductance (<i>g</i>_s). Mesophyll conductance declined during drought to differing extents among the cultivars; those varieties that maintained <i>g</i>_m during water-deficit sustained <i>A</i> and yield to a greater extent. However, the variety with the highest <i>g</i>_m and yield under well-watered conditions (IR55419-04) was distinct from the most effective cultivar under drought (Vandana). Mesophyll conductance most effectively characterises the photosynthetic capacity and yield of <i>O. sativa</i> cultivars under both well-watered and water-deficit conditions; however, the desired attributes of high <i>g</i>_m during optimal growth conditions and the capacity for <i>g</i>_m to remain constant during water-deficit may be mutually exclusive. Nonetheless, future genetic and physiological studies aimed at enhancing <i>O. sativa</i> yield and drought stress tolerance should investigate the biochemistry and morphology of the interface between the sub-stomatal pore and mesophyll layer.</p></div

Kruskal Wallis and Mann-Whitney pair-wise comparisons for each physiognomic trait in <i>Ginkgo biloba</i> in the different simulated palaeoatmospheric treatments.

<p>Kruskal Wallis and Mann-Whitney pair-wise comparisons for each physiognomic trait in <i>Ginkgo biloba</i> in the different simulated palaeoatmospheric treatments.</p

Kruskal Wallis and Mann-Whitney pair-wise comparisons for each physiognomic trait in <i>Agathis australis</i> in the different simulated palaeoatmospheric treatments.

<p>Kruskal Wallis and Mann-Whitney pair-wise comparisons for each physiognomic trait in <i>Agathis australis</i> in the different simulated palaeoatmospheric treatments.</p

Measurements of (a) the intercellular [CO₂] (<i>C</i>_i) to the ambient [CO₂] (<i>C</i>_a) ratio (<i>C</i>_i/<i>C</i>_a), and (b) the chloroplastic [CO₂] (<i>C</i>_c) to the ambient [CO₂] ratio (<i>C</i>_c/<i>C</i>_a) in control and water-stressed leaves of the seven <i>Oryza sativa</i> genotypes.

<p>The measurements were made on the flag leaf in saturating PPFD (1400 µmol m⁻²s⁻¹), with relative humidity ranging between 45–55%, and a leaf temperature of 30°C. Data are means of 4 to 7 plants per treatment. Error bars as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0109054#pone-0109054-g001" target="_blank">Figure 1</a>. Different letters denote significant differences among means derived using a factorial ANOVA and Tukey <i>post-hoc</i> test.</p

Changes in yield and photosynthesis in relation to modification of diffusive resistances to CO₂ uptake following water-stress.

<p>Those varieties that experienced smaller reductions in parameters were more tolerant of drought. a) relationship between Δyield and Δ<i>g</i>_s (linear regression: R² = 0.337; <i>F</i>_1,4 = 2.032; <i>P</i> = 0.227); b) relationship between Δyield and Δ<i>g</i>_m (linear regression: R² = 0.134; <i>F</i>_1,4 = 0.618; <i>P</i> = 0.476); c) relationship between Δyield and Δ<i>g</i>_tot (linear regression: R² = 0.0818; <i>F</i>_1,4 = 0.356; <i>P</i> = 0.583); d) relationship between Δ<i>A</i> and Δ<i>g</i>_s (linear regression: R² = 0.0003; <i>F</i>_1,4 = 0.00106; <i>P</i> = 0.976); e) relationship between Δ<i>A</i> and Δ<i>g</i>_m (linear regression: R² = 0.742; <i>F</i>_1,4 = 11.527; <i>P</i> = 0.0274); f) relationship between Δ<i>A</i> and Δ<i>g</i>_tot (linear regression: R² = 0.715; <i>F</i>_1,4 = 10.042; <i>P</i> = 0.0339), and; g) relationship between Δyield and Δ<i>A</i> (linear regression: R² = 0.427; <i>F</i>_1,4 = 2.979; <i>P</i> = 0.159). Error bars as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0109054#pone-0109054-g001" target="_blank">Figure 1</a>. Numbers next to data points indicate <i>Oryza sativa</i> variety as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0109054#pone-0109054-g001" target="_blank">Figure 1</a>.</p