scholarly journals Evolution of C 4 plants: a new hypothesis for an interaction of CO 2 and water relations mediated by plant hydraulics

2012 ◽  
Vol 367 (1588) ◽  
pp. 583-600 ◽  
Author(s):  
Colin P. Osborne ◽  
Lawren Sack
Keyword(s):  
Water Relations ◽  
High Light ◽  
Soil Conditions ◽  
Evolutionary Transitions ◽  
Physiological Models ◽  
Plant Hydraulics ◽  
Selective Agents ◽  
Environmental Transitions ◽  
Rate Of Photosynthesis ◽  
New Hypothesis

C 4 photosynthesis has evolved more than 60 times as a carbon-concentrating mechanism to augment the ancestral C 3 photosynthetic pathway. The rate and the efficiency of photosynthesis are greater in the C 4 than C 3 type under atmospheric CO 2 depletion, high light and temperature, suggesting these factors as important selective agents. This hypothesis is consistent with comparative analyses of grasses, which indicate repeated evolutionary transitions from shaded forest to open habitats. However, such environmental transitions also impact strongly on plant–water relations. We hypothesize that excessive demand for water transport associated with low CO 2 , high light and temperature would have selected for C 4 photosynthesis not only to increase the efficiency and rate of photosynthesis, but also as a water-conserving mechanism. Our proposal is supported by evidence from the literature and physiological models. The C 4 pathway allows high rates of photosynthesis at low stomatal conductance, even given low atmospheric CO 2 . The resultant decrease in transpiration protects the hydraulic system, allowing stomata to remain open and photosynthesis to be sustained for longer under drying atmospheric and soil conditions. The evolution of C 4 photosynthesis therefore simultaneously improved plant carbon and water relations, conferring strong benefits as atmospheric CO 2 declined and ecological demand for water rose.

Rates of Photosynthesis Relative to Activity of Photosynthetic Enzymes, Chlorophyll and Soluble Protein Content Among Ten C4 Species

1984 ◽  
Vol 11 (6) ◽  
pp. 509 ◽  
Author(s):  
H Usuda ◽  
MSB Ku ◽  
GE Edwards
Keyword(s):  
Leaf Area ◽  
Soluble Protein ◽  
High Light ◽  
Soluble Protein Content ◽  
Bisphosphate Carboxylase ◽  
Unit Leaf ◽  
C4 Species ◽  
Photosynthetic Enzymes ◽  
Rate Of Photosynthesis ◽  
High Degree

Among 10 C4 species having a wide range in photosynthetic activity, the rates of photosynthesis/leaf area under high light were examined and compared with the chlorophyll and soluble protein content and the activities of several photosynthetic enzymes. The species examined were Digitaria sanguinalis, Echinochloa crus-galli, Microstegium vimineum, Panicum capillare, Panicum miliaceum, Paspalum dilatatum, Paspalum notatum, Pennisetum purpureum, Setaria lutescens, and Zea mays. The photosynthetic rates per unit leaf area ranged from 10 to 38 �mol CO2 fixed m-2 s-1. Among the 10 species there was a high degree of correlation of rate of photosynthesis/leaf area with soluble protein (r = 0.88), ribulose 1,5-bisphosphate carboxylase (r = 0.88) and pyruvate,PI dikinase (r = 0.94), but a lower correlation of photosynthetic rate/leaf area with phosphoenolpyruvate carboxylase (r = 0.74) and no significant correlation of photosynthetic rate/leaf area with chlorophyll content (r = 0.56). Among eight species of the NADP-malic enzyme C4 subgroup, there was a good correlation of photosynthetic ratelleaf area with NADP-malate dehydrogenase (r = 0.88) and NADP- malic enzyme (r = 0.92). Extractable activities of both the ribulose 1,5-bisphosphate carboxylase and the dikinase were generally close to the rate of photosynthesis. When comparing the activity per unit leaf area of one enzyme with another, generally a high degree of correlation was found among the species. The results suggest that a given C4 species tends to maintain a balance in the activities of several photosynthetic enzymes and that there is potential to estimate capacity for C4 photosynthesis under high light through determining activity of certain photosynthetic enzymes.

