Esporogénesis y esporas de <i>Equisetum bogotense</i> (Equisetaceae) de las áreas montañosas de Colombia

• DOI: 10.15517/rbt.v61i3.11786
• Publication Date: 2014-07-29T22:48:06Z
• Authors: Edgar Javier Rinc...; Gerardo Andrés To...; Cristina Hilda Ro...
• Keywords: sporoderm ultrastructure; 570; spores; Vegetales; QH301-705.5; Equisetum; Ethnobotany; orbicules; Colombia; orbículas; Equisetum bogotense H.B.K; Plantas; ultraestructura del esporodermo; Strobilus; Agricultural and Biological Sciences; Humanities; Evolutionary Innovations and Conservation of Cycads; Stamen; Exosporio; Ciencias Naturales; Biology (General); Tapetum; Biology; Ecology, Evolution, Behavior and Systematics; Esporogénesis; Botánica; perispore; Botany; Life Sciences; Spore; esporogénesis; FOS: Humanities; esporas; http://aims.fao.org/aos/agrovoc/c_35542; exospore; Esporas; exosporio; Equisetum bogotense H.B.K.; perisporio; Pollen; sporogenesis; Microspore; Art

Studies on some reproductive traits in Equisetum species are scarce and valuable to understand species distribution. Therefore, a detailed study of the sporogenesis process and spore development in E. bogotense is presented, with an analysis of the main events during meiosis, maturation of spores, spore wall ultrastructure, orbicules and elaters. Specimens were collected from 500 to 4500 m in Cauca, Colombia. Strobili at different maturation stages were fixed, dehydrated, embedded in resin, and ultra-microtome obtained sections were stained with Toluidine blue. Observations were made with optical microscopy with differential interference contrast illumination technique (DIC), transmission and scanning electron microscopy (TEM and SEM). Ultrathin sections (70-80 microm) for TEM observations were stained with uranyl acetate and lead citrate; while samples for SEM observations, were fixed, dehydrated in 2.2-dimethoxypropane and dried at critical point as in standard methods. Strobili have numerous mature sporangiophores, each one with a peltate structure, the scutellum, bearing five-six sessile sporangia attached to the axis of strobilus by the manubrium. Immature sporocytes (spore mother cells) are tightly packed within the young sporangia. The sporocytes quickly undergo meiosis, by passing the stage of archesporium and give origin to tetrads of spores. The tapetum loses histological integrity during early stages of sporogenesis, intrudes as a plasmodial mass into the cavity of the sporangium, partially surrounding premeiotic sporocytes, and then, tetrads and adult spores. The tapetum disintegrates towards the end of the sporogenesis, leaving spores free within the sporangial cavity. Spores present several cytological changes that allow them to achieve greater size and increase the number of plastids, before reaching the adult stage. Sporoderm includes three layers external to the cytoplasmic membrane of the spore cell, and they are pseudoendospore, exospore and perispore. Viewed with SEM, the exospore is smooth to rugulate, with micro perforations, while the perispore is muriform, rugate, with narrow, delicate, discontinuous, randomly distributed folds delimiting incomplete, irregular areolae, externally covered by of different size, densely distributed orbicules. These orbicules are also found all over the external face and margins of the elaters, while the internal face is smooth and lack orbicules. Viewed with TEM, the exospore is a thick layer of fine granular material, while perispore is a thinner layer of dense, separate orbicules. The elaters are composed by two layers of fibrillar material: an inner layer with longitudinally oriented fibrils and an outer, thicker and less dense layer with fibrils transversely fibrils and abundant, external orbicules. It is suggested that the processes of ontogeny and characters of the sporoderm are relatively constant in Equisetum; however, sporogenesis in E. bogotense is synchronous and this condition has been observed so far only in E. giganteum, a tropical genus also found in Colombia.