The potential for an adaptive response to global climatic change was evaluated for an annual C$ sb3$ weed, Brassica juncea, by performing a selection on fecundity for eight generations. During the selection, atmospheric carbon dioxide and temperature were gradually increased from current levels (370 $ rm mu L cdot L sp{-1}$ CO$ sb2$, 20$ sp circ$C) to conditions predicted during the next century by climate models (650 $ rm mu L cdot L sp{-1}$ CO$ sb2$, 23.6$ sp circ$C) including heat stress events at 32$ sp circ$C/26$ sp circ$C day/night), At the end of the selection, a reciprocal transplant experiment was conducted to identify genetic differences between control selection lines of plants and those selected under increasing CO$ sb2$ and temperature. I observed a genetic adaptation of early vegetative growth elevated CO$ sb2$ and temperature, which resulted in to 63% more biomass and 11% higher photosynthetic rates. Reproductive biomass, however, was decreased during the selection, mainly due to temperature stress, which disrupted flower development and induced strong maternal effects, counteracting the selection on fecundity.

Resumo: Caryota urens (Lam.) Mart., embora muito utilizada, há poucas informações sobre produção de mudas; desta forma, este trabalho teve como objetivo descrever a morfologia do diásporo (semente com o endocarpo aderido) e da plântula, bem como, estudar a interação entre temperatura e reposição de água em diferentes substratos. O delineamento experimental foi o inteiramente casualizado, em esquema fatorial 6 x 3, (seis temperaturas: 20, 25, 30, 35, 20-30 e 25-35°C; fotoperíodo de 12 horas e três reposições de água: areia - 50, 60 e 70%; esfagno e vermiculita - 80, 100 e 120%), com 4 repetições de 20 sementes. Anotou-se a cada dois dias o número de sementes que emitiram o botão germinativo para determinação da porcentagem de germinação e Índice de Velocidade de Germinação. Os dados foram analisados estatisticamente e as médias comparadas pelo Teste de Tukey (5%). As sementes são albuminosas, com endosperma rígido ocupando quase todo o interior do diásporo. O embrião é lateral, periférico e pouco diferenciado. Por meio da abertura de um opérculo circular no endocarpo, emerge o pecíolo cotiledonar que cresce e dilata em sua extremidade, originando a raiz primária e a parte aérea (plúmula), composta pela primeira folha juvenil completa (eófilo) e pinada (com 2 pinas de forma triangular). As temperaturas de 25ºC e 30ºC foram as mais adequadas e ainda, 25-35ºC, em esfagno e areia, independentemente da reposição de água. A porcentagem de germinação não foi influenciada pelas diferentes taxas de reposição de água, independentemente da temperatura. Em vermiculita, a germinação foi mais rápida repondo 100 e 120% de água. / Abstract: The palm tree Caryota urens (Lam.) Mart. is extensively used but poorly studied. The objective of this work was to describe the disseminule (the seed with endocarp attached to it) morphology and to evaluate the effects of the temperature, water reposition regimes, and types of substratum on seed germination. The experiment was set according to a completely random design in a factorial arrangement by which the seeds were set to germinate in a 12 hour photoperiod under combinations of different temperatures (the constant temperatures of 20, 25, 30, and 35ºC and the alternate temperatures of 20-30 and 25-35ºC) and different water reposition regimes (at 50, 60, and 70% in sand and at 80, 100, and 120%, in sphagnum and vermiculite). Each treatment was replicated 4 times. The number of germinated seeds (germination button) was counted every two days these data being also used to calculate the germination speed index. The seeds were found to be of the albuminous type with a hard endosperm occupying almost the entire inner space of the disseminule. The peripheral embryo occupies a lateral position and is little differentiated. The cotyledonous petiole emerges through a circular operculum in the endocarp, grows and enlarges its extremity, from which the aerial part (plumule) and the primary root are originated. The plumule is formed by the first juvenile complete bipinnate leaf (the eophylle, with two triangular leaves which gives them a tail fin appearance). In any of the used substrata the temperatures of 25 and 30ºC were the best for the germination of seeds; for sphagnum or sand, independently of the water reposition regime, temperatures of 25-35ºC too gave good results. Seed germination percentage was not affected by the different water reposition regimes independently of temperature. In vermiculite, germination is faster when water reposition takes place at 100 and 120%. / Orientadora: Kathia Fernandes Lopes Pivetta / Coorientador: Rinaldo César de Paula / Banca: Regina Maria Monteiro de Castilho / Banca: Fabíola Vitti Môro / Mestre

