Adaptive morphoanatomy and ecophysiology of Billbergia euphemiae, a hemiepiphyte Bromeliaceae

Habitats under distinct selective pressures exert adaptative pressures that can lead individuals of the same species to present different life strategies for their survival. The aim of this study was to analyse morphoanatomical and physiological traits for identification of adaptive ecological strategies related to both terrestrial and epiphytic life phases of Billbergia euphemiae. It was verified that B. euphemiae showed lower height, as well smaller length, width and foliar area in epiphytic phase than in terrestrial phase. Concerning to foliar anatomy, the thicknesses of leaf and water-storage parenchyma were higher in terrestrial phase, as densities of stomata and scales on the abaxial surface were higher in epiphytic phase. About the contents of photosynthetic pigments, only chlorophyll a/b ratio showed differences between life phases. In both habits, plants exhibited roots with absorption hair. In epiphytic phase, roots exhibited higher velamen thickness, smaller outer cortex, higher number of inner cortex cell layers and higher number of protoxylem poles. Thus, B. euphemiae individuals in epiphytic exhibited lots of traits related to water retention, once these plants are not into the ground. Besides, the plasticity observed may contribute for survival of this group in habitats submitted to modifications (e.g., climate change and other variations caused by human interference).

ANATOMY OF THE CLADODES AND ECOLOGICAL ADAPTATION IN OPUNTIA (CACTACEAE) FROM THE PROVINCE OF BUENOS AIRES (ARGENTINA)

In this paper we examine the cladodes anatomy of Opuntia arechavaletae, O. aurantiaca, O. bonaerensis, O. elata, O. ficus-indica, O. megapotamica, O. penicilligera, O. sulphurea var. pampeana, and O. ventanensis that grows in the province of Buenos Aires, Argentina. The aim of this study was to establish diagnostic features in order to deepen knowledge of ability of adaptation to the environmental. Fresh and herbarium samples were prepared according to usual methods for light microscope. Histochemical techniques were performed to identify starch, mucilage and oxalate salts. The main traits found were: epidermis smooth and uniseriate, covered by a thin cuticle and epicuticular waxes; large stomata in low density, located at level with a deep substomatal chamber; a multilayered collenchyma including crystal layer; water storage parenchyma, and in vascular bundles a special water-storage cell type, resistant to collapse, and perhaps having some water transfer function we named ‘intermediate cells’ which form masses in the xylem of O. megapotamica, O. penicilligera, O. sulphurea var. pampeana, and O. ventanensis, which grows in xeric, saline and stone soils.

A COMPARATIVE ANATOMICAL CHARACTERISTICS OF THE STEMS OF CLIMBING PLANTS IN ARALAM WILD LEFE SANCTUARY, KANNUR

Climbing plants differ from self-supporting plants, such as shrubs and trees, in a range of characteristics. The most notable is the mechanical properties of the stem Comparison of the differentiated anatomical structures recorded in ten species of the climbing plants. The plants selected for the present study are Ampelocissus latifolia,(Vitaceae), Lygodium flexuosum (Lygodiaceae), Centrosema virginianum(Fabaceae), Tinospora cordifolia,(Menispermaceae), Wattakakka volubilis (Asclepiadaceae) Cyclea peltata (Menispermaceae), Calycopteris floribunda (Combretaceae) Pothos scandens(Araceae) Ipomoea separia (Convolvulaceae) and Piper nigrum (Piperaceae). The stems of climbing plants are characterized by the scarcity of supporting cells (fibers) and an increase in the diameter of the xylem vessels. The study con firms that they show a greater diversity of organization than other plant life forms. This anatomical radiation couldprobably not exist without the achievement of a wide range of secondary growth processes. Many dicotyledons, notably those with a climbing habit, show interesting secondary structure which differs from the more usual type described, therefore, sometimes termed anomalous. The variant secondary growth isparticularly widespread in tropical climbers. It is speculated that variant growth can increase stem flexibility, protect the phloem, increase storage parenchyma, aid in clinging to supports, limit physical disruption of vascular tissues during twisting and bending, and promote wound healing after girdling.

A COMPARATIVE ANATOMICAL CHARACTERISTICS OF THE STEMS OF CLIMBING PLANTS IN ARALAM WILD LIFE SANCTUARY, KANNUR

Climbing plants differ from self-supporting plants, such as shrubs and trees, in a range of characteristics. The most notable is the mechanical properties of the stem Comparison of the differentiated anatomical structures recorded in ten species of the climbing plants. The plants selected for the present study are Ampelocissus latifolia, (Vitaceae), Lygodium flexuosum (Lygodiaceae), Centrosema virginianum (Fabaceae), Tinospora cordifolia, (Menispermaceae), Wattakakka volubilis (Asclepiadaceae) Cyclea peltata (Menispermaceae), Calycopteris floribunda (Combretaceae) Pothos scandens (Araceae) Ipomoea separia (Convolvulaceae) and Piper nigrum (Piperaceae). The stems of climbing plants are characterized by the scarcity of supporting cells (fibers) and an increase in the diameter of the xylem vessels. The study con firms that they show a greater diversity of organization than other plant life forms. This anatomical radiation couldprobably not exist without the achievement of a wide range of secondary growth processes. Many dicotyledons, notably those with a climbing habit, show interesting secondary structure which differs from the more usual type described, therefore, sometimes termed anomalous. The variant secondary growth isparticularly widespread in tropical climbers. It is speculated that variant growth can increase stem flexibility, protect the phloem, increase storage parenchyma, aid in clinging to supports, limit physical disruption of vascular tissues during twisting and bending, and promote wound healing after girdling.

Cellular pathways of source leaf phloem loading and phloem unloading in developing stems of Sorghum bicolor in relation to stem sucrose storage

Cellular pathways of phloem loading in source leaves and phloem unloading in stems of sweet Sorghum bicolor (L.) Moench were deduced from histochemical determinations of cell wall composition and from the relative radial mobilities of fluorescent tracer dyes exiting vascular pipelines. The cell walls of small vascular bundles in source leaves, the predicted site of phloem loading, contained minimal quantities of lignin and suberin. A phloem-loaded symplasmic tracer, carboxyfluorescein, was retained within the collection phloem, indicating symplasmic isolation. Together, these findings suggested that phloem loading in source leaves occurs apoplasmically. Lignin was restricted to the walls of protoxylem elements located in meristematic, elongating and recently elongated regions of the stem. The apoplasmic tracer, 8-hydroxypyrene-1,3,6-trisulfonic acid, moved radially from the transpiration stream, consistent with phloem and storage parenchyma cells being interconnected by an apoplasmic pathway. The major phase of sucrose accumulation in mature stems coincided with heavy lignification and suberisation of sclerenchyma sheath cell walls restricting apoplasmic tracer movement from the phloem to storage parenchyma apoplasms. Phloem unloading at this stage of stem development followed a symplasmic route linking sieve elements and storage parenchyma cells, as confirmed by the phloem-delivered symplasmic tracer, 8-hydroxypyrene-1,3,6-trisulfonic acid, moving radially from the stem phloem.