This study was conducted to investigate the effects of four drip irrigation treatments on five fruiting characteristics of cotton (Gossypium hirsutum L.) using periodic observations to gauge the relative impact of these effects over time. The fruiting characteristics measured were: (1) number of flowers, (2) percent boll set, (3) number of bolls, (4) weight boll-1, and (5) seedcotton production. The irrigation treatments included four levels that in total season applied irrigation equaled 60, 68, 76, and 83 cm of water. Periodic observations included three, 3-week-intervals from the onset of flowering (26 June) to cutout (29 August). Results indicate that irrigation treatments had a significant effect on all characters measured, only in the later stages of development (later in the season) with higher amounts of irrigation applied producing higher levels of each character measured. Significant differences were found among periods of observation for all characters measured.

No description available.

Bibliography: leaves 105-121. / viii, 133, [28] leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This thesis tests the hypothesis that plant strategies to respond to seasonal flooding can be used to predict their tolerance to variation in water regime. The studies illustrate contrasting strategies for survival in seasonally fluctuation water levels. These are tested in the field against similar species. Plants are surveyed at four stages of flooding at Bool Lagoon. The morphologically plastic species, V. reniformis and Triglochin procerum, respond to flooding with taller shoots and increased investment in photosynthetic tissue. It is concluded that the reproductive effort is much lower in the field than in the pond experiments, and changes in the population density of both species are not related to water regime. / Thesis (Ph.D.)--University of Adelaide, Dept. of Botany, 1997?

Bibliography: leaves 105-121. / viii, 133, [28] leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This thesis tests the hypothesis that plant strategies to respond to seasonal flooding can be used to predict their tolerance to variation in water regime. The studies illustrate contrasting strategies for survival in seasonally fluctuation water levels. These are tested in the field against similar species. Plants are surveyed at four stages of flooding at Bool Lagoon. The morphologically plastic species, V. reniformis and Triglochin procerum, respond to flooding with taller shoots and increased investment in photosynthetic tissue. It is concluded that the reproductive effort is much lower in the field than in the pond experiments, and changes in the population density of both species are not related to water regime. / Thesis (Ph.D.)--University of Adelaide, Dept. of Botany, 1997?

Chlorella vulgaris and Chlorella pyrenoidosa were compared relative to their abilities to grow at osmotic potentials of -0.1, -0.5, -1.0, -1.5, -2.0 MPa, [polyethylene glycol(PEG)-induced], and for osmotically-induced changes in lipid composition. C. vulgaris growth was inhibited as osmotic potentials decreased, while C. pyrenoidosa growth was moderately inhibited at -2.0 hPa. C. vulgaris produced increasing concentrations of triglycerides and sterol esters and decreasing levels of polar lipids and sterols as osmotic concentrations increased. Polar lipids, triglycerides, and sterols declined in C. pyrenoidosa while steryl esters remained constant. Ratios of free sterols to polar lipids were 10-fold greater in C. pyrenoidosa and were unaffected by reduced osmotic potentials. In C. vulgaris the sterol to polar lipid ratio declined. Decreasing osmotic potentials in a continuous culture of C. vulgaris, lowered cell lipid concentration, and had no effect on chlorophyll concentrations. The greatest decrease occurred as the osmotic potential decreased from -0.1 to -0.5 HPa. Decreasing osmotic potential caused the phospholipid concentrations to decline. Saturation of triglycerides and free fatty acids increased and decreased, respectively, while polar lipids remained fairly constant. However, the sterol to phospholipid ratio increased as the osmotic potential was lowered. BAS 13-338 (4-chloro-5-(dimethylamino)-2-phenyl-5- 3(2H)pyridazinone) had no effect on C. vulgaris resistance to osmotic stress, but caused growth inhibition as concentrations increased. However, BAS 13-338 was effective in decreasing growth inhibition of C. vulgaris grown in inhibitory levels of ethanol. BAS 13-338 had differing effects on the lipid composition of C. vulgaris when grown in PEG at an osmotic potential of -1.5 MPa compared to -0.1 MPa with 0.33% ethanol. The greatest effects were observed in the ethanol treatments where the qualitative composition of precursor sterols increased as the level of BAS 13-338 increased. This investigation confirmed the important role of lipids in responding to environmental stress through observations of lipid responses to osmotic stress and by manipulation of lipid concentrations using BAS 13-338. Resistance to ethanol inhibition but not osmotic inhibition was achieved in the investigation. / Ph. D.