Made available in DSpace on 2014-06-11T19:28:27Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-02-07Bitstream added on 2014-06-13T19:37:02Z : No. of bitstreams: 1 pimenta_rs_me_jabo.pdf: 1521186 bytes, checksum: cffefd90bba68374a881222dc8517b61 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Caryota urens (Lam.) Mart., embora muito utilizada, há poucas informações sobre produção de mudas; desta forma, este trabalho teve como objetivo descrever a morfologia do diásporo (semente com o endocarpo aderido) e da plântula, bem como, estudar a interação entre temperatura e reposição de água em diferentes substratos. O delineamento experimental foi o inteiramente casualizado, em esquema fatorial 6 x 3, (seis temperaturas: 20, 25, 30, 35, 20-30 e 25-35°C; fotoperíodo de 12 horas e três reposições de água: areia - 50, 60 e 70%; esfagno e vermiculita - 80, 100 e 120%), com 4 repetições de 20 sementes. Anotou-se a cada dois dias o número de sementes que emitiram o botão germinativo para determinação da porcentagem de germinação e Índice de Velocidade de Germinação. Os dados foram analisados estatisticamente e as médias comparadas pelo Teste de Tukey (5%). As sementes são albuminosas, com endosperma rígido ocupando quase todo o interior do diásporo. O embrião é lateral, periférico e pouco diferenciado. Por meio da abertura de um opérculo circular no endocarpo, emerge o pecíolo cotiledonar que cresce e dilata em sua extremidade, originando a raiz primária e a parte aérea (plúmula), composta pela primeira folha juvenil completa (eófilo) e pinada (com 2 pinas de forma triangular). As temperaturas de 25ºC e 30ºC foram as mais adequadas e ainda, 25-35ºC, em esfagno e areia, independentemente da reposição de água. A porcentagem de germinação não foi influenciada pelas diferentes taxas de reposição de água, independentemente da temperatura. Em vermiculita, a germinação foi mais rápida repondo 100 e 120% de água. / The palm tree Caryota urens (Lam.) Mart. is extensively used but poorly studied. The objective of this work was to describe the disseminule (the seed with endocarp attached to it) morphology and to evaluate the effects of the temperature, water reposition regimes, and types of substratum on seed germination. The experiment was set according to a completely random design in a factorial arrangement by which the seeds were set to germinate in a 12 hour photoperiod under combinations of different temperatures (the constant temperatures of 20, 25, 30, and 35ºC and the alternate temperatures of 20-30 and 25-35ºC) and different water reposition regimes (at 50, 60, and 70% in sand and at 80, 100, and 120%, in sphagnum and vermiculite). Each treatment was replicated 4 times. The number of germinated seeds (germination button) was counted every two days these data being also used to calculate the germination speed index. The seeds were found to be of the albuminous type with a hard endosperm occupying almost the entire inner space of the disseminule. The peripheral embryo occupies a lateral position and is little differentiated. The cotyledonous petiole emerges through a circular operculum in the endocarp, grows and enlarges its extremity, from which the aerial part (plumule) and the primary root are originated. The plumule is formed by the first juvenile complete bipinnate leaf (the eophylle, with two triangular leaves which gives them a tail fin appearance). In any of the used substrata the temperatures of 25 and 30ºC were the best for the germination of seeds; for sphagnum or sand, independently of the water reposition regime, temperatures of 25-35ºC too gave good results. Seed germination percentage was not affected by the different water reposition regimes independently of temperature. In vermiculite, germination is faster when water reposition takes place at 100 and 120%.

A portable infra red gas analyzer was used to investigate the interactive effects of light, temperature, and CO,jO, ratios under controlled environmental conditions in an attempt to model gas exchange characteristics of Coix Iachryma-jobi L. Plotting light response curves as a function of temperature (20, 25 30 and 35°C) revealed no sign of light saturation even at a photosynthetic photon flux density (PPFD) close to 2000 !Lmol m-' sol. High net assimilation rates (A) of approximately 24 !Lmol CO, m"s'! were realized at 30-35°C. Assimilation (A) versus internal CO, partial pressure (C,) curves showed a steep rise with increase in C, but saturated at approximately 150 (JLII-!) and all the results, either in the absence or presence of 0" showed a similar response under all temperature regimes. C. Iachryma-jobi exhibited low CO, compensation points cr ) between 0 and 10 JLlI-! under similar experimental temperatures and either at 0 or 21%0,. The slopes of double reciprocal plots of llA versus llCi, were nearly identical and crossed the yintercept at almost identical points under all 0, concentrations. These data indicate first; that there was no apparent 0, inhibition and second; indicated that the apparent inhIbitor constant (K,) for 0, at the site of carboxylation did not change with increase in [OJ from 0 to 21% oxygen. These observations were further confirmed by results obtained from the analysis of apparent carboxylation efficiency (CE, as defined as the slope of response of A to increasing CO,), as no inhibition of A with increase of [OJ occurred. These characteristics were consistent with typical features of C,photosynthesis. The absence of 0, inhibition and low r values indicated that an efficient CO, concentrating mechanism which eliminates photorespiration exists in C. Iachryma-jobi. At the light microscope level, leaf anatomy exhibited typical C, structure viz. bundle sheath with large chloroplasts and this sheath is further surrounded by a radiate Kranz mesophyU cells. Furthermore the anatomical features suggested that C. wchryma-jobi was an NADP-ME species. Stomatal conductance (g,) to assimilation (g,/A) indicated an increase in A with decrease in g" an essential feature of improving water use efficiency (WUE), but one which drastically reduces CO, diffusion rate. The physical lintitation (stomatal lintitation, t) to CO, diffusion under various [0,] and temperatures, but constant PPFD, did not exhibit statistically significant change in t values at either 0 or 21% a, within each temperature regime, however there was a marked decrease in t as the plant approached its optimum photosynthetic temperature.

