scholarly journals Hydraulic architecture of seedlings and adults of Rhizophora mangle L. in fringe and scrub mangrove

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Diana J. Cisneros-de la Cruz ◽  
Laura Yáñez-Espinosa ◽  
Casandra Reyes-García ◽  
Roberth Us-Santamaría ◽  
José Luis Andrade
Keyword(s):  
Water Potential ◽  
Soil Water Potential ◽  
Biosphere Reserve ◽  
Rhizophora Mangle ◽  
Conduction System ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Hydraulic Architecture ◽  
Mangrove Plant ◽  
Wide Range

Background: Mangrove plant species have distinctive anatomical and physiological responses to cope with a wide range of salinities and inundations. These strategies pertain a safe and efficient water use and transport, essential for survival. Questions: How are the anatomical and physiological attributes of the hydraulic architecture of seedlings and adults of Rhizophora mangle? what are the changes in hydraulic architecture of seedlings and adults of R. mangle in contrasting microenvironments? Studied species: Rhizophora mangle L. (Rhizophoraceae). Study site and dates: Scrub and fringe mangroves in Ria Celestún Biosphere Reserve, during the rainy season of 2013 (July to October). Methods: Hydraulic conductivity and leaf water potential, as well as xylem vessel density, length, transversal and radial diameter, and area were measured for seedlings and adults from both sites. The prevailing environmental conditions (soil water potential, salinity, photon flux density, air temperature and relative humidity) were also characterized. Results: A safer hydraulic conduction system, with narrow and more grouped vessels, was observed in seedlings than in adults of R. mangle in both sites. Adult individuals from the scrub mangrove, in the hyper saline microenvironment, had a safer hydraulic conduction system than adults in the fringe mangrove. Conclusions: The seedling stage of R. mangle showed a safer hydraulic system than adults in both types of mangroves. However, over time this hydraulic conduction system could become more efficient or remain safe depending on the microenvironment in which individuals are growing.

Effects of salal understory removal on photosynthetic rate and stomatal conductance of young Douglas-fir trees

1986 ◽  
Vol 16 (1) ◽  
pp. 90-97 ◽  
Author(s):  
D. T. Price ◽  
T. A. Black ◽  
F. M. Kelliher
Keyword(s):  
Stomatal Conductance ◽  
Water Potential ◽  
Soil Water ◽  
Soil Water Potential ◽  
Vapour Pressure Deficit ◽  
Basal Area ◽  
Douglas Fir ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Data Set

The effects of salal (Gaultheriashallon Pursh.) understory removal on the growth of thinned 32-year-old Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) trees were determined in a stand subject to growing season soil water deficits. Four pairs of similar trees were selected and the understory was completely removed from around one of each pair, the root zones of which were both isolated using plastic sheeting buried to bedrock. Photosynthesis, stomatal conductance, soil water potential and canopy microclimate were measured intensively in one pair on 4 clear days during an extended dry period in June 1982. Basal area increment of the four pairs of trees was measured over three growing seasons. To determine the effect of soil water potential on tree photosynthesis, the same variables were intensively measured over 3 consecutive days in late August 1982 for another tree initially subjected to a soil water potential of approximately −1.6 MPa, but irrigated to approximately −0.02 MPa between the 1st and 2nd days. Solar irradiance decreased markedly between the 2nd and 3rd days, thereby creating a unique data set. Findings were as follows: (i) removal of understory significantly increased rates of photosynthesis in the trees, both diurnally and seasonally, (ii) photosynthesis was not generally limited by stomatal conductance unless vapour pressure deficit was high and photon flux density was saturating, and (iii) tree growth response to salal removal was due to higher soil water potential, which increased both photosynthetic capacity and stomatal conductance.

