Alloteropsis Semialata Research Articles

Seasonal use of savanna landscapes by the Gouldian finch, Erythrura gouldiae, in the Yinberrie Hills area, Northern Territory

The diet, attributes of feeding sites and patterns of seasonal movements of a population of the Gouldian finch, Erythrura gouldiae, were studied in the Yinberrie Hills area north of Katherine in the Northern Territory. In the dry season (April–November) Gouldian finches foraged mostly on burnt ground and fed on exposed seed of annual grasses, especially seed of spear-grass, Sorghum spp. In the wet season (December–March) Gouldian finches fed on seed of a sequence of perennial grass species, including Themeda triandra, Alloteropsis semialata, Chrysopogon fallax and Heteropogon triticeus. Gouldian finches undertake regular seasonal shifts in habitat, from breeding areas in hill woodland in the dry season to adjacent lowlands throughout much of the wet season, in response to seasonal changes in food availability. There is an annual pulse in abundance of fallen seed in the early dry season that is depleted to near zero levels by germination of annual grasses early in the wet season. Thereafter, finches depend on seed from other sources, principally ripe and ripening seed of perennial grasses. Observations over three successive wet seasons suggest that Gouldian finches track seed resources provided by seeding perennial grasses over an extensive area of lowland grassy woodland adjacent to the breeding area, favouring small patches of grassy woodland for brief periods until seed fall. There were subtle differences between years in the types of resources used. Management of Gouldian finch populations will entail protection and management of the full range of grassland habitats used throughout the annual cycle, and will require predictive knowledge of the causes of patterning of seed resources and probably an ability to exert control over the timing and extent of fires in fire-prone seasonal savanna landscapes.

Investigation of the potential ingestion rates of different sourveld grasses by cattle and sheep

Quantification of the potential ingestion rates of different grasses is important for modelling purposes but is difficult to achieve under field conditions. The ingestion rates of the sourveld species Alloteropsis semialata, Andropogon appendiculatus, Cynodon dactylon, Eragrostis plana, Heteropogon contortus, Hyparrhenia hirta, Themeda triandra and Tristachya leucothrix were determined by presenting plants growing in pots to confined sheep and a single steer. Sheep intake rates were highest for H. contortus (6.82g DM min -1 ) and lowest for A. appendiculatus (4.01g DM min -1 ) but most between-species differences were non-significant. Steer intake rates were highest for E. plana and A. semialata (32g DM min -1 ) and lowest for H. hirta (24.3g DM min -1 ) but again, most between-species differences were non-significant. The results obtained suggest that there is little difference in the potential ingestion rate of most sourveld species and indicate that the methodology employed has potential as research tool. Keywords: alloteropsis semialata ; andropogon appendiculatus ; bite rate; bite size; botany; cattle; condition; cynodon dactylon ; dohne agricultural development institute; eragrostis plana ; grass; grasses; heteropogon contortus ; hyparrhenia hirta ; ingestion; intake; intake rate; methodology; modelling; plant structure; plants; quantification; sheep; sourveld grass; south africa; themeda triandra ; tristachya leucothrix African Journal of Range & Forage Science , Vol. 13(2), pp. 49-53

Effects of intensity and height of shading on the tiller initiation of six grass species from the Highland sourveld of Natal

Grass species of the conservation areas of the Natal Drakensberg are divided into two ecological groups. Decreaser species are those which decrease with over- or under-utilization, while increaser I species are those which increase with under-utilization. The effect of intensity and height of shading on decreaser species (Themeda triandra, Heteropogon contortus and Trachypogon spicatus) and increaser species (Tristachya leucothrix, Harpochloa falx and Alloteropsis semialata) was determined in potted plant trials. Results of this study support the hypothesis that decreaser species were more sensitive to low light intensities (30% full sunlight) than increaser species. These two species groups did not, however, differ in their response to height of shading. The results suggest that different fire regimes resulting in changes in canopy cover and light quality are important mechanisms in regulating tiller initiation in perennial grasses.