scholarly journals Plant hydraulic traits reveal islands as refugia from worsening drought

2020 ◽  
Vol 8 (1) ◽  
Author(s):  
Aaron R Ramirez ◽  
Mark E De Guzman ◽  
Todd E Dawson ◽  
David D Ackerly
Keyword(s):  
Climate Change ◽  
Water Relations ◽  
Plant Traits ◽  
Regional Climate ◽  
Channel Islands ◽  
Local Conditions ◽  
Early 21St Century ◽  
Plant Hydraulics ◽  
Drought Conditions ◽  
Potential Climate Change

Abstract Relatively mesic environments within arid regions may be important conservation targets as ‘climate change refugia’ for species persistence in the face of worsening drought conditions. Semi-arid southern California and the relatively mesic environments of California’s Channel Islands provide a model system for examining drought responses of plants in potential climate change refugia. Most methods for detecting refugia are focused on ‘exposure’ of organisms to certain abiotic conditions, which fail to assess how local adaptation or acclimation of plant traits (i.e. ‘sensitivity’) contribute to or offset the benefits of reduced exposure. Here, we use a comparative plant hydraulics approach to characterize the vulnerability of plants to drought, providing a framework for identifying the locations and trait patterns that underlie functioning climate change refugia. Seasonal water relations, xylem hydraulic traits and remotely sensed vegetation indices of matched island and mainland field sites were used to compare the response of native plants from contrasting island and mainland sites to hotter droughts in the early 21st century. Island plants experienced more favorable water relations and resilience to recent drought. However, island plants displayed low plasticity/adaptation of hydraulic traits to local conditions, which indicates that relatively conserved traits of island plants underlie greater hydraulic safety and localized buffering from regional drought conditions. Our results provide an explanation for how California’s Channel Islands function as a regional climate refugia during past and current climate change and demonstrate a physiology-based approach for detecting potential climate change refugia in other systems.

The basics of plant hydraulics

2014 ◽  
Vol 1 ◽  
pp. e001
Author(s):  
Hervé Cochard
Keyword(s):  
Water Relations ◽  
Gas Exchanges ◽  
Short Text ◽  
Plant Hydraulics

This short text gives the fundamentals of plant hydraulics and its impact of their water relations and gas exchanges.

Extended maternal care and offspring interactions in the subsocial Australian crab spider, Xysticus bimaculatus

2016 ◽  
Vol 64 (5) ◽  
pp. 344 ◽  
Author(s):  
Marlis Dumke
Keyword(s):  
Maternal Care ◽  
Group Living ◽  
Group Cohesion ◽  
Suitable Model ◽  
Evolutionary Transitions ◽  
Selective Agents ◽  
Maternal Presence ◽  
Communal Feeding ◽  
Extended Maternal Care ◽  
Crab Spider

Extended maternal care is considered a prerequisite for the evolution of permanent family grouping and eusociality in invertebrates. In spiders, the essential evolutionary transitions to permanent sociality along this ‘subsocial route’ include the extension of care beyond hatching, the persistence of offspring groups to maturation and the elimination of premating dispersal. Subsocial Australian crab spiders (Thomisidae) present a suitable system to identify the selective agents prolonging group cohesion. Particularly, the recent discovery of independently evolved subsociality in the thomisid Xysticus bimaculatus provides new potential for comparative studies to expand the limited understanding of group cohesion beyond the offspring’s potential independence and despite socially exploitative behaviour. Providing fundamental knowledge, the present study investigated maternal care and offspring interactions in X. bimaculatus for the first time. Nest dissections revealed that mothers produce exceptionally small clutches, potentially reflecting a limit in the number of juveniles they can successfully care for. A laboratory experiment demonstrated crucial benefits for offspring in receiving maternal care beyond nutritional independence, mediated by extensive maternal food provisioning. However, prey-sharing also occurred between juveniles irrespective of maternal presence, which marks this species’ predisposition for exploitative feeding behaviour. I therefore suggest X. bimaculatus as a suitable model for investigating the regulation of communal feeding in group-living spiders.