<br/>الدراسات حول بعض الصفات الإنجابية في أنواع الخيول نادرة وقيمة لفهم توزيع الأنواع. لذلك، يتم تقديم دراسة مفصلة لعملية تكوين الأبواغ وتطور الأبواغ في E. bogotense، مع تحليل للأحداث الرئيسية أثناء الانقسام الاختزالي، ونضج الأبواغ، والبنية التحتية لجدار الأبواغ، والدوارات و elaters. تم جمع العينات من 500 إلى 4500 متر في كاوكا، كولومبيا. تم تثبيت Strobili في مراحل النضج المختلفة، وتجفيفها، وتضمينها في الراتنج، وتم تلطيخ المقاطع التي تم الحصول عليها فائقة الصغر بأزرق التولويدين. تم إجراء الملاحظات باستخدام المجهر البصري مع تقنية إضاءة تباين التداخل التفاضلي (DIC)، والإرسال والمسح المجهري الإلكتروني (TEM و SEM). تم تلطيخ المقاطع فائقة النحافة (70-80 ميكرومتر) لملاحظات TEM بأسيتات اليورانيل وسترات الرصاص ؛ بينما تم تثبيت عينات ملاحظات SEM وتجفيفها في 2.2 - dimethoxypropane وتجفيفها عند نقطة حرجة كما هو الحال في الطرق القياسية. Strobili لديها العديد من sporangiophores الناضجة، كل واحد مع بنية peltate، و scutellum، تحمل خمسة ستة sporangia لا طائشة تعلق على محور strobilus بواسطة مانوبريوم. يتم تعبئة الخلايا البوغية غير الناضجة (الخلايا الأم البوغية) بإحكام داخل الأبواغ الصغيرة. تخضع الخلايا البوغية بسرعة للانقسام الاختزالي، عن طريق اجتياز مرحلة الأبواغ القوسية وإعطاء الأصل لرباعيات الجراثيم. يفقد البساط سلامته النسيجية خلال المراحل المبكرة من تكوين الأبواغ، ويتدخل ككتلة بلازمية في تجويف الأبواغ، ويحيط جزئيًا بالخلايا البوغية قبل الانتباذ، ثم الرباعيات والأبواغ البالغة. يتفكك البساط نحو نهاية تكوين الأبواغ، تاركًا الأبواغ حرة داخل التجويف الأبواغي. تُظهر الجراثيم العديد من التغيرات الخلوية التي تسمح لها بتحقيق حجم أكبر وزيادة عدد البلاستيدات، قبل الوصول إلى مرحلة البلوغ. يشمل الأديم البوغي ثلاث طبقات خارج الغشاء السيتوبلازمي للخلية البوغية، وهي بوغ داخلي كاذب وبوغ خارجي وبوغ دائري. عند النظر إليه باستخدام SEM، يكون البوغ الخارجي سلسًا في التجعد، مع ثقوب دقيقة، في حين أن البوغ المحيطي حجري الشكل، متجعد، مع طيات ضيقة وحساسة ومتقطعة وموزعة عشوائيًا تحدد الهالات غير المكتملة وغير المنتظمة، مغطاة خارجيًا بأحجام مختلفة، ودوارات موزعة بكثافة. توجد هذه الدوارات أيضًا في جميع أنحاء الوجه الخارجي وهوامش الإيلاتر، في حين أن الوجه الداخلي أملس ويفتقر إلى الدوارات. عند النظر إليه باستخدام TEM، فإن البوغ الخارجي عبارة عن طبقة سميكة من المواد الحبيبية الدقيقة، في حين أن البوغ الخارجي عبارة عن طبقة أرق من الحبيبات الكثيفة المنفصلة. تتكون الإيلاترات من طبقتين من مادة اللييفات: طبقة داخلية ذات لييفات موجهة طوليًا وطبقة خارجية أكثر سمكًا وأقل كثافة مع لييفات مستعرضة ودوائر خارجية وفيرة. يُقترح أن تكون عمليات تكوين الجنين وشخصيات الأدمة البوغية ثابتة نسبيًا في Equisetum ؛ ومع ذلك، فإن تكوين الأبواغ في E. bogotense متزامن وقد لوحظت هذه الحالة حتى الآن فقط في E. giganteum، وهو جنس استوائي موجود أيضًا في كولومبيا.<br/>Etudes on some reproductive traits in Equisetum species are scarce and valuable to understand species distribution. Therefore, a detailed study of the sporogenesis process and spore development in E. bogotense is presented, with an analysis of the main events during meiosis, maturation of spores, spore wall ultrastructure, orbicules and elaters. Specimens were collected from 500 to 4500 m in Cauca, Colombia. Strobili at different maturation stages were fixed, dehydrated, embedded in resin, and ultra-microtome obtained sections were stained with Toluidine blue. Observations were made with optical microscopy with differential interference contrast illumination technique (DIC), transmission and scanning electron microscopy (TEM and SEM). Ultrathin sections (70-80 microm) for TEM observations were stained with uranyl acetate and lead citrate ; while samples for SEM observations, were fixed, dehydrated in 2.2-dimethoxypropane and dried at critical point as in standard methods. Strobili have numerous mature sporangiophores, each one with a peltate structure, the scutellum, bearing five-six sessile sporangia attached to the axis of strobilus by the manubrium. Imature sporocytes (spore mother cells) are tightly packed within the young sporangia. The sporocytes quickly undergo meiosis, by passing the stage of archesporium and give origin to tetrads of spores. The tapetum loses histological integrity during early stages of sporogenesis, intrudes as a plasmodial mass into the cavity of the sporangium, partially surrounding premeiotic sporocytes, and then, tetrads and adult spores. The tapetum disintegrates towards the end of the sporogenesis, leaving spores free within the sporangial cavity. Spores present several cytological changes that allow them to achieve greater size and increase the number of plastids, before reaching the adult stage. Sporoderm includes three layers