New plant hydraulic architecture reproduces impacts of droughts in the Amazon rainforest

2021 ◽  
Author(s):  
Phillip Papastefanou ◽  
Christian Zang ◽  
Thomas Pugh ◽  
Daijun Liu ◽  
David Lapola ◽  
...  
Keyword(s):  
Water Potential ◽  
Leaf Water Potential ◽  
Leaf Water ◽  
Amazon Rainforest ◽  
Hydraulic Architecture ◽  
Vegetation Model ◽  
Dynamic Global Vegetation Model ◽  
Plant Hydraulics ◽  
Wide Range ◽  
Carbon Losses

<p>The Amazon rainforest has been hit by extreme drought events in recent decades. Thereby, plant hydraulics are essential to better understand the impacts of droughts on single plants and whole forest ecosystems. Plant hydraulic mechanisms such as stomatal closure and leaf water potential are very complex, still posing challenges for current vegetation model development and parameterization. Here, we present the new hydraulic architecture of the Dynamic Global Vegetation Model LPJ-GUESS, accounting for leaf stomatal responses to plant water status and subsequent drought-induced mortality. We show that when applying the model to the Amazon rainforest we can reproduce the observed increasing trend in carbon losses and the decreasing trend in net carbon sink from plot observations over the past two decades. Our model simulations suggest that the increasing historical trend in carbon losses from mortality can be explained by hydraulic failure and associated mortality.</p><p>The high biodiversity of the Amazon tropical rainforest poses further challenges for process-based models. Here we present an approach to include the diversity of plant responses to drought by simulating 37 individual Plant Functional Types (PFTs) differing in their leaf water potential regulation- and resistance to soil water stress, and provide a simple solution how to cover a wide range of species and species-specific parameters. Future modelling studies should also take species interaction and competition of different hydraulic strategies into account.</p>

What Limits the Efficiency of Photosynthesis, and Can There Be Beneficial Improvements?

1998 ◽  
Author(s):  
J. Barber
Keyword(s):  
Carbon Dioxide ◽  
Molecular Mechanisms ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Sufficient Information ◽  
A Value ◽  
Wide Range ◽  
Rate Of Photosynthesis ◽  
Main Factors

Over the past 35 years a great deal has been learned about the mechanisms of photosynthesis, ranging from the ultrafast reactions involved in the initial capture of photons to the slower processes of carbon metabolism. Today our knowledge of photosynthesis and its molecular mechanisms is enormous, so much so that it is difficult for one person to absorb all the information. This is not necessarily a bad thing, since what we have achieved is sufficient information to appreciate the complexity of the “photosynthetic engine” and to identify the main factors that ultimately regulate its efficiency. In this chapter I summarize those areas of photosynthesis research with which I am reasonably familiar and, in so doing, address the question posed by the chapter title. As Blackman (1895a,b) pointed out, the rate of photosynthesis initially rises as the light intensity is increased and then levels off to a plateau. This plot is often referred to as the rate v PFD curve, where PFD stands for Photon Flux Density. Over the years rigorous analyses of the slopes of the rate v PFD curve have been made to obtain a value of the quantum yield (usually expressed as the number of quanta or photons required to produce one molecule of oxygen or to fix one molecule of carbon dioxide). With a few exceptions, the value obtained for a wide range of “non stressed” organisms and plants supplied with excess CO2 is about 9 or a little more (Björkman and Demmig, 1987; Walker, 1992). Bearing in mind that one molecule of oxygen evolved or carbon dioxide fixed is a 4e/4H+ process, then a value of 8 would he consistent with the “Z-scheme” model proposed by Hill and Bendall (1960). In this scheme, each electron is excited twice, first by photosystem two (PSII) and then by photosystem one (PSI). In this way, 8 photons are used to drive 4e/4H+ from water, through PSII and PSI to NADP.

scholarly journals A Chlorophyll Fluorescence-based Biofeedback System to Control Photosynthetic Lighting in Controlled Environment Agriculture

2016 ◽  
Vol 141 (2) ◽  
pp. 169-176 ◽  
Author(s):  
Marc W. van Iersel ◽  
Geoffrey Weaver ◽  
Michael T. Martin ◽  
Rhuanito S. Ferrarezi ◽  
Erico Mattos ◽  
...  
Keyword(s):  
Chlorophyll Fluorescence ◽  
Ipomoea Batatas ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Controlled Environment ◽  
Fluorescence Measurements ◽  
Subsequent Decrease ◽  
Biofeedback System ◽  
Wide Range ◽  
Controlled Environment Agriculture