Photosynthetic characteristics of a purple sulfur bacterium grown under different light intensities

1972 ◽  
Vol 18 (12) ◽  
pp. 1825-1828 ◽  
Author(s):  
M. Takahashi ◽  
K. Shiokawa ◽  
S. Ichimura
Keyword(s):  
Light Intensity ◽  
Photosynthetic Rate ◽  
Photosynthetic Characteristics ◽  
High Light ◽  
Bacteriochlorophyll A ◽  
Low Light ◽  
Purple Sulfur Bacterium ◽  
Light Intensities ◽  
Rate Of Photosynthesis ◽  
Structural Mechanisms

Photosynthetic characteristics of a purple sulfur bacterium, Chromatium, strain D, cultured under various light intensities were examined. With a decrease in the light intensity used for culture, the bacteriochlorophyll a content per unit cell nitrogen increased. Also, at low light intensities, the rate of photosynthesis (per unit bacteriochlorophyll a) was higher in samples grown under low light than in those grown under high light. These two responses to low light intensity are adaptations that ensure a high photosynthetic rate for the purple sulfur bacterium that usually occurs in a dimly lit environment. Possible chemical and structural mechanisms involved are discussed.

scholarly journals Black and Chestnut Oak Seedling Response to Glaciated Soil: Implications for Northward Expansion in Response to Climate Warming

2019 ◽  
Vol 65 (5) ◽  
pp. 637-643
Author(s):  
Lauren S Pile ◽  
Joanne Rebbeck ◽  
Patrick H Brose ◽  
Robert P Long
Keyword(s):  
Climate Warming ◽  
Carbon Sink ◽  
Net Photosynthesis ◽  
High Light ◽  
Soil Conditions ◽  
Low Light ◽  
Species Response ◽  
Light Levels ◽  
Mycorrhizal Association ◽  
Oak Seedlings

Abstract Species ranges are expected to move northward with climate warming. However, species will likely encounter soil conditions that differ from their historic ranges. Black (Quercus velutina) and chestnut (Q. montana) oaks are expected to do well in climates that are hotter and drier, but it is unknown as to how they respond to soils of different geological histories. At a glaciated and nonglaciated site in northwestern Pennsylvania, we compared the growth, biomass allocation, and mycorrhizal association for black and chestnut oak seedlings at two different levels of light. On nutrient-poor, nonglaciated soils at high light levels, both species had greater growth and biomass accumulation than on nutrient-rich, glaciated soils. However, at low light levels, these responses were greatest on glaciated soils, especially for chestnut oak. Although mycorrhizal association was beneficial on nonglaciated soil at high light levels, low light levels were associated with reduced growth when compared to glaciated soils. In low light and nutrient-poor soils, mycorrhizal association may result in a carbon sink with lower net photosynthesis, as carbon for plant growth is, instead, allocated to the mycorrhizae symbiont. Variable species response to soil types indicates reduced performance for black and chestnut oak seedlings on high-quality glaciated soils especially in high light environments.

Enhanced water relations of residual foliage following defoliation in Populus tremuloides

2000 ◽  
Vol 78 (5) ◽  
pp. 583-590 ◽  
Author(s):  
Miranda Hart ◽  
E H Hogg ◽  
V J Lieffers
Keyword(s):  
Stomatal Conductance ◽  
Water Potential ◽  
Water Relations ◽  
Leaf Water Potential ◽  
Populus Tremuloides ◽  
Vapour Pressure ◽  
Leaf Water ◽  
Controlled Conditions ◽  
Rate Of Photosynthesis ◽  
Compensatory Photosynthesis

Stomatal conductance and leaf water potential of aspen (Populus tremuloides Michx.) were measured in response to defoliation intensity, both in the field and under controlled conditions. There was evidence of increased stomatal conductance in trees with 50 and 98% defoliation, but no change in leaf water potential. Under controlled conditions, stomatal conductance and rate of photosynthesis were measured under high and low vapour pressure deficits (VPD). Under high VPD, overall stomatal conductance and rates of photosynthesis were greatly reduced. However, in both VPD treatments, there was evidence of increased stomatal conductance and compensatory photosynthesis following defoliation. These findings may be due to increases in leaf specific hydraulic conductance following defoliation.Key words: defoliation, stomatal conductance, leaf water potential, compensatory photosynthesis.