Studies were conducted to evaluate the effect of pre-irrigation media moisture deficit, irrigation application rate, and intermittent irrigation on irrigation efficiency [(amount applied - amount leached) amount applied' 100] of spray stake-irrigated, container-grown plants. In the first experiment, pine bark-filled containers were irrigated to replace moisture deficits of 600, 1200, or 1800 ml. Deficits were returned in single, continuous applications at application rates of 148, 220, and 270 ml/min. Application rate did not affect irrigation efficiency. Efficiency decreased with increased medium moisture deficit. In the second experiment, containers, at 600 ml media moisture deficits, were irrigated with 400 or 600 ml (65% and 100% water replacement, respectively). Irrigation volumes were returned in a single, continuous application or in 100ml applications with 30 min intervals between irrigations (intermittent). Irrigation efficiency was greater with intermittent irrigation, 95 % and 84 % for 400 and 600 ml replacement, respectively, than with continuous irrigation, 84% and 67% for 400 and 600 ml replacement, respectively. When applied intermittently, most water loss from containers occurred after 400 ml were applied. In the third experiment, containers were irrigated with 600 ml (100% water replacement) in 50, 100, or 150 ml applications with 20, 40, or 60 min intelVals between applications. A control was included in which 600 ml was applied in a single, continuous application. Irrigation efficiency increased with decreasing application volume and increasing length of interval between applications. The greatest efficiency (86%) was produced with an irrigation regimen of 50 ml applications with at least 40 min between applications. The control treatment (continuous) produced an irrigation efficiency of 62%. When applied intermittently, most water loss from containers occurred after a total of 300 ml were applied. / Master of Science