New Structural/Biochemical Associations in Leaf Blades of C4 Grasses (Poaceae)

Forty-three previously uninvestigated, mainly Australian, grass species (Poaceae) were assayed for activities of C4 acid decarboxylating enzymes (NADP-malic enzyme, NADP-ME; NAD-malic enzyme, NAD-ME; PEP carboxykinase, PCK). Twenty-five species exhibit long-established ('classical') associations between C4 type and structural features of leaf blade vascular bundles. However, Panicum virgatum and Triraphis mollis are NAD-ME species with structure like that of 'classical' PCK species. Seven Enneapogon species and Triodia scariosa are NAD-ME but are structurally intermediate between 'classical' NAD-ME and PCK species. Alloteropsis semialata (R.Br.) Hitch. is PCK, the first recorded non-NADP-ME XyMS - species, and Pheidochloa gracilis S.T. Blake and five Eriachne species are the first known XyMS+ NADP-ME species, with either centripetal or centrifugal/peripheral PCR (photosynthetic carbon reduction, or Kranz) cell chloroplasts. A suberised lamella is absent from the PCR cell walls of all species with an even PCR bundle sheath outline, irrespective of C4 type, as well as from NADP-ME Aristida, Eriachne and Pheidochloa; it is present in all other species with an uneven outline and centrifugal/peripheral chloroplasts. Pheidochloa gracilis and Eriachne spp. have unusually well-developed grana in PCR cell chloroplasts for NADP-ME species. This new-found structural/biochemical diversity is discussed in relation to high [CO2] maintenance in PCR cells.

The taxonomic position of C3 and C4 <i>Alloteropsis semialata</i> (Poaceae) in southern Africa

Alloteropsis semialata (R. Br.) Hitchc. sensu Chippindall (1955) and Clayton (in press) is the only known grass species in which elements with both non-Kranz and Kranz leaf blade anatomy, and therefore with C3 and C4 photosynthetic pathways are included. In the past, two taxa had been recognized, but the characters used to separate them were found to be unreliable, so they were united. However, study of voucher specimens for anatomical and physiological work has shown that C3 and C4 taxa may be separated on the basis of morphological characters that differ from those considered in the past. Therefore, two taxa are again recognized, this time at the rank of subspecies, and the name Alloteropsis semialata subsp. eckloniana (Nees) Gibbs Russell stat. nov. is published.

Intraspecifíc variability in <i>Alloteropsis semialata</i> (R. Br.) Hitchc.

Intraspecific variability in Alloteropsis semialata (R. Br.) Hitchc. is shown ultrastructurally with particular regard to the structure of the bundle sheath and the development of the dimorphic chloroplasts in both the C3 and C4 forms of this species. A. semialata is known to possess two distinct anatomical forms — Kranz and non-Kranz — within one species and occurring within a single ecological niche. Kranz and non-Kranz anatomy is known to be correlated with C3 and C4 physiology respectively. Transverse sections of leaf portions taken at midsheath, at the ligule and at midlamina show plastids with different morphologies at different ontogenetic stages. Plastid form is related to the stage of development, the influence of light on the emerging leaf and the C3 or C4form of A. semialata. Stages from amyloplast to chloroplast are investigated with regard to fine structure. Leaf transverse sections are examined microscopically and formation of new bundles, chiefly in the lamina is traced. Differences in anatomy and distribution of vascular bundles are more evident in the lamina than in the colourless leaf sheath. Both C3 and C4 forms of A. semialata are found to show chloroplast dimorphism in vascular bundle sheath and mesophyll cells. This is shown to differ in the two forms. The specialized chloroplasts of the Kranz sheath are shown to develop in the inner or mestome sheath, and not in the parenchyma sheath as in some other members of the Kranz Panicoideae. Features of A. semialata, such as the double bundle sheath, granal chloroplasts and large numbers of mitochondria in bundle sheath cells, in the C4 form, question the current classification of this grass as a malate former.