Photosynthetic lighting is one of the main costs of running controlled environment agriculture facilities. To optimize photosynthetic lighting, it is important to understand how plants use the provided light. When photosynthetic pigments absorb photons, the energy from those photons is used to drive the light reactions of photosynthesis, thermally dissipated, or re-emitted by chlorophyll as fluorescence. Chlorophyll fluorescence measurements can be used to determine the quantum yield of photosystem II (ΦPSII) and nonphotochemical quenching (NPQ), which is indicative of the amount of absorbed light energy that is dissipated as heat. Our objective was to develop and test a biofeedback system that allows for the control of photosynthetic photon flux density (PPFD) based on the physiological performance of the plants. To do so, we used a chlorophyll fluorometer to measure ΦPSII, and used these data and PPFD to calculate the electron transport rate (ETR) through PSII. A datalogger then adjusted the duty cycle of the light-emitting diodes (LEDs) based on the ratio of the measured ETR to a predefined target ETR (ETRT). The biofeedback system was able to maintain ETRs of 70 or 100 µmol·m−2·s−1 over 16-hour periods in experiments conducted with lettuce (Lactuca sativa). With an ETRT of 70 µmol·m−2·s−1, ΦPSII was stable throughout the 16 hour and no appreciable changes in PPFD were needed. At an ETRT of 100 µmol·m−2·s−1, ΦPSII gradually decreased from 0.612 to 0.582. To maintain ETR at 100 µmol·m−2·s−1, PPFD had to be increased from 389 to 409 µmol·m−2·s−1, resulting in a gradual decrease of ΦPSII and an increase in NPQ. The ability of the biofeedback system to achieve a range of different ETRs within a single day was tested using lettuce, sweetpotato (Ipomoea batatas), and pothos (Epipremnum aureum). As the ETRT was gradually increased, the PPFD required to achieve that ETR also increased, whereas ΦPSII decreased. Surprisingly, a subsequent decrease in ETRT, and in the PPFD required to achieve that ETR, resulted in only a small increase in ΦPSII. This indicates that ΦPSII was reduced because of photoinhibition. Our results show that the biofeedback system is able to maintain a wide range of ETRs, while it also is capable of distinguishing between NPQ and photoinhibition as causes for decreases in ΦPSII.

scholarly journals Water relations and hydraulic architecture in Cerrado trees: adjustments to seasonal changes in water availability and evaporative demand

2008 ◽  
Vol 20 (3) ◽  
pp. 233-245 ◽  
Author(s):  
Sandra J. Bucci ◽  
Fabian G. Scholz ◽  
Guillermo Goldstein ◽  
Frederick C. Meinzer ◽  
Augusto C. Franco ◽  
...  
Keyword(s):  
Water Potential ◽  
Water Relations ◽  
Seasonal Changes ◽  
Soil Water Potential ◽  
Woody Species ◽  
Dry Season ◽  
Hydraulic Architecture ◽  
Wet Season ◽  
Evaporative Demand ◽  
Water Deficits

We determined adjustments in physiology and morphology that allow Neotropical savanna trees from central Brazil (Cerrado) to avoid water deficits and to maintain a nearly constant internal water balance despite seasonal changes in precipitation and air saturation deficit (D). Precipitation in the study area is highly seasonal with about five nearly rainless months during which D is two fold higher compared to wet season values. As a consequence of the seasonal fluctuations in rainfall and D, soil water potential changes substantially in the upper 100 cm of soil, but remains nearly constant below 2 m depth. Hydraulic architecture and water relations traits of Cerrado trees adjusted during the dry season to prevent increasing water deficits and insure homeostasis in minimum leaf water potential ψL and in total daily water loss per plant (isohydry). The isohydric behavior of Cerrado trees was the result of a decrease in total leaf surface area per tree, a strong stomatal control of evaporative losses, an increase in leaf-specific hydraulic conductivity and leaf hydraulic conductance and an increase in the amount of water withdrawn from internal stem storage, during the dry season. Water transport efficiency increased in the same proportion in leaves and terminal stems during the dry season. All of these seasonal adjustments were important for maintaining ψL above critical thresholds, which reduces the rate of embolism formation in stems and help to avoid turgor loss in leaf tissues still during the dry season. These adjustments allow the stems of most Cerrado woody species to operate far from the point of catastrophic dysfunction for cavitation, while leaves operate close to it and experience embolism on a daily basis, especially during the dry season.

