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|Vol. 11(3), pp. 11-16||The McAllen International Orchid Society Journal||March 2010|
Effective Publication Date : 23-Mar-2010
Universidad Autónoma de Nuevo León
Facultad de Ciencias Biológicas
Laboratorio de Manejo de Vida Silvestre
(translated by Eric Olsen)
This paper reports the development of abnormal inflorescences in two Mesadenus polyanthus (Orchidaceae) plants from two distinct municipalities on the state of Nuevo León, Mexico. They were observed under domestic conditions along with others of the same species. Each plant was in a container, under a Flamboyant tree (Delonix regia), exposed to the weather. The causes are attributed to stress from the change in habitat. Currently both plants flower normally.
The plants are grown in individual containers, under a tree that provides them with shade (approximately 90%) during the hottest hours of the day (between 10:00 a.m. and 3:00 p.m.), on the patio of the author. They are always there, whatever the weather, since it has been observed that said species grows in both humid environments as well as semi-arid ones.
Fig. 1. Appearance of the ravine in the Cerro de La Silla, Municipality of Guadalupe and view of the habitat of the plant obtained there.
On the sixth rise of the Cerro de La Silla (Saddle Hill), approaching from the Colonia Rincón de la Sierra, in the Municipality of Guadalupe, Nuevo León, Mexico, we encountered on the 21st of June 2003 various plants growing on a large rock located approximately at 378050 E and 2834778 N, at an elevation of 920 meters above mean sea level. The place is in a ravine on the eastern side (NE) of the mountain chain to which the previously mentioned hill belongs. Compared to the western side (SW) which is dry and covered predominantly with a spiny scrub, the ravine is humid and forested (Fig. 1).
Fig. 2. Sample obtained of M. polyanthus shown in situ, in the Cerro de La Silla, Guadalupe.
The eastern side is dominated by live oaks (Quercus), although there are also wild walnuts (Juglans) and other trees (Platanus, Arbutus). There are also spiny shrubs which range from presence to abundance as the altitude increases. Since the plants appeared little different from the ones of M. polyanthus that we already had and were the first in the area to seem to us to be orchids, we took some (Fig. 2) to cultivate at home and see how they flowered (there were no inflorescences at this point).
Fig. 3. Stages of growth of M. polyanthus from the Cerro de La Silla, Guadalupe, N.L., in 2004.
Fig. 4. Stages of flowering of M. polyanthus from the Cerro de La Silla, Guadalupe, during 2005 (A), 2006 (B and C) and 2009 (D).
Flowerings. In January 2004 an infloresence began to grow (Fig. 3-A) on the plants. It developed very slowly. In September it looked like a spider emerging from among the leaves (Fig. 3-B); in October more showed (Fig. 3-C); in December the flowers appeared to have dried (Fig. 3-D); in March 2005 the inflorescence was totally dry (Fig. 4-A). At the end of 2005 and beginning of 2006 two inflorescences began to develop at the normal time (Fig. 4-B); however, one did not finish developing and did not display flowers. The other one did grow, but suddenly it stopped when several centimeters long; in June, this inflorescence had what appeared to be leaves (Fig. 4-C) -- they were the enlarged and swollen bracts, like small leaves. In 2007 and 2008 it did not flower. During 2009 the whole cycle was normal (Fig. 4-D). In 2010 there are currently two developing inflorescences which will apparently be normal.
Fig. 5. One of the live oaks in Mojarras Canyon, in the Sierra Picachos, Municipality of Dr. González.
Fig. 6. Sample of M. polyanthus obtained, shown in situ, in the Sierra Picachos, in Mojarras Canyon, Dr. González.
The second plant that displayed the same malformation was originally obtained on February 19th 2005, in the Sierra Picachos, in the Mojarras Canyon, Municipality of Dr. González, Nuevo León, Mexico. A low ridge and a large, elongated mound of rocks formed a passage like a small canyon (apporximately at 425171 E and 2873087 N, with an altitude of 403 meters above mean sea level). The area vegetation consisted of spiny shrubs and a few live oaks (Quercus). In contrast, in the passage there were only live oaks (Fig. 5), which indicates that it is more humid than the ridges that form it. It is so humid and protected from the wind that the plants of M. polyanthus frequently still have their leaves when flowering, something that has so far not been seen in all of the other sites where this species of plant has been found. At the site there were various plants growing on the passage's rock walls and some located in the passage center. One with flowers was sampled (Fig. 6).
Fig. 7. Flowering stages in M. polyanthus from the Sierra Picachos (Dr. González) during 2006 (A), 2007 (B), 2009 (C) and 2010 (D).
Flowerings. In 2005 the flowers of this plant were normal, as can be seen in Fig. 6. In 2006 the flowers did not open at the normal time and in June looked like the sample from the first case (Fig. 7-A), with the inflorescence beginning to dry out in July. In 2007 the malformation was repeated; in July the tip of the inflorescence had what looked like small leaves. In 2008 it did not flower. In 2009 and 2010 in flowered normally (Fig. 7-C) (Fig. 7-D), only this time, there were two inflorescences due to the fact that it was now two independent plants.
Possible Causes. Various samples of different species have been obtained from several municipalities in the state of Nuevo León. In the particular case of M. polyanthus, this was done in order to see how they flowered since plants with different leaves (abundant or few) had been found and it was suspected that they could be distinct species. Among the plants of this species only two of them showed the malformations, which being temporary, could be due to the stress produced by the climatic change. After all, growing away from their natural habitat but conserving the soil where they grew, the conditions of temperature and humidity were different from those normal in their habitats. Perhaps these two plants had some sort of deficiency or were more susceptible. Finally, the plant began to flower normally in both season and appearance, when the causes of stress were overcome; that is to say, when they had adapted to the new conditions.
One important recommendation where abnormal developments occur is that the structure(s) should be saved. Due to the inexperience of the author, this was not done and only photos from the second case are available. This hinders doing a close examination of the causes and effects.