C3 and C4 Photosynthetic and Anatomical forms of Alloteropsis semialata (R.Br.) Hitchcock

C3 and C4 Photosynthetic and Anatomical forms of Alloteropsis semialata (R.Br.) Hitchcock

Occurrence of the suberized lamella in leaves of grasses of different photosynthetic types. I. In parenchymatous bundle sheaths and PCR (?Kranz?) sheaths

Leaf blades of 42 grasses (Poaceae) have been examined ultrastructurally for the occurrence of a suberized lamella in walls of parenchymatous bundle sheaths and PCR (= “Kranz”) sheaths in both large and small vascular bundles. The sample includes species from a range of major grass taxa, and represents all photosynthetic types found in the grasses. Three grasses with unusual C4 leaf anatomy were also included:Alloteropsis semialata, Aristida biglandulosa, Arundinella nepalensis. The presence of a suberized lamella in PCR cell walls was perfectly correlated with photosynthetic type. All PEP-carboxykinase type and NADP-malic enzyme type C4 species examined possessed a suberized lamella in outer tangential and radial walls, but with variable presence in inner tangential walls. PCR cells of bothAlloteropsis semialata andArundinella nepalensis also possessed a suberized lamella. A lamella was totally absent from parenchymatous bundle sheath cells of the C3 species examined (5 spp.) and ofPanicum milioides, a C3-C4 intermediate. It was also absent from PCR cells of NAD-malic enzyme type C4 species (14 spp.) andAristida biglandulosa. The results are discussed in relation to the leakage of CO2 from PCR cells, and to differences between C4 types in δ13C values, chloroplast position in PCR cells, and other anatomical characteristics.

An ontogenetic study with special reference to leaf development in C3and C4forms ofalloteropsis semialata

Abstract This ontogenetic study conducted at light and electron microscope level, describes several aspects of leaf development in C3 and C4 forms of Alloteropsis semialata. Emphasis is placed on the distribution and anatomy of vascular bundles as seen in transverse sections. The derivation of the specialized photosynthetic tissue of the Kranz sheath, which characterizes the C4 form, is traced in the inner or mestome layer of the double bundle sheath. The lamina and sheath in successive leaves of comparable age in the two forms were used. The proportion of photosynthetic tissue present in sections taken at midlamina is assessed quantitatively using a planimeter. The main conclusions drawn from this study are summarized as follows: 1. lamina and sheath in leaves of A. semialata, in common with other grasses, are derived from different meristems, show different patterns of vascularization and mature at different rates, the tip representing an older portion of the leaf than the base; 2. the differences in bundle sheath anatomy between C3 (non‐Kranz) and C4 (Kranz) forms of A. semialata are more obvious in the lamina than in the colourless sheath, and 3. the proportion of chlorenchymatous tissue is higher in the C4 than in the C3 leaf.

Variability in leaf surface features and water efficiency utilisation in C3and C4forms ofalloteropsis semialata(R. Br.) hitchc.

Alloteropsis semialata (R. Br.) Hitchc. Occupies a unique position both taxonomically and physiologically in the Gramineae in that C3 and C4 photosynthetic and anatomical forms exist within a single taxonomic species. Both forms have been collected from a single ecological niche in the Transvaal highveld. This study shows further morphological and anatomical differences between the two forms with respect to stomatal size, and frequency of distribution, as well as differing epidermal cell characteristics. In addition physiological differences between the two forms are established with regard to photosynthetic rates, transpiration rates, and boundary layer and stomatal resistances. The C4 form was found to be more efficient with respect to water utilization efficiency. Keywords: alloteropsis semialata; botany; characteristics; distribution; grasses; leaves; photosynthetic rate; plant physiology; south africa; stomatal resistance; transpiration rate; transvaal highveld; water use efficiency; water utilization

Descriptions and host ranges of the sorghum midge, Contarinia sorghicola (Coquillett) (Diptera: Cecidomyiidae), and of eleven new species of Contarinia reared from Gramineae and Cyperaceae in Australia