Statistical patterns of carbonates and total organic carbon on soils of Tuber rufum and T. melanosporum (black truffle) brûlés

Soil Research ◽  
2009 ◽  
Vol 47 (2) ◽  
pp. 206 ◽  
Author(s):  
L. G. García-Montero ◽  
I. Valverde-Asenjo ◽  
P. Díaz ◽  
C. Pascual
Keyword(s):  
Organic Carbon ◽  
Total Organic Carbon ◽  
Principal Component ◽  
Soil Conditions ◽  
Carbonate Content ◽  
Black Truffle ◽  
Total Carbonate ◽  
The Mean ◽  
New Hypothesis ◽  
Mean Concentration

The ascocarps of several truffle species, such as Tuber rufum, are harvested in T. melanosporum brûlés; these species reduce T. melanosporum production. Some authors argue that this competition might be due to the evolution of organic matter in the soil. However, soil conditions in brûlés have yet to be clarified, and most studies on T. melanosporum fail to supply statistical data. We propose a study of 40 soils to compare the values for total organic carbon (TOC), pH, and carbonates inside the brûlés with the values for the outer edges of the same brûlés, where T. rufum ascocarps are collected. A principal component analysis relates the soils from the inner brûlés with high active carbonate content and soils outside the brûlés with high TOC and total carbonate content. ANOVA analyses indicate that the mean concentration of active carbonate, total CO32–, and % active/total carbonate differ significantly depending on soil location, but there are no significant differences for pH and TOC. These results lead us to propose a new hypothesis: T. melanosporum mycelia may solubilise active carbonate (<50 μm) and the other carbonate fractions (>50 μm) inside the brûlés; however the environmental conditions of the brûlés could favour a secondary carbonate precipitation with a net increase in active carbonate. This increase would counterbalance carbonate losses from leaching, which would in turn favour T. melanosporum mycelia, suggesting a feedback process.

Inhibition of photosynthesis by low oxygen concentrations

1981 ◽  
Vol 59 (5) ◽  
pp. 721-725 ◽  
Author(s):  
P. B. E. McVetty ◽  
D. T. Canvin
Keyword(s):  
Oxygen Concentration ◽  
High Light ◽  
Low Oxygen ◽  
Low Light ◽  
Light Intensities ◽  
Oxidation Reduction ◽  
Transport Chain ◽  
Rate Of Photosynthesis ◽  
Effect Of Oxygen ◽  
Temporary Inhibition

The effect of changing the oxygen concentration from 21 to 2% on photosynthesis of wheat, sunflower, and soybean was investigated. At low CO2 concentrations and low light intensities, a stimulation of photosynthesis was observed in 2% oxygen compared with the rate in 21% O2. At high CO2 concentrations and high light intensities, a temporary inhibition of photosynthesis was observed when the oxygen concentration was changed from 21 to 2%. In wheat and sunflower, this inhibition was observed at progressively lower CO2 concentrations as temperatures were decreased. In soybean only, a slight inhibition of photosynthesis was observed at higher temperatures. In some cases, especially in plants grown under a low light intensity, a long-lasting (> 45 min) inhibition of photosynthesis was observed. In most cases, however, the inhibition lasted only for several minutes and final rates of photosynthesis in 2% O2 were equal to or greater than the rate of photosynthesis in 21% O2. The stimulatory effect of oxygen on photosynthesis at high CO2 concentrations and high light intensities could possibly be due to a regulation of the oxidation–reduction state of the electron transport chain and the maintenance of phosphorylation.

Sign in / Sign up

Export Citation Format

Share Document