Leaf optical properties and photosynthesis of fern species with a wide range of divergence time in relation to mesophyll anatomy.

Background And Aims: For a comprehensive understanding of the mechanisms of changing plant photosynthetic capacity during plant evolutionary history, knowledge of leaf gas exchange and optical properties are essential, both of which relate strongly to mesophyll anatomy. Although ferns are suitable for investigating the evolutionary history of photosynthetic capacity, comprehensive research of fern species has yet to be undertaken in this regard.

Methods: We investigated leaf optical properties, gas exchange and mesophyll anatomy of fern species with a wide range of divergence time, using 66 ferns from natural habitats and eight glasshouse-grown ferns.

Effects of sex and soil water chemistry on leaf morphology and physiology of Myrica gale var. tomentosa.

Plants respond to environmental stressors, such as an oligotrophic environments, by altering the morphological and physiological functions of their leaves. Sex affects these functions because of the asymmetric cost of reproduction in dioecious plants. We compared the leaf mass per leaf area (LMA), ratio of intercellular air space in leaf mesophyll tissue (mesophyll porosity), palisade thickness, and carbon isotope ratio (δ13C) of leaves of the dioecious shrub Myrica gale based on sex and gradients of soil water chemistry across habitats in the field.

Three-dimensionally visualized rhizoid system of moss, Physcomitrium patens, by refraction-contrast X-ray micro-computed tomography.

Land plants have two types of shoot-supporting systems, root system and rhizoid system, in vascular plants and bryophytes. However, since the evolutionary origin of the systems is different, how much they exploit common systems or distinct systems to architect their structures is largely unknown. To understand the regulatory mechanism of how bryophytes architect the rhizoid system responding to environmental factors, we have developed the methodology to visualize and quantitatively analyze the rhizoid system of the moss, Physcomitrium patens, in 3D.

How plants grow under gravity conditions besides 1 g: perspectives from hypergravity and space experiments that employ bryophytes as a model organism.

Plants have evolved and grown under the selection pressure of gravitational force at 1 g on Earth. In response to this selection pressure, plants have acquired gravitropism to sense gravity and change their growth direction. In addition, plants also adjust their morphogenesis in response to different gravitational forces in a phenomenon known as gravity resistance.

Overexpressing the HD-Zip class II transcription factor EcHB1 from Eucalyptus camaldulensis increased the leaf photosynthesis and drought tolerance of Eucalyptus.

Alteration in the leaf mesophyll anatomy by genetic modification is potentially a promising tool for improving the physiological functions of trees by improving leaf photosynthesis. Homeodomain leucine zipper (HD-Zip) transcription factors are candidates for anatomical alterations of leaves through modification of cell multiplication, differentiation, and expansion. Full-length cDNA encoding a Eucalyptus camaldulensis HD-Zip class II transcription factor (EcHB1) was over-expressed in vivo in the hybrid Eucalyptus GUT5 generated from Eucalyptus grandis and Eucalyptus urophylla.

A high-performance system of multiple gas-exchange chambers with a laser spectrometer to estimate leaf photosynthesis, stomatal conductance, and mesophyll conductance.

Direct measurements of ecophysiological processes such as leaf photosynthesis are often hampered due to the excessive time required for gas-exchange measurements and the limited availability of multiple gas analyzers. Although recent advancements in commercially available instruments have improved the ability to take measurements more conveniently, the amount of time required for each plant sample to acclimate to chamber conditions has not been sufficiently reduced. Here we describe a system of multiple gas-exchange chambers coupled with a laser spectrometer that employs tunable diode laser absorption spectroscopy (TDLAS) to measure leaf photosynthesis, stomatal conductance, and mesophyll conductance.

Correction to: A hypergravity environment increases chloroplast size, photosynthesis, and plant growth in the moss Physcomitrella patens.

The original article can be found online.

A hypergravity environment increases chloroplast size, photosynthesis, and plant growth in the moss Physcomitrella patens.

The physiological and anatomical responses of bryophytes to altered gravity conditions will provide crucial information for estimating how plant physiological traits have evolved to adapt to significant increases in the effects of gravity in land plant history. We quantified changes in plant growth and photosynthesis in the model plant of mosses, Physcomitrella patens, grown under a hypergravity environment for 25 days or 8 weeks using a custom-built centrifuge equipped with a lighting system. This is the first study to examine the response of bryophytes to hypergravity conditions.

Rapid response of leaf photosynthesis in two fern species Pteridium aquilinum and Thelypteris dentata to changes in CO2 measured by tunable diode laser absorption spectroscopy.

We investigated stomatal conductance (g(s)) and mesophyll conductance (g(m)) in response to atmospheric CO2 concentration [CO2] in two primitive land plants, the fern species Pteridium aquilinum and Thelypteris dentata, using the concurrent measurement of leaf gas exchange and carbon isotope discrimination. [CO2] was initially decreased from 400 to 200 μmol mol(-1), and then increased from 200 to 700 μmol mol(-1), and finally decreased from 700 to 400 μmol mol(-1). Analysis by tunable diode laser absorption spectroscopy (TDLAS) revealed a rapid and continuous response in g m within a few minutes.

