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Revista Cubana de Ciencias Forestales

On-line version ISSN 2310-3469

Rev cubana ciencias forestales vol.8 no.1 Pinar del Río Jan.-Apr. 2020  Epub Apr 09, 2020


Original article

Characterization of stomata in the species Juglans jamaicensis ssp. insularis (Griseb.) H. Schaarschm.( walnut tree)

Caridad Rivera Calvo1  *

Claudia María Pérez Reyes1

Irmina Armas Armas1

Armando Pérez Tamargo1

1Universidad de Pinar del Río "Hermanos Saíz Montes de Oca", Facultad de Ciencias Forestales y Agropecuarias. Pinar del Río, Cuba.


Juglans jamaicensis subsp insularis, is an endemism of Pinar del Río, protected by Resolution 330/1999 of the Ministry of Agriculture included in the Red List of Cuban Vascular Flora. It is a species that has been little studied in its physiology and anatomy. The present study aims to characterize the stomas of Juglans jamaicensis subsp. insularis. Epidermal impressions were made with nail polish on both sides of the leaflets. These were observed with a novel optical microscope (NLCD-307 B). The length and width of the stomas were measured with a 40x lens, the density per unit area (cm²) and the stomatic index. The average size of the stomas is 16.5 μm wide and 19.9 μm long. The stomas were considered small, with a high density and a stomatic index of 15.82.

Keywords: Stomatic index; stomatic density; stomata size.


The gender Juglans, groups the plants of the family Juglandaceae known as walnut trees. About 50 species have been reported from China, Japan, India, Persia, and much of the Americas (Acevedo et al., 2012). There are 12 species in that area, two in the West Indies and several in South America (León and Alain, 1951). There are also isolated individuals with an even wider distribution in semi-deciduous tropical forests (López, 2000).

Juglans jamaicensis subsp. insularis, is an endemism of Pinar del Río. Its distribution is restricted to the regions of Sierra del Rosario and the base of the mogotes of Sierra de los Órganos, grows in an isolated way, never reaching the top, preferring clayey soils between the plains and near the rivers. In forests at the base of mogotes it grows on a substrate of humic yields from shady places and serpentine. It is reported in Minas de Matahambre (Sumidero), Viñales (San Vicente, Hoyo del Ruiseñor), La Palma: (San Andrés de Caiguanabo), Los Palacios (San Diego de los Baños) and Bahía Honda (Urquiola et al., 2010).

This species has been classified as Critically Endangered (González-Torres et al., 2016), due to the loss and degradation of habitat by agricultural activity, livestock and the effect of exotic plants and animals, and is protected by Resolution 330/1999 of the Ministry of Agriculture. Gaceta oficial de la república de Cuba (1999)

The effects of climate change on flora in general, and on threatened flora in particular, force us to study the morphoanatomy of species in order to understand how they evolve and adapt. Currently, the water deficit, increased by the possible consequences of climate change, is considered the main environmental factor limiting the growth and productivity of plantations (Silva et al., 2017).

The morphological and physiological mechanisms involved in the processes of adaptation-acclimatisation to stress operate at different levels of the plant, with the aim of ensuring water functionality in the new environmental conditions, the stomas being vital for the homeostasis of the plant (Torala et al., 2010). Because they are responsible for the exchange of gases between the atmosphere and the leaf and thus prevent excessive water loss, hence the importance of knowing the number, shape and factors that control their opening or closing (Vázquez y Torres, 2007).

Therefore, it is necessary to know the anatomy and characteristics of stomas as entities in charge of gas exchange and transpiration and the response to adjustments in them, as a result of changes in environmental conditions. Therefore, the aim of the study was to characterize the stomas of the species Juglans jamaicensis subsp. insularis.

Materials and methods

The plant material used was leaves from individuals of Juglans jamaicensis ssp insularis collected in San Andrés de Caiguanabo, La Palma Municipality, Pinar del Río Province. To characterize the stomas, epidermal impressions were made on both sides of the leaflets, using nail polish, to a total of 20 samples, taken at random. They were observed with a Novel brand optical microscope, model NLCD-307 B and measured in length and width, with an ocular micrometer calibrated for the 40x lens.

The stoma count was performed to determine the density per unit area (mm²) and to calculate the stoma index according to (Reyes et al., 2015) (Equation 1).



= Stomatic Index


= Number of stomas per field of view


= Number of epidermal cells in the field of view

The length and width of the stomas were measured and classified by size according to Bory et al., (2008).

Results and discussion

Stoma size

The number of stomas on the adaxial (beam) surface compared to the abaxial (back) surface is a distinguishing feature of different species. Plants with bundle stomas are called epistomata, typical of aquatic plants (Reyes et al., 2015), if they are present only on the underside, hypestomata, from mesophytic habitats and those with bundle and underside stomas, ampistomata, common from arid environments (Bieto and Talón, 2008; Reyes et al., 2015). The hypostomatic Juglansjamaicensises leaf (Figure 1) (Rivera et al., 2018), this typical character in many dicotyledons is considered a feature of primitivism Camargo, (2009).

The average stomach width was 16.5μm and the average length was 19.9μm. According to Bory et al., (2008) these stomas are small. Stoma size is a key factor in the process of acclimatization to water stress, as there is an inverse relationship between this character and drought resistance (Toral et al., 2010).

The species J. jamaisensis ssp.insularis lives mainly in the base and holes of hummocks, where water easily infiltrates through the yields developing then the edaphic drought, therefore, the reduction of the stomach size is considered an adaptation to these conditions.

The increase in the number of small stomas, together with the presence of glandular hairs and trichomes with no apparent secretory function, are catalogued as features of xeromorphism (Ely et al., 2005). This characteristic of the presence of glandular hairs present in the species is associated with the function of accumulating water that is deposited on the epidermis (Rivera et al., 2018) .

Wu et al., (2018) found that two subtropical forest tree species, Schima superbay Syzygium rehderianumse, show adjustments in anatomy and stoma size at different temperatures and water stress. For Schima superbaen increased temperature led to a reduction in stoma density, while in Syzygium rehderianumse reduced stoma size.

Source: Photos of the author

Fig. 1 - Adaxial epidermal impression (A) and abaxial epidermal impression of the sheet (B) (640x)  

Stomatic index and density

The average stoma count was 22 per field and 117 epidermal cells. By determining stoma density in the leaves, 440 stomas/mm² were obtained. For other species it has been reported that the number of stomas per leaf area (density or stomatal frequency) is recorded between 10 and 2000 per mm² (Naizaque et al., 2014) and indicates for Accasellowiana, a shrub species of Myrtaceae, stomatal density values of 91/mm2 to 78/mm2 depending on the plant strata. Although studies on stomatic density are limited in tree species, it could be considered that, in the species, the stomatic density is high (Figure 2).

The average stomach index calculated was 15.82, which coincides with those calculated in Annona muricata L. and Annona montana MADFAC (Parés et al., 2004) .

Kivimäenpää et al., (2017) relate high stomatic density to the mesophilic formed by several layers of chlorophyll parenchyma in deciduous species with sunny habitats, which guarantees photosynthetic efficiency.

Source: Author's photos.

Fig. 2 - Distribution of stomas on the abaxial side of the leaf (160x) 

The stomas of the species Juglans jamaicensis ssp.insularis are small and occur in a high density per field with a stomach index of 15.82.

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Received: January 08, 2020; Accepted: February 24, 2020

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