Nectary stomata in Bignoniaceae

Nuptial nectary structure of Bignoniaceae from Argentina

by Rivera G. L. (2000)

In Darwiniana 38(3-4): 227-239 – License: CC BY-NC 4.0 –


Nuptial nectary characteristics were investigated in 37 taxa of Bignoniaceae.

A nuptial nectary associated to the floral axis was found in all species. Two main types can be distinguished according to their degree of development and functionality:

1) vestigial and non-secretory and

2) well-developed and secretory.

The former is characteristic of Clytostoma spp., while the latter is found in the remaining species. Two subvarieties of the secretory type of nectary can be discerned according to their position and shape:

1) annular, found in Adenocalymma, Amphilophium, Anemopaegma, Arrabidaea,Dolichandra, Eccremocarpus, Macfadyena, Melloa, Pithecoctenium, Tabebuia, and Tecoma, and

2) cylindrical, found in Argylia, Cuspidaria, Jacaranda, Mansoa, Parabignonia, Pyrostegia, and Tynnanthus.

Anatomically, two tissues are distinguished:

1) a single-layered epidermis covered by a cuticle and a variable number of stomata, and

2) a secretory tissue composed of compactly arranged parenchyma cells.

Both nectary size and nectary/ovary ratio were usually larger in lianas (Bignonieae) than in trees (Tecomeae). Nectary type proved to be consistent among species of same genus but not among genera of same tribe. Nectary features such as vascularization, presence of trichomes and nectary type were constant within the analyzed species and therefore have a reliable taxonomic value.



Stomatal conductance and transpiration

Stomatal conductance and transpiration of co-occurring seedlings with varying shade tolerance

by Siegert C. M., Levia D. F. (2011)

  • Courtney M. Siegert,
  • Delphis F. Levia,
  1. Department of Geography, University of Delaware, Newark, USA
  2. Departments of Geography and Plant and Soil Sciences, University of Delaware, Newark, USA


In Trees 25: 1091–1102 – –


Forest ecosystems exert a large influence on the hydrologic cycle through transpiration, with the majority supplied by saplings and adult trees. However, a measurable amount is also supplied by seedlings. The contribution of seedlings is dependent upon species, which is ultimately controlled by microclimate.

The objectives of this study were to

(1) observe meteorological conditions of two forest microclimates; and

(2) assess the intra- and interspecific stomatal conductance and transpiration responses of naturally occurring seedlings of varying shade tolerance.

Naturally established seedlings in a deciduous forest understory and an adjacent clearing were monitored throughout the 2008 growing season in southeastern Pennsylvania (39°49′N, 75°43′W). The understory microclimate conditions overall had a lower degree of variability and had consistently lower mean quantum flux densities, air temperature, vapor pressure deficit, volumetric water content, and soil temperature than the clearing plot.

Understory seedlings of Fagus grandifolia Ehrh. (American beech) and Prunus serotina L. (black cherry) had significantly lower mean monthly rates of water loss (p = 0.05) than clearing seedlings [P. serotina and Liriodendron tulipifera L. (yellow poplar)]. Additionally, water loss by shade-grown P. serotina seedlings was significantly lower (p = 0.05) than by sun-grown seedlings.

Physiological differences, specifically shade tolerance, played an important role in determining the rates of stomatal conductance and transpiration in the seedlings. To a lesser degree, microclimate variability also influenced water loss.

The results of this study validate results obtained in previous studies conducted largely under controlled conditions. Field validations are critical to developing better models and forest management strategies.

New stomatal flux-based critical levels CLef for forest protection against visible O3 injury

An epidemiological assessment of stomatal ozone flux-based critical levels for visible ozone injury in Southern European forests

by Sicard P., De Marco A., Dalstein-Richier L., Tagliaferro F., Renou C., Paoletti E. (2016)

Pierre Sicard, a, Alessandra De Marco, b, Laurence Dalstein-Richier, c, Francesco Tagliaferro, d, Camille Renou, a, Elena Paoletti, e

ACRI-HE, 260 route du Pin Montard, BP 234, 06904 Sophia Antipolis cedex, France

ENEA (Italian National Agency for New Technologies, Energy and Sustainable Economic Development), 76, Lungotevere Thaon de Revel, Rome, Italy

GIEFS (Groupe International d’Etudes des Forêts Sud-européennes), 60, Avenue des Hespérides, 06300 Nice, France

IPLA (Istituto per le Piante da Legno e l‘Ambiente), Corso Casale 476, 10132 Turin, Italy

eIPSP-CNR (Consiglio Nazionale delle Ricerche — Istituto per la Protezione Sostenibile delle Piante), Via Madonna del Piano 10, 50019 Sesto Fiorentino (Florence), Italy


In Sci. Total Environ. 541: 729–741 – ttps:// –



We develop new flux-based critical levels CLef for forest protection against visible O3 injury.•

We recommend the use of POD0 calculated for hours with a non-null global radiation.•

We propose CLef = 19 & 32 mmol m− 2 for high & moderate O3 sensitive conifers respectively.•

We propose CLef = 19 & 25 mmol m− 2 for high & moderate O3 sensitive broadleaves respectively.


Southern forests are at the highest ozone (O3) risk in Europe where ground-level O3 is a pressing sanitary problem for ecosystem health. Exposure-based standards for protecting vegetation are not representative of actual field conditions.