Dissertation (PhD (Bosb))--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: This study was conducted to evaluate and compare the water and nutrient relations of three indigenous deciduous tree species, viz., Cordia africana Lam., Croton macrostachyus Del., Millettia ferruginea (Hochst.) Baker and two widely planted eucalypts, viz., Eucalyptus camaldulensis Dehnh and Eucalyptus globulus Labill from Ethiopia. The study was organized as glasshouse and field observations in Ethiopia. Owing to the lack of baseline studies on the water and nutrient relations of the deciduous tree species, the glasshouse experiments involved a wide range of water and nutrient applications. Seedlings were grown with the supply of various levels of water and nutrients during which gas exchange, water potential, relative water content, tissue nutrient content and biomass production were measured. The field observations were limited to the study of surface root distribution and leaf nutrient composition of mature trees and their effects on soil nutrient pool. The observations were made on isolated trees and mixed or pure stands of trees in Badessa area, Eastern Ethiopia. The field site was selected because of the availability of the study species and suitability of the trees for the study. In the glasshouse, increased water deficit significantly reduced predawn leaf water potential, relative water content, stomatal conductance, photosynthetic rate, whole plant water use efficiency, plant height, diameter, leaf area and biomass production. Both of the eucalypts did not grow faster than the deciduous species under well-watered conditions unlike under water stress conditions. C. macrostachyus and C. africana had higher transpiration rates and tissue nutrient accumulations than the other species. They also demonstrated higher biomass allocation to roots than all the other species to support the intensive water and nutrient uptake rate. Due to the ability to re-orient its leaves to avoid direct solar irradiance, M. ferruginea maintained higher tissue water potential and relative water content than all the other species under water stress regimes. The impact of imposed drought was quick and more damaging to the eucalypts compared to the deciduous tree species indicating that the eucalypts may not survive extreme drought conditions unlike the deciduous species that drop their leaves and may remain dormant for weeks. The current study gave new experimental proof that E. globulus was more vulnerable to drought than E. camaldulensis. Soil N stress resulted in an overall reduction of tissue N concentration, N:P ratio, photosynthetic rate, stomatal conductance and photosynthetic water use efficiency in all the species studied. Pants with high foliar nitrogen concentration had higher photosynthetic capacities indicating that N plays a key role in photosynthesis and growth of all the studied species. The current study showed that for all the tree species, more attention has to be given to soil N than to P as soil P had minor effects on the photosynthetic activities of plants of all species compared to N.The investigation on tissue nutrient composition confirmed that N:P ratio could be used to detect Plimitation in plants. However, N:P ratio could not distinguish between N-limitation and combined limitations of N and P. The study of isolated C. africana and C. macrostachyus trees on soils in Badessa, Eastern Ethiopia indicated improved soil N, P and K under tree canopies whereas no effects were observed on the other soil nutrients studied. Similar to glasshouse conditions, C. macrostachyus and C. africana produced extensive surface roots, interfering with crops grown in association. Due to their high nutrient cycling potential the net effect on soil was positive. Comparison of E. camaldulensis woodlot and a mixed stand composed of deciduous species indicated that the fine root biomass in the surface soil under E. camaldulensis was about three times that under the mixed stand. The fine root biomass of E. camaldulensis inside the stand and 10 meters away from the stand were comparable in the surface soils showing the presence of root competition with adjacent crops. Therefore, planting of E. camaldulensis in association or adjacent to croplands should be avoided. Nutrient and carbon pool of soil inside the mixed stand was generally higher than that of E. camaldulensis indicating that trees of the mixed stand recycled more nutrients to the soil. / AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om die verskille tussen water- en voedingstofverhoudings van drie inheemse blaarwisselemde boomsoorte te vergelyk, viz., Cordia africana Lam., Croton macrostachyus Del., Millettia ferruginea (Hochst.) Baker en twee bekende eucalyptus spesies, viz., Eucalyptus camaldulensis Dehnh en Eucalyptus globulus Labil van Etiopië. Die studie het bestaan uit kweekhuis- en veldobservasies in Etiopië. As gevolg van beperkte navorsing ten opsigte van water- en voedingstofverhoudings in bladwisselende boomsoorte, het die kweekhuis-eksperimente bestaan uit 'n wye verkeidenheid water- en voedingstoftoetse. Saailinge is gegroei deur verskillende vlakke van water- en voedingstowwe by te voeg. Gaswisseling, waterpotensiaal, relatiewe hoeveelheid water, hoeveelheid voedingstowwe en produksie van biomassa is gemeet. Die veldobservasies was beperk tot oppervlak-wortelverspreiding en blaarvoedingstof hoeveelhede van volwasse bome, sowel as die effek op grondvoedingstowwe. Observasies was beperk tot geïsoleerde, gemengde en een spesie opstande, in die Badessa area, Oos Etiopië. Die studiearea was gekies op grond van die voorkoms van die gekose boomsoorte, sowel as die toepaslikheid van die bome vir die studie. In die kweekhuis is gevind dat die verhoogte watertekort die pre-sonop blaarwaterpotensiaal, relatiewe hoeveelheid water, stomatiese geleiding, fotosintetiese tempo, heelplant water-gebruikseffektiwiteit, plant hoogte, diameter, blaararea en biomassa produksie beduidend verminder het. Nie een van die eucalyptus spesies het vinniger as die bladwisselende spesies onder voldoende hidrasie gegroei nie. Dit was egter nie die geval onder die waterbeperkte toestande nie. C. macrostachyus en C. africana het ‘n hoër transpirasie tempo sowel as weefselvoedingstof waardes gehad as die ander spesies. Hierdie boomsoorte se wortelbiomassa was ook meer as die ander spesies, om vir die tempo van water- en voedingstofopname te akkomodeer. As gevolg van die vermoë om blare te kan oriënteer om direkte sonlig te vookom, het M. ferruginea ‘n hoër water-weefselpotensiaal en relatiewe waterinname gehad in vergelyking met die ander boomsoorte in beperkte water toestande. Die impak van gëinisieerde droogte het vinnig voorgekom en het meer skade aan die eucalyptus aangerig in vergelyking met die bladwisselende boomsoorte. Dit dui aan dat die eucalyptus-spesie nie ekstreme droogte kan oorleef nie, waar bladwisselende spesies hul blare laat afval en vir weke aan een dormant kan bly. Hierdie studie gee eksperimentele bewyse dat E. globulus minder bestand is teen droogte as E. camaldulensis. Beperkte N in die grond het veroorsaak dat daar ‘n algemene vermindering van weefsel Nkonsentrasie, N:P ratio, fotosintetiese tempo, stomatiese geleiding en fotosintetiese watergebruiks effektiwiteit in al die bestudeerde spesies was. Plante wat oor hoër blaar-stikstofkonsentrasiesbeskik, het hoër fotosintetiese kapasiteite wat aandui dat N ‘n belangrike rol in fotosintese en die groei van al die bestudeerde spesies speel. Die oorhoofse bevindings van die studie was, dat daar meer aandag gegee moet word aan grond-N as P omdat grond-P net ‘n kleiner rol speel in die fotosintetiese aktiwiteite van plante van al die spesies in vergelyking met N. Die ondersoek na weefselvoedingstof hoeveelhede het bewys dat die N:P ratio gebruik kan word om P-tekorte in plante aan te dui. Die N:P ratio kan egter nie die verskil in N-tekorte en gekombineerde tekorte van N en P aandui nie. Die studie van die geïsoleerde C. africana en C. macrostachyus bome op grondtipes in Badessa, Oos Etiopië het verbeterde grond-N, P en K onder kroondak gebiede getoon, daar was egter geen verskille in die ander grondvoedingstowwe wat bestudeer is nie. In toestande gelykstaande aan die van die kweekhuis, het C. macrostachyus en C. africana meer oppervlaksswortels ontwikkel. Die toename aan oppervlakswortels het ingedring op gewasse wat in assosiasie gegroei is, dit het egter ‘n positiewe effek op die grond gehad as gevolg van die hoë voedingstof-siklus-potensiaal. Die E. camaldulensis opstand is gevergelyk met ‘n gemengde opstand van bladwisselende spesies waar daar gevind is dat die fynwortel biomassa in die oppervlak grond onder die E. camaldulensis ongeveer drie keer soveel was as die van onder die gemengde opstand. Kompetisie met aangrensende gewasse is aangeui deurdat die fynwortel biomassa van E. camaldulensis binne die opstand en 10 meter weg van die opstand vergelykbaar was in die oppervlakgronde. Dit dui dus aan dat die plant van E. camaldulensis in assosiasie of aangrensend aan gewasse vermy moet word. Die teenwoordigheid van voedingstowwe en koolstof in die grond van die gemengde opstand was oor die algemeen hoër as die van die E. camaldulensis. Dit is ‘n aanduiding dat die bome van die gemengde opstand meer voedingstowwe aan die grond verskaf.

