scholarly journals Opportunistic survival strategy ofWelwitschia mirabilis: recent anatomical and ecophysiological studies elucidating stomatal behaviour and photosynthetic potential

Botany ◽  
2017 ◽  
Vol 95 (12) ◽  
pp. 1109-1123 ◽  
Author(s):  
G.H.J. Krüger ◽  
A. Jordaan ◽  
L.R. Tiedt ◽  
R.J. Strasser ◽  
M. Kilbourn Louw ◽  
...  
Keyword(s):  
Stomatal Conductance ◽  
Water Conservation ◽  
Root Hairs ◽  
Leaf Tissue ◽  
Severe Drought ◽  
Survival Strategy ◽  
Potted Plants ◽  
New Findings ◽  
Stomatal Apparatus ◽  
Photosynthetic Potential

We present new findings on leaf and stomatal apparatus anatomy and ecophysiology of Welwitschia mirabilis Hook.f. that are relevant to survival in the desert. We show that the structure of the stomatal apparatus with thin areas in the guard cell walls is a key feature enabling an opportunistic survival strategy through reversible quick switch-over from water conservation to CO2assimilation. Desert environment and greenhouse data demonstrated that stomatal conductance increased almost immediately after dawn to reach a maximum within approximately an hour, whereupon a steep decrease occurred. After discontinuation of induced drought in potted plants, fast recovery of stomatal conductance occurred while copious new root hairs developed within 50 h. Stomatal limitation proved to be the main photosynthetic constraint under induced drought. Under severe drought stress, biochemical limitation came into play. Chlorophyll fluorescence data of in-situ plants showed that the photosynthetic potential of leaf tissue is highest near the basal meristem, but although it decreases with age, it retains activity up to the leaf apex at the end of the green part. The photosynthetic potential of potted plants was optimal at 20 °C, analogous to mesophytic plants. Our data confirms our hypothesis that leaf surface and stomatal structure play a crucial role in moisture conservation and moderating leaf temperature for desert survival.

A 2050 Vision for Colorado's water supply future

2012 ◽  
Vol 7 (4) ◽  
Author(s):  
N. Rowan ◽  
E. Hecox ◽  
S. Morea
Keyword(s):  
Water Supply ◽  
Water Conservation ◽  
Colorado River ◽  
Economic Recession ◽  
The State ◽  
Severe Drought ◽  
Water Shortages ◽  
Water Projects ◽  
Demand And Supply ◽  
Local Water

The last decade has brought many changes to Colorado's water supply outlook. Despite the recent economic recession, the state has experienced significant population growth, and Colorado's population is expected to nearly double within the next 40 years. Other pressures on Colorado's water supply include severe drought, a desire to meet multiple needs (i.e., municipal, environmental, recreational) with existing resources, and impacts to agriculture due to water shortages, urbanization, and transfers to new users. To address these challenges, the Colorado Water Conservation Board (CWCB) has undertaken a visioning process to explore solutions to these future water supply challenges. As part of this process, CWCB has led the state in identifying demand and supply strategies to meet the state's future water needs while considering agriculture and the environment. These strategies have been combined into varying portfolios that include methods such as conservation, local water projects, new Colorado River development, and agricultural transfers. This paper details the development and evaluation of these portfolios and describes stakeholder's efforts to balance meeting Colorado's water needs in the future.

Farmer’s Drought Response and Coping Strategies at Household Level in Southern Tigray, Ethiopia

2021 ◽  
Author(s):  
Eskinder Gidey ◽  
Tirhas Gebregergis ◽  
Woldegebrial Zeweld ◽  
Haftamu Gebretsadik ◽  
Ogaile Dikinya ◽  
...  
Keyword(s):  
Coping Strategies ◽  
Water Conservation ◽  
Smallholder Farmers ◽  
Weather Prediction ◽  
Multinomial Logit Model ◽  
Early Warning Systems ◽  
Drought Severity ◽  
Severe Drought ◽  
Household Level ◽  
Household Heads

