Mechanisms of adaptation to drought

 

Ecophysiological adaptations of water relations of Teucrium chamaedrys L. to the hot and dry climate of xeric limestone sites in Franconia (Southern Germany)

by Burghardt M., Burghardt A., Rosenberger C., Riederer M. (2008)

in Flora – Volume 203, Issue 1, 15 January 2008, Pages 3–13

doi:10.1016/j.flora.2007.11.003

Abstract

Teucrium chamaedrys is a typical plant of dry grassland communities at xeric sites on calcareous soils in Franconia (Southern Germany). The morphological–anatomical appearance of limestone plants in the form of nanism or dwarfing has been interpreted by Gregor Kraus approximately 100 years ago as a consequence of the dry and hot environmental conditions.

In the present study the mechanisms of adaptation to drought were evaluated by comparison of water relations of plants growing in the natural habitat at a xeric site in the nature protection area “Grainberg-Kalbenstein und Saupurzel” with plants cultivated at a mesic site in the Botanical Garden of the University of Würzburg.

Cuticular water permeances of astomatous leaf sides and minimum conductances of detached leaves were not significantly different between the two growing regimes indicating that there are no intraspecific/phenotypic adaptations in terms of the establishment of a more efficient cuticular transpiration barrier and a more strict regulation of the stomatal aperture as response to the xeric conditions of the limestone site. Pressure–volume analysis of water potential revealed that plants growing at the xeric site exhibited a lower water potential at the turgor loss point and a higher bulk modulus of elasticity.

Both parameters emphasise the ability to regain more rapidly a favourable water status at drought by water uptake from the soil and to maintain turgor at lower water potentials. Gas exchange measurements obtained from attached leaves of intact plants under controlled experimental conditions in the laboratory revealed that under drought stress, at water potentials far below the turgor loss point, stomata were only completely closed in the dark. In the light the water loss by stomatal transpiration contributed with values between 60% and 75% to the total water loss. This physiological response was found both for plants grown at the xeric site and plants cultivated at the mesic site.

The maintenance of a low but still measurable stomatal conductance under drought stress at maximum light intensity can be interpreted as a mechanism to adjust leaf temperature below the heat resistance limit by transpiration cooling.

See the text: Science Direct

Bryophyte stomatal responsiveness to atmospheric CO2

Photo credit: AoB Blog

Stomatal density and aperture in non-vascular land plants are non-responsive to above-ambient atmospheric CO2 concentrations

by Field K. J., Duckett J. G., Cameron D. D., Pressel S. (2015)

in Annals of Botany, 115 (6). 915 – 922. -http://dx.doi.org/10.1093/aob/mcv021

Abstract

BACKGROUND AND AIMS:

Following the consensus view for unitary origin and conserved function of stomata across over 400 million years of land plant evolution, stomatal abundance has been widely used to reconstruct palaeo-atmospheric environments. However, the responsiveness of stomata in mosses and hornworts, the most basal stomate lineages of extant land plants, has received relatively little attention.

This study aimed to redress this imbalance and provide the first direct evidence of bryophyte stomatal responsiveness to atmospheric CO2.

METHODS:

A selection of hornwort (Anthoceros punctatus, Phaeoceros laevis) and moss (Polytrichum juniperinum, Mnium hornum, Funaria hygrometrica) sporophytes with contrasting stomatal morphologies were grown under different atmospheric CO2 concentrations ([CO2]) representing both modern (440 p.p.m. CO2) and ancient (1500 p.p.m. CO2) atmospheres. Upon sporophyte maturation, stomata from each bryophyte species were imaged, measured and quantified.

KEY RESULTS:

Densities and dimensions were unaffected by changes in [CO2], other than a slight increase in stomatal density in Funaria and abnormalities in Polytrichum stomata under elevated [CO2].

CONCLUSIONS: The changes to stomata in Funaria and Polytrichum are attributed to differential growth of the sporophytes rather than stomata-specific responses. The absence of responses to changes in [CO2] in bryophytes is in line with findings previously reported in other early lineages of vascular plants. These findings strengthen the hypothesis of an incremental acquisition of stomatal regulatory processes through land plant evolution and urge considerable caution in using stomatal densities as proxies for paleo-atmospheric CO2 concentrations.