scholarly journals Comparison of the Photoautotrophic Growth Regimens of Chlorella sorokiniana in a Photobioreactor for Enhanced Biomass Productivity

Biology ◽  
2020 ◽  
Vol 9 (7) ◽  
pp. 169
Author(s):  
Elvira E. Ziganshina ◽  
Svetlana S. Bulynina ◽  
Ayrat M. Ziganshin
Keyword(s):  
Large Scale ◽  
Basal Medium ◽  
Biomass Productivity ◽  
Chlorella Sorokiniana ◽  
Pigment Concentration ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Total Biomass ◽  
Initial Growth ◽  
Wide Range

Microalgae have a wide industrial potential because of their high metabolic diversity and plasticity. Selection of optimal cultivation methods is important to optimize multi-purpose microalgal biotechnologies. In this research, Chlorella sorokiniana AM-02 that was isolated from a freshwater lake was cultured under various high photosynthetic photon flux density (PPFD) conditions and CO2 gas levels in standard Bold’s basal medium (BBM). Furthermore, a wide range of nitrate levels (180–1440 mg L−1) was tested on the growth of C. sorokiniana. Microalgae growth, pigment concentration, medium pH, exit gas composition, as well as nitrate, phosphate, and sulfate levels were measured during an experimental period. The preferred high PPFD and optimal CO2 levels were found to be 1000–1400 μmol photons m−2 s−1 and 0.5–2.0% (v/v), respectively. The addition of nitrate ions (up to 1440 mg L−1) to the standard growth medium increased final optical density (OD750), cell count, pigment concentration, and total biomass yield but decreased the initial growth rate at high nitrate levels. Our findings can serve as the basis for a robust photoautotrophic cultivation system to maximize the productivity of large-scale microalgal cultures.

Parthenium weed (Parthenium hysterophorus L.): gas exchange characteristics as a basis for prediction of its geographical distribution

1977 ◽  
Vol 28 (3) ◽  
pp. 449 ◽  
Author(s):  
D Doley
Keyword(s):  
Gas Exchange ◽  
Water Potential ◽  
Gas Phase ◽  
Leaf Water Potential ◽  
Dark Respiration ◽  
Leaf Water ◽  
Parthenium Hysterophorus ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Very High

Gas exchange studies in Parthenium hysterophorus L., a weed recently introduced into central Queensland, indicate that its limits of distribution may be very wide in the humid and subhumid regions of Australia. Under conditions of high leaf water potential, the maximum rate of apparent photosynthesis of cabinet-grown plants was 77 ng cm-2 sec-1, with a temperature optimum of 28°C. Gas phase diffusive resistances were very low and insensitive to photosynthetic photon flux density at high water potentials (–5.0 bars), but became greater and quite sensitive to photon flux as the leaf water potential approached –20 bars. At temperatures between 10 and 40°C, transpiration increased slightly, and the dark respiration rate was almost constant, owing to a steady and considerable increase in gas phase diffusive resistance with temperature. The control of gas exchange broke down at about 42°C, so that transpiration in the light and dark proceeded at equal rates, and dark respiration rates were very high. Gas exchange in P. hysterophorus appears to be no more sensitive to reduced water potential than it is in several favoured crop and pasture species, but the distribution of this weed may be limited by even brief exposure to very high temperatures, or by prolonged drought.

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