Abstract Background Drought is one of the most damaging climate-induced threats impacting the lives of many people every year. The purpose of this study was to determine farmer’s drought coping strategies both proactive and reactive responses at household level based on the field survey in Raya Azebo and Raya Chercher districts, southern Tigray, Ethiopia. Agro–climatological based 246 households were sampled from the lowlands (36), midlands (202) and highlands (8). Multinomial logit model was used to identify best drought coping strategies. Results about 24.8% of female headed and 75.2% of male headed respondents have experienced mild to extremely severe drought in the last three decades. A significant association between the various drought severity and household heads (chi–square = 9.861, df = 3, p–value < 0.05) observed. Conclusions this study concluded that collection and saving of pasture, soil and water conservation practices, and use of weather prediction information to adjust saving and farming system are best proactive drought coping strategies. Whereas, feeding of roasted cactus for livestock, borrowing loans for running small business, selling of household assets and reduction of food consumptions are the major reactive or off–farm drought coping strategies in the study area. If the responses of smallholder farmers are not well supported by the concerned bodies, the existing disaster preparedness and early warning systems in the area might be significantly affected and its impacts will be very serious on both the livelihood of local people and natural resources in the area.

scholarly journals GAS EXCHANGE IN YOUNG PLANTS OF Tabebuia aurea(Bignoniaceae Juss.) SUBJECTED TO FLOODING STRESS1

2016 ◽  
Vol 40 (1) ◽  
pp. 39-49 ◽  
Author(s):  
Ademir Kleber Morbeck Oliveira ◽  
Sônia Cristina Juliano Gualtieri
Keyword(s):  
Stomatal Conductance ◽  
Initial Rate ◽  
Co2 Assimilation ◽  
Photosynthesis Rate ◽  
Control Group ◽  
Flooded Soil ◽  
Mato Grosso ◽  
Potted Plants ◽  
Seasonal Flooding ◽  
Mato Grosso Do Sul

ABSTRACT The Paratudo (Tabebuia aurea) is a species occurring in the Pantanal of Miranda, Mato Grosso do Sul, Brazil, an area characterized by seasonal flooding. To evaluate the tolerance of this plant to flooding, plants aged four months were grown in flooded soil and in non-flooded soil (control group). Stomatal conductance, transpiration and CO2 assimilation were measured during the stress (48 days) and recovery (11 days) period, totalling 59 days. The values of stomatal conductance of the control group and stressed plants at the beginning of the flooded were 0.33 mol m-2s-1 and reached 0.02 mol m-2 s-1 (46th day) at the end of this event. For the transpiration parameter, the initial rate was 3.1 mol m s-1, and the final rate reached 0.2 or 0.3 mol m-2 s-1 (47/48 th day). The initial photosynthesis rate was 8.9 mmol m-2s-1 and oscillated after the sixth day, and the rate reached zero on the 48th day. When the photosynthesis rate reached zero, the potted plants were dried, and the rate was analyzed (11th day). The following values were obtained for dried plants: stomatal conductance = 0.26 mol m-2 s-1, transpiration rate = 2.5 mol m-2 s-1 and photosynthesis rate = 7.8 mmol m-2 s-1. Flooded soil reduced photosynthesis and stomatal conductance, leading to the hypertrophy of the lenticels. These parameters recovered and after this period, and plants exhibited tolerance to flooding stress by reducing their physiological activities.

Down-regulation of photosynthesis by drought under field conditions in grapevine leaves

1998 ◽  
Vol 25 (8) ◽  
pp. 893 ◽  
Author(s):  
J. Flexas ◽  
J. M. Escalona ◽  
H. Medrano
Keyword(s):  
Water Stress ◽  
Electron Transport ◽  
Stomatal Conductance ◽  
Stomatal Closure ◽  
General Pattern ◽  
Photochemical Reactions ◽  
Field Conditions ◽  
Down Regulation ◽  
Potted Plants ◽  
Intrinsic Water Use Efficiency

The importance of both stomatal closure and reduced carboxylation efficiency on the photo- synthesis decline in response to long term water stress was previously measured in field-grown grapevines. Here we address the question of whether water stress affects the photochemical capacity of leaves, measuring gas-exchange rates and chlorophyll fluorescence under drought and moderate irrigat- ion at intervals through the summer season during three consecutive years. We conclude that usually water stress does not induce photoinhibition in field-grown grapevines, even when stomatal conductance and photosynthesis are reduced to very low values. Moreover, down-regulat- ion of photochemical reactions is low, leading to a general pattern of photosynthetic response to drought consistent in large reductions of stomatal conductance (g), followed by a consistent decrease of CO2 assimilation (A) but with a much lower effect on electron transport rate (ETR). In consequence, the intrinsic water-use efficiency (A/g) increased, as well as the ratio ETR/A. It is suggested that increased electron transport to alternative pathways, such as photorespiration, prevented further down-regulation of ETR under drought conditions. These results are in agreement with our previous reports for potted plants. However it is clear that, under field conditions with a much more slowly developed water stress, ETR reductions are more attenuated than in potted plants, reducing their incidence in carbon assimilation, which seems to be mainly regulated by stomatal closure.