The photosynthetic response of tobacco plants overexpressing ice plant aquaporin McMIPB to a soil water deficit and high vapor pressure deficit.

We investigated the photosynthetic capacity and plant growth of tobacco plants overexpressing ice plant (Mesembryanthemum crystallinum L.) aquaporin McMIPB under (1) a well-watered growth condition, (2) a well-watered and temporal higher vapor pressure deficit (VPD) condition, and (3) a soil water deficit growth condition to investigate the effect of McMIPB on photosynthetic responses under moderate soil and atmospheric humidity and water deficit conditions. Transgenic plants showed a significantly higher photosynthesis rate (by 48 %), higher mesophyll conductance (by 52 %), and enhanced growth under the well-watered growth condition than those of control plants.

Effect of overexpression of radish plasma membrane aquaporins on water-use efficiency, photosynthesis and growth of Eucalyptus trees.

Eucalyptus is a diverse genus of flowering trees with more than 700 genotypic species which are mostly native to Australia. We selected 19 wild provenances of Eucalyptus camaldulensis grown in Australia, compared their growth rate and drought tolerance and determined the protein levels of plasma membrane aquaporins (PIPs). There was a positive relationship between the drought tolerance and PIP content.

Barley plasma membrane intrinsic proteins (PIP Aquaporins) as water and CO2 transporters.

We identified barley aquaporins and demonstrated that one, HvPIP2;1, transports water and CO2. Regarding water homeostasis in plants, regulations of aquaporin expression were observed in many plants under several environmental stresses. Under salt stress, a number of plasma membrane-type aquaporins were down-regulated, which can prevent continuous dehydration resulting in cell death.

Expanding roles of plant aquaporins in plasma membranes and cell organelles.

Aquaporins facilitate water transport across biomembranes in a manner dependent on osmotic pressure and water-potential gradient. The discovery of aquaporins has facilitated research on intracellular and whole-plant water transport at the molecular level. Aquaporins belong to a ubiquitous family of membrane intrinsic proteins (MIP).

Relationships between quantum yield for CO2 assimilation, activity of key enzymes and CO2 leakiness in Amaranthus cruentus, a C4 dicot, grown in high or low light.

In C(4) photosynthesis, a part of CO(2) fixed by phosphoenolpyruvate carboxylase (PEPC) leaks from the bundle-sheath cells. Because the CO(2) leak wastes ATP consumed in the C(4) cycle, the leak may decrease the efficiency of CO(2) assimilation. To examine this possibility, we studied the light dependence of CO(2) leakiness (phi), estimated by the concurrent measurements of gas exchange and carbon isotope discrimination, initial activities of ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) and pyruvate, orthophosphate dikinase (PPDK), the phosphorylation state of PEPC and the CO(2) assimilation rate using leaves of Amaranthus cruentus (NAD-malic enzyme subtype, dicot) plants grown in high light (HL) and low light (LL).

Effects of internal conductance on the temperature dependence of the photosynthetic rate in spinach leaves from contrasting growth temperatures.

The photosynthetic rate may be strongly limited by internal conductance from the intercellular airspace to the chloroplast stroma (g(i)). However, the effects of growth and leaf temperature on g(i) are still unclarified. In this work, we determined the temperature dependence of g(i) in spinach leaves grown at 30/25 degrees C (high temperature; HT) and 15/10 degrees C (low temperature; LT), using the concurrent measurements of the gas exchange rate and stable carbon isotope ratio.

Seasonal changes in needle water content and needle ABA concentration of Japanese red pine, Pinus densiflora, in declining forests on Mt. Gokurakuji, Hiroshima prefecture, Japan.

To evaluate the effects of air pollution on the decline of Pinus densiflora forests, various research has been conducted around Mt. Gokurakuji (34 degrees 23'N, 132 degrees 19'E, 693 m a.s.

Irradiance and phenotype: comparative eco-development of sun and shade leaves in relation to photosynthetic CO2 diffusion.

The subject of this paper, sun leaves are thicker and show higher photosynthetic rates than the shade leaves, is approached in two ways. The first seeks to answer the question: why are sun leaves thicker than shade leaves? To do this, CO2 diffusion within a leaf is examined first. Because affinity of Rubisco for CO2 is low, the carboxylation of ribulose 1,5-bisphosphate is competitively inhibited by O2, and the oxygenation of ribulose 1,5-bisphosphate leads to energy-consuming photorespiration, it is essential for C3 plants to maintain the CO2 concentration in the chloroplast as high as possible.

Overexpression of the barley aquaporin HvPIP2;1 increases internal CO(2) conductance and CO(2) assimilation in the leaves of transgenic rice plants.

The internal conductance for CO(2) diffusion (g(i)) and CO(2) assimilation rate were measured and the related anatomical characteristics were investigated in transgenic rice leaves that overexpressed barley aquaporin HvPIP2;1. This study was performed to test the hypothesis that aquaporin facilitates CO(2) diffusion within leaves. The g(i) value was estimated for intact leaves by concurrent measurements of gas exchange and carbon isotope ratio.