external to the cytoplasmic membrane of the spore cell, and they are pseudoendospore, exospore and perispore. Viewed with SEM, the exospore is smooth to rugulate, with micro perforations, while the perispore is muriform, rugate, with narrow, délicate, discontinuous, randomly distributed folds delimiting incomplete, irregular aréolee, externally covered by of different size, densely distributed orbicules. These orbicules are also found all over the external face and margins of the elaters, while the internal face is smooth and lack orbicules. Viewed with TEM, the exospore is a thick layer of fine granular material, while perispore is a thinner layer of dense, separate orbicules. The elaters are composéd by two layers of fibrillar material : an inner layer with longitudinally oriented fibrils and an outer, thicker and less dense layer with fibrils transversely fibrils and abundant, external orbicules. It is suggested that the processes of ontogeny and characters of the sporoderm are relatively constant in Equisetum ; however, sporogenesis in E. bogotense is synchronous and this condition has been observéd so far only in E. giganteum, a tropical genus also found in Colombia.<br/>Studies on some reproductive traits in Equisetum species are scarce and valuable to understand species distribution. Therefore, a detailed study of the sporogenesis process and spore development in E. bogotense is presented, with an analysis of the main events during meiosis, maturation of spores, spore wall ultrastructure, orbicules and elaters. Specimens were collected from 500 to 4500 m in Cauca, Colombia. Strobili at different maturation stages were fixed, dehydrated, embedded in resin, and ultra-microtome obtained sections were stained with Toluidine blue. Observations were made with optical microscopy with differential interference contrast illumination technique (DIC), transmission and scanning electron microscopy (TEM and SEM). Ultrathin sections (70-80 microm) for TEM observations were stained with uranyl acetate and lead citrate; while samples for SEM observations, were fixed, dehydrated in 2.2-dimethoxypropane and dried at critical point as in standard methods. Strobili have numerous mature sporangiophores, each one with a peltate structure, the scutellum, bearing five-six sessile sporangia attached to the axis of strobilus by the manubrium. Immature sporocytes (spore mother cells) are tightly packed within the young sporangia. The sporocytes quickly undergo meiosis, by passing the stage of archesporium and give origin to tetrads of spores. The tapetum loses histological integrity during early stages of sporogenesis, intrudes as a plasmodial mass into the cavity of the sporangium, partially surrounding premeiotic sporocytes, and then, tetrads and adult spores. The tapetum disintegrates towards the end of the sporogenesis, leaving spores free within the sporangial cavity. Spores present several cytological changes that allow them to achieve greater size and increase the number of plastids, before reaching the adult stage. Sporoderm includes three layers external to the cytoplasmic membrane of the spore cell, and they are pseudoendospore, exospore and perispore. Viewed with SEM, the exospore is smooth to rugulate, with micro perforations, while the perispore is muriform, rugate, with narrow, delicate, discontinuous, randomly distributed folds delimiting incomplete, irregular areolae, externally covered by of different size, densely distributed orbicules. These orbicules are also found all over the external face and margins of the elaters, while the internal face is smooth and lacks orbicules. Viewed with TEM, the exospore is a thick layer of fine granular material, while perispore is a thinner layer of dense, separate orbicules. The elaters are composed of two layers of fibrillar material: an inner layer with longitudinally oriented fibrils and an outer, thicker and less dense layer with fibrils transversely fibrils and abundant, external orbicules. It is suggested that the processes of ontogeny and characters of the sporoderm are relatively constant in Equisetum; however, sporogenesis in E. bogotense is synchronous and this condition has been observed so far only in E. giganteum, a tropical genus also found in Colombia.<br/>