Water transfer in a mature oak stand (Quercuspetraea): seasonal evolution and effects of a severe drought

1993 ◽  
Vol 23 (6) ◽  
pp. 1136-1143 ◽  
Author(s):  
N. Bréda ◽  
H. Cochard ◽  
E. Dreyer ◽  
A. Granier
Keyword(s):  
Stomatal Conductance ◽  
Potential Evapotranspiration ◽  
Stomatal Closure ◽  
Time Lag ◽  
Xylem Sap ◽  
Water Shortage ◽  
Hydraulic Conductance ◽  
Canopy Conductance ◽  
Severe Drought ◽  
Order Of Magnitude

The reactions of sessile oak (Quercuspetraea (Mattuschka) Liebl.) to drought were studied under natural conditions in a 32-year-old stand near Nancy (northeastern France) during the summers of 1989 (strongly rain deficient) and 1990. A plot of five trees was subjected to imposed water shortage, while a group of irrigated trees was used as a control. Measurements of xylem sap flows and water potential enabled the computation of plot transpiration, canopy conductance, and specific hydraulic conductance in the soil–tree continuum. Stomatal conductance was measured directly with a porometer. Specific hydraulic conductance of our oaks was of the same order of magnitude as that reported for other species. It decreased significantly during spring because of a time lag between cambial growth and leaf area expansion. Measured transpiration was close to potential evapotranspiration, except during days with high vapor pressure deficits, which promoted stomatal closure in the absence of soil water deficits. Imposed drought caused predawn leaf water potentials to reach values as low as −2.0 MPa and a progressive decline in hydraulic conductance, which was probably attributable to modifications in hydraulic properties at the soil–root interface. This gradual decline in conductance was attributed to their deep rooting (1.40 m). This study revealed that Q. petraea may be considered as drought tolerant because of adaptations like deep rooting, efficient and safe xylem sap transport, maintenance of significant stomatal conductance, and significant transpiration, even during strong drought stress.

scholarly journals Generation of guard cell RNA-seq transcriptomes during progressive drought and recovery using an adapted INTACT protocol for Arabidopsis thaliana shoot tissue

2021 ◽  
Author(s):  
Anna van Weringh ◽  
Asher Pasha ◽  
Eddi Esteban ◽  
Paul J. Gamueda ◽  
Nicholas J. Provart
Keyword(s):  
Gene Expression ◽  
Arabidopsis Thaliana ◽  
Drought Stress ◽  
Guard Cell ◽  
Crop Production ◽  
Leaf Tissue ◽  
Cell Types ◽  
Severe Drought ◽  
Data Sets ◽  
Rna Seq

Drought is an important environmental stress that limits crop production. Guard cells (GC) act to control the rate of water loss. To better understand how GCs change their gene expression during a progressive drought we generated guard cell-specific RNA-seq transcriptomes during mild, moderate, and severe drought stress. We additionally sampled re-watered plants that had experienced severe drought stress. These transcriptomes were generated using the INTACT system to capture the RNA from GC nuclei. We optimized the INTACT protocol for Arabidopsis thaliana leaf tissue, incorporating fixation to preserve RNA during nuclear isolation. To be able to identify gene expression changes unique to GCs, we additionally generated transcriptomes from all cell types, using a 35S viral promoter to capture the nuclei of all cell types in leaves. These data sets highlight shared and unique gene expression changes between GCs and the bulk leaf tissue. The timing of gene expression changes is different between GCs and other cell types: we found that only GCs had detectable gene expression changes at the earliest drought time point. The drought responsive GC and leaf RNA-seq transcriptomes are available in the Arabidopsis ePlant at the Bio-Analytic Resource for Plant Biology website.