Until the 1930s, flows of the Colorado River maintained approximately 781,060 hectares of wetlands in its delta. These wetlands provided important feeding and nesting grounds for resident and migratory birds as well as spawning and protection habitat for many fish and other invertebrate species. However, the Delta's wetlands started to disappear as water was used for agricultural and urban uses in the United States and Mexico. The 1944 United States-Mexico water treaty, which allocates 1.8 million m��/year to Mexico, did not define a minimum flow to maintain the Delta's ecosystems. The resulting degraded Delta lead to the perception in the 1980s that the Delta was a dead ecosystem. This study investigates whether this "dead Delta" perception is valid. Its central hypothesis is that regenerated vegetation in riparian and flood plain zones is associated with surplus river flows during the 1990s. A vegetation analysis, using satellite imagery and field methods, shows that native trees have regenerated during the last 20 years, and now account for 23% of vegetation in a 100 km, non-perennial, stretch of river below the United States-Mexico border. A spatial trend analysis using multi-temporal data on percent vegetation cover indicates that there are 6,320 hectares that show a significant increasing trend (p-value<0.05) in vegetation cover, with the Delta's riparian zone having at least 18% of its area showing this trend. The study estimates that once in four years February to April flow of 300 million m�� (at 80-120 m��/s) is sufficient to germinate and establish new cohorts of native trees, and highlights the need for smaller but more periodic flows in order to maintain wetland areas. It is concluded that there is clear evidence of the resilience of the Delta's ecosystems and that the "dead Delta" perception is no longer valid. There exist critical habitat in the Delta that needs to be protected, while there also exist short and long term opportunities to ecologically enhance and expand current habitat. Hydrological and ecological studies are needed to estimate specific water requirements for these areas in order to efficiently target them for immediate and long term conservation actions. / Graduation date: 2003

Bibliography: leaves 103-120. / 1 v. (various pagings) : ill. (some col.), maps ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Species interactions are dependent on the water regime, which affects the relative allocation to below (sediment resource acquisition) and above ground (C acquisition) parts. At shallow and regularily exposed sites, Baumea is the superior competitor. In Hacks and Bool Lagoon, South Australia, changing distribution patterns occur in deep and permanently flooded conditions, where Baumea dies back, paving the way for Triglochin to passively take it's place. / Thesis (Ph.D.)--Dept. of Botany, University of Adelaide, 1993

The Little Bow River Project was implemented in 2003 and includes Alberta’s newest dam. The Project involves tripling the diversion of water from the Highwood River to the Little Bow River and subsequently storing the water in the Twin Valley Reservoir. This MSc Thesis provided part of the environmental monitoring for that Project and particularly investigated the impacts of augmented flows on the river channel and riparian vegetation along the upper reach of the Little Bow River. An initial component of the long-term study was to determine the existing associations between fluvial geomorphic characteristics and riparian plant communities. Poplar (Populus balsamifera L.), willow (Salix bebbiana Sargent and S. exigua Nutt.) and wolf-willow (Elaeagnus commutata Bernh.) communities were located along the upper section of the river, where the channel had a steeper gradient and was narrower and more sinuous. Cattail (Typha latifolia L.) and grass (grasses and sedges) communities were generally located along the lower section of the river that was shallower in gradient, wider and straighter. Plant community distribution also reflected impacts from cattle grazing. Initial channel and vegetation responses in the first two years following the increase in flow augmentation were slight and included bank slumping, sediment scour and inundation of flooded zones. The initial responses are consistent with the primary prediction of channel widening and this will probably be associated with some changes in the adjacent riparian plant communities. / xiv, 139 leaves : ill. (some col.) ; 29 cm.