AbstractDetailed taxonomic studies of adult Cecidomyiidae reared from inflorescences and seed-heads of species of Gramineae and Cyperaceae during field surveys in Queensland and the Northern Territory of Australia in 1970–73 established that Contarinia sorghicola (Coq.) is restricted to non-indigenous crop and weed species of Sorghum section Sorghum that have been introduced to Australia by man and that three morphologically distinct species of Contarinia occur on native Australian grass species of Sorghum section Parasorghum. An earlier report that the wild grasses Dichanthium, Bothriochloa and Eriochloa serve as alternative hosts of C. sorghicola was not confirmed by detailed examination of long series of specimens reared from these hosts, nor was the pest species found on any other genera of Gramineae. It is therefore concluded that, in Australia, C. sorghicola has been spread (probably in contaminated seed) and maintained by grain and forage sorghums and that wild grasses are not potential sources of crop infestation. Eleven new species are described: C. roperi sp. n. and C. plumosi sp. n. from Sorghum plumosum; C. intrans sp. n. from S. intrans and S. stipoideum; C. sehimae sp. n. from Sehima nervosum; C. bothriochloae sp. n. from B. bladhii; C. dichanthii from D. annulatum var. fecundum and D. tenuiculum and possibly from D. affine and D. sericeum; C. passlowi sp. n. from D. annulatum var. fecundum; C. alloteropsidis sp. n. from Alloteropsis semialata; C. brevipalpis sp. n. from Eragrostis brownii; C. scirpi sp. n. from Scirpus lacustris and C. fimbristylis sp. n. from Fimbristylis bisumbellata. Characters of the female cerci were especially useful in diagnosing species, making it easier to identify females than males. Cecidomyiids of the genus Geromyia were reared from Setaria and cecidomyiids of the genus Lasioptera were reared from ten grass genera and one sedge genus during the surveys, but this material is not dealt with in detail. The needs for further field work and taxonomic studies are stressed and it is suggested that apertures on the dorsal surface of abdominal segment VIII in female C. sorghicola may be the openings of sex pheromone glands and would merit further detailed investigation.

Anomalous vascular bundle sheath structure in <i>Alloteropsis semialata</i> leaf blades

Alloteropsis semialata (R.Br.) Hitchc. of the Paniceae, would be expected to exhibit typical eupanicoid leaf anatomy with a single bundle sheath of large parenchymatous cells with specialized chloroplasts and radially-arranged chlorenchyma. Specimens from South Africa showed the following bundle-sheath and mesophyll deviations from the generalized panicoid model: 1. bundle sheath is double; 2. inner bundle sheath is composed of large cells with specialized chloroplasts; 3. outer sheath consists of many smaller cells with few, or without chloroplasts; 4. outline of the third- order bundles is tall and narrow; 5. chlorenchyma is not radially arranged. Other specimens of A. semialata, however, were found to have a large-celled outer bundle sheath devoid of chloroplasts and with indistinctly radiate chlorenchyma.

Ecology of The Common Mole-Rat (Cryptomys Hottentotus) In Rhodesia

The common mole-rat (Cryptomys hottentotus) was studied for 8 months, principally on the campus of the University College of Rhodesia and Nyasaland at Salisbury in Southern Rhodesia. Eighty-eight mole-rats were captured with snares set below ground in tunnel systems dug by the animals in search of food. Small mounds are formed resembling those of moles and pocket gophers in North America. When the ground is moist and easily dug, much time is spent in storing food within an intricate home burrow system beneath large termite hills. In the dry season as the ground becomes dry and hard at the surface, the molerats no longer push up mounds but redistribute the loose soil in abandoned tunnels. During the rainy season much of their habitat is flooded and they are restricted to the home burrows. Captive mole-rats of the genera Cryptomys and Heliophobius dug with the incisor teeth, and used the feet and tail to push loose earth along the tunnel and onto the surface of the ground. Vibratory movements of the hind limbs tamped the loose earth into a plug that blocked the burrow opening. The mole-rats ate, almost exclusively, the bulbous bases of black seed grass (Alloteropsis semialata). A density of three mole-rats per acre was estimated for the 26.8-acre study plot. The scarcity of pregnant females and the absence of sperm in males taken during the study indicate that the breeding season must occur in the middle of the rainy season. Small Utters, a large number of adults and the closed burrow system all indicate a low mortality rate in the species. The low mobility and high degree of isolation of local populations are associated with a high degree of variability in coat color and head markings.