scholarly journals First Report of a Chaetomella sp. Causing a Leaf Spot on Sansevieria trifasciata in China

Plant Disease ◽  
2013 ◽  
Vol 97 (7) ◽  
pp. 992-992 ◽  
Author(s):  
Y. L. Li ◽  
Z. Zhou ◽  
W. Lu ◽  
J. R. Ye
Keyword(s):  
Leaf Spot ◽  
Disease Incidence ◽  
Morphological Characteristics ◽  
Leaf Tissue ◽  
Aerial Mycelium ◽  
Control Treatment ◽  
Distilled Water ◽  
First Report ◽  
Potted Plants ◽  
Fungal Isolates

Sansevieria trifasciata originates from tropical West Africa. It is widely planted as a potted ornamental in China for improving indoor air quality (1). In February 2011, leaves of S. trifasciata plants in an ornamental market of Anle, Luoyang City, China, were observed with sunken brown lesions up to 20 mm in diameter, and with black pycnidia present in the lesions. One hundred potted plants were examined, with disease incidence at 20%. The symptomatic leaves affected the ornamental value of the plants. A section of leaf tissue from the periphery of two lesions from a plant was cut into 1 cm2 pieces, soaked in 70% ethanol for 30 s, sterilized with 0.1% HgCl2 for 2 min, then washed five times in sterilized distilled water. The pieces were incubated at 28°C on potato dextrose agar (PDA). Colonies of two isolates were brown with submerged hyphae, and aerial mycelium was rare. Abundant and scattered pycnidia were reniform, dark brown, and 200 to 350 × 100 to 250 μm. There were two types of setae on the pycnidia: 1) dark brown setae with inward curved tops, and 2) straight, brown setae. Conidia were hyaline, unicellular, cylindrical, and 3.75 to 6.25 × 1.25 to 2.50 μm. Morphological characteristics suggested the two fungal isolates were a Chaetomella sp. To confirm pathogenicity, six mature leaves of a potted S. trifasciata plant were wounded with a sterile pin after wiping each leaf surface with 70% ethanol and washing each leaf with sterilized distilled water three times. A 0.5 cm mycelial disk cut from the margin of a 5-day-old colony on a PDA plate was placed on each pin-wounded leaf, ensuring that the mycelium was in contact with the wound. Non-colonized PDA discs were placed on pin-wounded leaves as the control treatment. Each of two fungal isolates was inoculated on two leaves, and the control treatment was done similarly on two leaves. The inoculated plant was placed in a growth chamber at 28°C with 80% relative humidity. After 7 days, inoculated leaves produced brown lesions with black pycnidia, but no symptoms developed on the control leaves. A Chaetomella sp. was reisolated from the lesions of inoculated leaves, but not from the control leaves. An additional two potted plants were inoculated using the same methods as replications of the experiment, with identical results. To confirm the fungal identification, the internal transcribed spacer (ITS) region of rDNA of the two isolates was amplified using primers ITS1 and ITS4 (2) and sequenced. The sequences were identical (GenBank Accession No. KC515097) and exhibited 99% nucleotide identity to the ITS sequence of an isolate of Chaetomella sp. in GenBank (AJ301961). To our knowledge, this is the first report of a leaf spot of S. trifasciata caused by Chaetomella sp. in China as well as anywhere in the world. References: (1) X. Z. Guo et al. Subtropical Crops Commun. Zhejiang 27:9, 2005. (2) T. J. White et al. PCR Protocols: A Guide to Methods and Applications. M. A. Innis et al., eds. Academic Press, San Diego, CA, 1990.

scholarly journals Woody Litter Increases Headwater Stream Metal Export Ratio in an Alpine Forest

Forests ◽  
2019 ◽  
Vol 10 (5) ◽  
pp. 379
Author(s):  
Ziyi Liang ◽  
Fuzhong Wu ◽  
Xiangyin Ni ◽  
Bo Tan ◽  
Li Zhang ◽  
...  
Keyword(s):  
Water Conservation ◽  
Headwater Streams ◽  
Regional Climate ◽  
Plant Litter ◽  
Alpine Forest ◽  
Export Ratio ◽  
New Findings ◽  
Woody Litter ◽  
Forest Streams ◽  
And Storage