See the text: White Rose

Stomata in Arum (Araceae)

 

Stomata in some species of genus Arum from the Eastern Slavonia and Baranya region

by Sabo M., Marček T., Bačić T., Krstin L., Lendel A. (2007)

===

in Biologia 62(4): 409–415

ISSN (Online) 1336-9563, ISSN (Print) 0006-3088 -DOI: 10.2478/s11756-007-0084-6

Abstract

Types and the number of stomata in the following Arum species: Arum italicum Mill., Arum maculatum var. maculatum L. and Arum maculatum var. immaculatum L., Arum alpinum var. pannonicum Terpo. and Arum alpinum var. intermedium Schur. in three different locations in Zablaće, Normanci and Bilje were investigated.

The most prevalent stomata type at both upper and lower epidermis for each Arum species was mostly stomata type paracytic, followed by hexacytic, tetracytic or brachyparacytic as far as locality is concerned. Helicocytic type was more prevalent in Arum alpinum var. pannonicum Terpo. and Arum alpinum var. intermedium Schur. at Bilje. Other stomata types were very rare.

A striking regularity in the occurrence of stomata types was not found within a single species. Some stomata types, however, were found either at adaxial or abaxial epidermis or were not present at all. The number of stomata per square mm varied from 25 to 651. A statistically significant difference in the number of stomata per square mm at upper and lower epidermis among Arum species was determined in locations Zablaće and Normanci, whereas no statistically significant differences were found in location Bilje.

See the text: De Gruyter

 

 

Stomata in Vandoideae (Orchidaceae)

Comparative anatomical and stomatal studies of some taxa of group Vandoideae

by Vattakandy L. S., Chaudhari G. S., Pandey P.O. (2014)

===

in BIOINFOLET – A Quarterly Journal of Life Sciences 11(1a): 122-126 
Print ISSN : 0973-1431. Online ISSN : 0976-4755.

Abstract

The paper presents anatomical features of the aerial root, stem, leaf and stoma of three species of Acampe rigida Roxb., Rhynchostylis retusa (Linn.) Blume and Vanda tessellate (Roxb.) Hook belonging to the tribe Vandeae including the subtribe Aeridinae.

The prominent characters of the epiphytes were 4 to 5 layers of velamen cells, uniseriate exodermis with U-thickened cell walls and collateral vascular bundles in roots. The raphid bundles occurred in roots and leaves. Endodermal cells are O and U-thickened. Sunken stomata with anisocytic, paracytic and stomatal chambers were observed. The vascular bundles in leaves occurred in single series with alternating large and small bundles. The leaf, root, stem and floral elements showed amphistomatic, homogenous mesophyll with aerial spaces.

See the text: Indian Journals.com

Positive relationship between pCO2 and stomatal frequency

 

A new positive relationship between pCO2 and stomatal frequency in Quercus guyavifolia (Fagaceae): a potential proxy for palaeo-CO2 levels

by Hu J.-J., Xing Y.-W., Turkington R., Jacques F. M. B., Su T., Huang Y.-J., Zhou Z.-K. (2015)

in Annals of Botany 115: 777-788

Background and Aims

The inverse relationship between atmospheric CO2 partial pressure (pCO2) and stomatal frequency in many species of plants has been widely used to estimate palaeoatmospheric CO2 (palaeo-CO2) levels; however, the results obtained have been quite variable.

This study attempts to find a potential new proxy for palaeo-CO2 levels by analysing stomatal frequency in Quercus guyavifolia (Q. guajavifolia, Fagaceae), an extant dominant species of sclerophyllous forests in the Himalayas with abundant fossil relatives.

Methods

Stomatal frequency was analysed for extant samples of Q. guyavifolia collected from17 field sites at altitudes ranging between 2493 and 4497 m. Herbarium specimens collected between 1926 and 2011 were also examined. Correlations of pCO2–stomatal frequency were determined using samples from both sources, and these were then applied to Q. preguyavaefolia fossils in order to estimate palaeo-CO2 concentrations for two late-Pliocene floras in south-western China.

Key Results

In contrast to the negative correlations detected for most other species that have been studied, a positive correlation between pCO2 and stomatal frequency was determined in Q. guyavifolia sampled from both extant field collections and historical herbarium specimens. Palaeo-CO2 concentrations were estimated to be approx. 180–240 ppm in the late Pliocene, which is consistent with most other previous estimates.