A biologically-sound stomatal flux-based standard has been proposed, although critical levels for protection still need to be validated. This innovative epidemiological assessment of forest responses to O3 was carried out in 54 plots in Southeastern France and Northwestern Italy in 2012 and 2013.

Three O3 indices, namely the accumulated exposure AOT40, and the accumulated stomatal flux with and without an hourly threshold of uptake (POD1 and POD0) were compared. Stomatal O3 fluxes were modeled (DO3SE) and correlated to measured forest-response indicators, i.e. crown defoliation, crown discoloration and visible foliar O3 injury. Soil water content, a key variable affecting the severity of visible foliar O3 injury, was included in DO3SE.

Based on flux–effect relationships, we developed species-specific flux-based critical levels (CLef) for forest protection against visible O3 injury. For O3 sensitive conifers, CLef of 19 mmol m− 2 for Pinus cembra (high O3 sensitivity) and 32 mmol m− 2 for Pinus halepensis (moderate O3 sensitivity) were calculated. For broadleaved species, we obtained a CLef of 25 mmol m− 2 for Fagus sylvatica (moderate O3 sensitivity) and of 19 mmol m− 2 for Fraxinus excelsior (high O3 sensitivity). We showed that an assessment based on PODY and on real plant symptoms is more appropriated than the concentration-based method. Indeed, POD0 was better correlated with visible foliar O3 injury than AOT40, whereas AOT40 was better correlated with crown discoloration and defoliation (aspecific indicators).

To avoid an underestimation of the real O3 uptake, we recommend the use of POD0 calculated for hours with a non-null global radiation over the 24-h O3 accumulation window.

Verapamil inhibits blue light signaling in stomata without inhibiting the pump

Inhibition of the stomatal blue light response by verapamil at high concentration

by Shimazaki K.-i., Tominaga M., Shigenaga A. (1997)

Department of Biology, Faculty of Science, Kyushu University, Fukuoka, Japan.


In Plant Cell Physiol. 38: 747–750 –


Blue light-dependent proton pumping in guard cell protoplasts and light-induced stomatal opening in the epidermis were inhibited by 1 mM verapamil, a Ca2+ channel blocker.

Proton pumping and stomatal opening induced by fusicoccin, an activator of plasma membrane proton pump, were not inhibited by verapamil.

These results suggest that verapamil inhibits blue light signaling in guard cells without inhibiting the pump.

Photosynthetic properties of stomatal protoplasts

Photosynthetic properties of guard cell protoplasts from Vicia faba

by Shimazaki K., Gotow K., Kondo N. (1982)

Ken-ichiro Shimazaki, Kiyoshi Gotow, Noriaki Kondo,

1Division of Environmental Biology, National Institute for Environmental Studies Yatabe, Ibaraki 305, Japan


In Plant Cell Physiol. 23: 871-879 –


Guard cell protoplasts were isolated enzymatically from the epidermis of Vicia faba L. and their photosynthetic activities were investigated. Time courses of light-induced changes in the chlorophyll a fluorescence intensity of these protoplasts showed essentially the same induction kinetics as found for mesophyll protoplasts of Vicia.

The transient change in the fluorescence intensity was affected by DCMU, an inhibitor of photosystem II; by phenylmercuric acetate, an inhibitor of ferredoxin and ferredoxin NADP reductase; and by methyl viologen, an acceptor of photosystem I. Low temperature (77 K) emission spectra of the protoplasts had peaks at 684 and 735 nm and a shoulder near 695 nm.

A high O2 uptake (175 μmol mg−1 Chl hr−1) was observed in guard cell protoplasts kept in darkness, which was inhibited by 2 mM KCN or NaN3 by about 60%.

On illumination, this O2 uptake was partially or completely suppressed, but its suppression was removed by DCMU, which indicates that oxygen was evolved (150 μmol mg−1 Chl hr−1) photosynthetically.

We concluded that both photosystems I and II function in guard cell chloroplasts and that these protoplasts have high respiratory activity.

Stomatal aperture and the sensing of the environment

Stomatal aperture and the sensing of the environment by guard cells

Sheriff D. W. (1979)

D. W. Sheriff

The Australian National University, Canberra, Australia


In Plant Cell Environ. 2: 15–22 – –


Carbon dioxide fixation in stomata

The physiology of stomata. I. Carbon dioxide fixation in guard cells

by Shaw M., MacLachlan G. A. (1954)

Michael Shaw, G. A. Maclachlan,


In Can J Bot 32: 784-794 – –


The guard cells of Tulipa gesneriana L. were found to contain both chlorophylls a and b. The total chlorophyll content was estimated to be of the order of 0.5 × 10−12 gm, per cell.

By exposure to radioactive carbon dioxide followed by microautoradiography, selective carbon dioxide uptake in the light was demonstrated in the stomatal cells of AlliumHordeumNicotianaSedumTradescantiaTulipa, and Vicia,

A less intense uptake was observed in darkness with AlliumSedumTulipa, and Vicia. The rate of guard-cell photosynthesis was estimated to be of the order of 0.02 × 10−12 M. carbon dioxide per cell per hour at 500 ft-c. and in 0.04% (v/v) carbon dioxide.

It was concluded that this rate was too low to account for the increase in osmotic potential caused by illumination.