Headwater streams have low productivity and are closely linked to forest ecosystems, which input a large amount of plant litter into streams. Most current studies have focused on the decomposition process of plant litter in streams, and the effects of non-woody and woody litter on metal transfer, accumulation, and storage in streams are poorly understood. Here, we addressed how non-woody and woody litter affect metals in headwater streams in an alpine forest on the Eastern Tibetan Plateau. This area is the source of many rivers and plays an important regulatory role in the regional climate and water conservation. Through comparisons of five metal concentrations, exports and storage in headwater streams with different input conditions of plant litter, our results showed that the input of woody litter could significantly increase flow discharge and increase the metal export ratio in the water. Similarly, the input of non-woody litter could reduce the metal concentration in the water and facilitate the stable storage of metals in the sediment in the headwater streams. Therefore, allochthonous non-woody and woody litter can affect the concentration of metals in water and sediment, and the transfer and accumulation of metals from upstream to downstream in headwater streams. This study provides basic data and new findings for understanding the effects of allochthonous plant litter on the accumulation and storage of metals in headwater forest streams and may provide new ideas for assessing and managing water quality in headwater streams in alpine forests.

scholarly journals Field Damage to Yellow Starthistle Infected by Synchytrium solstitiale, and Greenhouse Maintenance and Host Range of the Fungus

Plant Disease ◽  
2011 ◽  
Vol 95 (8) ◽  
pp. 907-912
Author(s):  
F. M. Eskandari ◽  
W. L. Bruckart ◽  
T. L. Widmer
Keyword(s):  
United States ◽  
Biological Control ◽  
Host Range ◽  
Leaf Tissue ◽  
The United States ◽  
Carthamus Tinctorius ◽  
Yellow Starthistle ◽  
Potted Plants ◽  
Host Range Determination ◽  
Range Determination

Yellow starthistle (YST, Centaurea solstitialis) is a major weed pest of the western United States. Synchytrium solstitiale, a pathogen of YST, caused significant damage to symptomatic (versus asymptomatic) plants in a field study in France. Before it was evaluated as a candidate for biological control of YST in the United States, protocols for pathogen maintenance under greenhouse conditions were developed. Maintenance, increase, and host range determination protocols involved incubation at 10/15°C (night/day) with an 8-h photoperiod either of potted or exhumed (i.e., roots of 4-week-old plants grown in flasks of water) plants inoculated with galled leaf tissue, or potted plants in which inoculum was wrapped within healthy leaves by a plastic wrap. The leaf-wrap protocol, used during the host range determination, always resulted in disease of YST. Several safflower (Carthamus tinctorius) cultivars and other plants related to YST became diseased following this protocol, thus raising concern about host specificity. Development of disease on nontarget species precludes proposal of S. solstitiale for biological control of YST at this time.

scholarly journals IS ABSCISIC ACID INVOLVED IN THE DROUGHT RESPONSES OF BRAZILIAN GREEN DWARF COCONUT?

2009 ◽  
Vol 45 (2) ◽  
pp. 189-198 ◽  
Author(s):  
F. P. GOMES ◽  
M. A. OLIVA ◽  
M. S. MIELKE ◽  
A-A. F. DE ALMEIDA ◽  
H. G. LEITE ◽  
...  
Keyword(s):  
Abscisic Acid ◽  
Water Stress ◽  
Stomatal Conductance ◽  
Gas Exchange ◽  
Water Potential ◽  
Water Use ◽  
Severe Drought ◽  
Use Efficiency ◽  
Recovery Cycles ◽  
Mild Drought

SUMMARYAbscisic acid (ABA) accumulation in leaves of drought-stressed coconut palms and its involvement with stomatal regulation of gas exchange during and after stress were investigated. Two Brazilian Green Dwarf coconut ecotypes from hot/humid and hot/dry environments were submitted to three consecutive drying/recovery cycles under greenhouse conditions. ABA accumulated in leaflets before significant changes in pre-dawn leaflet water potential (ΨPD) and did not recover completely in the two ecotypes after 8 days of rewatering. Stomatal conductance was influenced by ABA under mild drought and by ΨPD under severe drought. There were no significant differences between the ecotypes for most variables measured. However, the ecotype from a hot/dry environment showed higher water use efficiency after repeated cycles of water stress.

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