Conclusions

A new positive relationship between pCO2 and stomatal frequency in Q. guyavifolia is presented, which can be applied to the fossils closely related to this species that are widely distributed in the late-Cenozoic strata in order to estimate palaeo-CO2 concentrations. The results show that it is valid to use a positive relationship to estimate palaeo-CO2 concentrations, and the study adds to the variety of stomatal density/index relationships that available for estimating pCO2. The physiological mechanisms underlying this positive response are unclear, however, and require further research.

See the text: Oaks of the Americas

To use stomatal characters as aid in taxonomy (dicots)

 

COMPARATIVE STUDIES IN STOMATA OF A MEDICINALLY IMPORTANT PLANT CASSIA ANGUSTIFOLIA GROWN IN DIFFERENT SOIL TREATMENTS

by Singanaboina K. , Chinna V., Ratnampally S. K. (2015)

in International Journal of Institutional Pharmacy and Life Sciences 5(3): May-June 2015 – (ISSN): 2249-6807

ABSTRACT

The stomatal diversity (size, shape, types and orientation) in the foliar epidermis has great value in plant systematic studies. The present paper deals with the comparative studies of stomatal structure of Cassia angustifolia which were grown in three different soils.

Leaf epidermal studies mainly stomatal, costal, leaf clearings and articular preparations were examined with light microscope. The study is based on the type of stomata present in the epidermal surface, stomatal index and costal cell shape, epidermal cell shape in leaves of three different soil treatments. Paracytic type of stomata is present in all three leaves. Anatomical properties of plant parts are sources for taxonomic inferences in different groups of flowering plants.

The aim of present study is to use stomatal characters as aid in taxonomy of medicinally useful Cassia plants. The study would help in the identification and authentication of these medicinal plants on the basis of stomatogenesis.

 

Stomata in Rice

Physiology of Cell Membranes, Stomata And Photosynthetic Pigments of Rice (Oryza sativa L.) Under High Temperature

by Saleh H., Thind  S. K.  (2015)

in The Global Journals: Volume : 4 | Issue : 6 | June 2015 • ISSN No 2277 – 8179

Twenty genotypes of rice were evaluated for their physiological tolerance of cellular membranes, stomata and photosynthetic pigments under high temperature stress. The selected genotypes were grown at two sowing dates viz; normal and stress environment. High temperature negatively affected these parameters and genotypic variation was observed. Photosynthetic pigments were significantly reduced under stress, while the number of stomata increased.

Membrane thermal stability (MTS) decreased with increasing temperature exposure; hence 30oC recorded highest while 55oC recorded lowest MTS. Genotype Ganjay had highest chlorophyll a with lowest number of stomata in lower epidermis under stress. The highest MTS values were recorded for genotypes PR121, IR6 and PR122. These four genotypes can be recommended for growing under high temperature stress.

Read the full article: The Global Journals

Transmembrane ion fluxes and stomatal closure

 

The role of plasma membrane H⁺-ATPase in jasmonate-induced ion fluxes and stomatal closure in Arabidopsis thaliana

by Yan S., McLamore E.S., Dong S., Gao H., Taguchi M., Wang N., Zhang T., Su X., Shen Y. (2015)

in The Plant Journal – Accepted Article

Abstract

Methyl jasmonate (MeJA) elicits stomatal closure in many plant species. Stomatal closure is accompanied by large ion fluxes across the plasma membrane (PM). Here, we recorded the transmembrane ion fluxes of H⁺, Ca²⁺ and K⁺ in guard cells of wild type (Col-0), the CORONATINE INSENSITIVE1 (COI1) mutant coi1-1, and the PM H⁺-ATPase mutants aha1-6 and aha1-7, using a non-invasive micro-test technique. We showed that MeJA induced transmembrane H⁺ efflux, Ca²⁺ influx and K⁺ efflux across the PM of Col-0 guard cells. However, this ion transport was abolished in coi1-1 guard cells, suggesting that MeJA-induced transmembrane ion flux requires COI1. Furthermore, the H⁺ efflux and Ca²⁺ influx in Col-0 guard cells was impaired by vanadate pretreatment or PM H⁺-ATPase mutation, suggested that the rapid H⁺ efflux mediated by PM H⁺-ATPases could function upstream of the Ca²⁺ flux. After the rapid H⁺ efflux, the Col-0 guard cells had a longer oscillation period than before MeJA treatment, indicating that the activity of the PM H⁺-ATPase was reduced. Finally, the elevation of cytosolic Ca²⁺ concentration and the depolarized PM drive the efflux of K⁺ from the cell, resulting in loss of turgor and closure of the stomate.

See the text: Wiley Online Library

 

The role of guard-cell photosynthesis in stomatal conductance responses

 

Guard cell photosynthesis is critical for stomatal turgor production, yet does not directly mediate CO₂– and ABA-induced stomatal closing

by Azoulay-Shemer T., Palomares A., Bagheri A., Israelsson-Nordstrom M., Engineer C. B., Bargmann B. O.R., Stephan A. B., Schroeder J. I.  (2015)

in The Plant Journal – Accepted Article

Summary

Stomata mediate gas exchange between the inter-cellular spaces of leaves and the atmosphere. CO₂ levels in leaves (Ci) are determined by respiration, photosynthesis, stomatal conductance and atmospheric [CO₂]. [CO₂] in leaves mediates stomatal movements. The role of guard-cell photosynthesis in stomatal conductance responses is a matter of debate, and genetic approaches are needed. We have generated transgenic Arabidopsis plants that are chlorophyll-deficient in guard cells only, expressing a constitutively active chlorophyllase in a guard-cell specific enhancer trap-line. Our data show that more than 90% of guard cells were chlorophyll-deficient. Interestingly, approximately ~ 45% of stomata had an unusual, previously not-described, morphology of thin-shaped chlorophyll-less stomata. Nevertheless, stomatal size, stomatal index, plant morphology, and whole-leaf photosynthetic parameters (PSII, qP, qN, FV’/FM’) were comparable to wild-type plants. Time-resolved intact leaf gas exchange analyses showed a reduction in stomatal conductance and carbon assimilation rates of the transgenic plants. Normalization of CO₂ responses showed that stomata of transgenic plants respond to [CO₂] shifts. Detailed stomatal aperture measurements of normal kidney-shaped stomata, which lack chlorophyll, showed stomatal closing responses to [CO₂] elevation and abscisic acid (ABA), while thin-shaped stomata were continuously closed. Our present findings show that stomatal movement responses to [CO₂] and ABA are functional in guard cells that lack chlorophyll. These data suggest that guard-cell CO₂ and ABA signal transduction are not directly modulated by guard-cell photosynthesis/electron transport. Moreover, the finding that chlorophyll-less stomata cause a “deflated” thin-shaped phenotype, suggests that photosynthesis in guard cells is critical for energization and guard-cell turgor production.

See the text: Wiley Online Library

 

Stomatal behavior relative to embolism resistance

Responses of two semiarid conifer tree species to reduced precipitation and warming reveal new perspectives for stomatal regulation

by GARCIA-FORNER N., ADAMS H. D., SEVANTO S., COLLINS A. D., DICKMAN L. T. , HUDSON P. J., ZEPPEL M., MARTÍNEZ-VILALTA J., MCDOWELL N.G. (2015)

in Plant, Cell & Environment : Accepted Article

Abstract

Relatively anisohydric species are predicted to be more predisposed to hydraulic failure than relatively isohydric species, as they operate with narrower hydraulic safety margins. We subjected co-occurring anisohydric Juniperus monosperma and isohydric Pinus edulis trees to warming, reduced precipitation, or both, and measured their gas exchange and hydraulic responses. We found that reductions in stomatal conductance and assimilation by heat and drought were more frequent during relatively moist periods, but these effects were not exacerbated in the combined heat and drought treatment. Counter to expectations, both species exhibited similar g_s temporal dynamics in response to drought. Further, whereas P. edulis exhibited chronic embolism, J. monosperma showed very little embolism due to its conservative stomatal regulation and maintenance of xylem water potential above the embolism entry point. This tight stomatal control and low levels of embolism experienced by juniper refuted the notion that very low water potentials during drought are associated with loose stomatal control and with the hypothesis that anisohydric species are more prone to hydraulic failure than isohydric species. Because direct association of stomatal behavior with embolism resistance can be misleading, we advocate consideration of stomatal behavior relative to embolism resistance for classifying species drought response strategies.

See the text: Wiley Online Library