No description available.

No description available.

Pure cultures of Saprolegnia ferax (Gruith) Thuret, Achlya americana Humphrey, and two isolates of Saprolegnia parasitica Coker were grown in a chemically defined medium under controlled conditions of temperature and illumination. Light inhibited growth and oogonium formation rates in S. ferax and A. americana. Light inhibited zoospore germination rates in A. americana and the growth rate of S. parasitica isolate 2-27-59; S. parasitica isolate 6-28-60 was indifferent to light. Neither isolate of S. parasitica formed sexual structures during the experiments. Differences in light reactions and growth rates of these two isolates indicated physiological strain differences. Photoreactivation was demonstrated in S. ferax and both isolates of S. parasitica. Evidence was shown that light caused production of toxic substances in the medium which caused inhibition of growth and sporulation. The blue peroxychromic test for hydrogen peroxide in the medium was negative but apparent catalase activity was demonstrated. Using a simple medium consisting of glucose, soluble starch and yeast extract, white light stimulated vegetative growth in S. ferax and A. americana. A quantitative distribution pattern of oogonium formation was shown. / Ph. D.

Responses of day-neutral (DN) strawberries (Fragaria X ananassa Duch.) to photoperiod and temperature under controlled environment conditions were studied and compared to those of Junebearers (JB) and everbearers (EB). At a constant 21°C, DN cultivars flowered under 9 hour days (SD), night interrupted SD (NI) and 16 hour days (LD). Runner production occurred under NI and LD but not SD. Net photosynthesis (Pn) expressed on a leaf area basis, tended to be higher for DN than JB or EB. Pn on a whole plant basis, was greater under NI than SD due to increased leaf area under NI. Pn under LD was not considered. Under fluctuating temperatures (18°/14°, 22°/18°, 26°/22° or 30°/26° C day/night combinations), responses to SD and NI varied. At 18/14, DN cultivars flowered under either NI or SD. At 22/18 and 26/22, flowering was greater under NI than SD. At 30/26, flowering did not occur. At 18/14, 22/18, or 30/26, runner production was unaffected by photoperiod and occurred under NI and SD. At 26/22, runner production was enhanced by NI compared to SD. Data for the Junebearers and everbearers is also presented and discussed. / Master of Science

The effects of high medium temperatures on the growth and mineral nutrition of selected woody plants and on the composition of the medium solution were studied. Medium temperature profiles were established for 3.8-liter black polyethylene containers exposed to solar radiation under Virginia nursery conditions. On clear days in mid-summer, maximum recorded medium temperatures on the southwest side of containers were as high as 45°C and could exceed 40°C for 4 to 5 hours. The high medium temperatures in exposed containers reduced the shoot relative growth rate and the specific rate of nitrogen uptake for Ilex crenata ‘Convexa’ in comparison to that of plants grown in containers insulated from solar radiation. Shoot dry weights of J. crenata ‘Helleri’ , Juniperus chinensis, Buxus microphylla, and Nandina domestica were at least 20% lower in exposed containers than in insulated containers. In a pine bark medium, growth response of J. crenata, J. horizontalis, or N. domestica to increased N application rate was similar when root-zones were at 40°C for 6 hrs/day or more optimal growth temperature. In unlimed pine bark, root-zone temperature of 40°C for 6 hrs/day resulted in higher medium solution pH and NH₄- N:NO₃-N ratio than at lower temperature. Limestone addition to the medium negated these effects and alleviated growth reductions due to high root-zone temperature for N. domestica and J. horizontalis. The higher medium solution pH associated with heated root-zones resulted in lower medium solution and shoot tissue Mn concentrations for I. crenata. A limed pine bark medium periodically fertilized with ammonium N was heated to temperatures of 28°, 34°, 40°, 46°, or 52°C for daily exposure duration of 1, 2, 4, 6, or 24 hours for 20 days. Treatment temperature of at least 40°C with a daily exposure duration of 24 hours resulted in an increase in medium solution NH₄-N concentration. Similar increase in NH₄-N was found for 2 hr/day exposure to 46°C, with further increases in NH₄-N at longer exposure times. The maximum level of NH₄- N occurred after 1 hr/day exposure to 52°C or 24 hr/day exposure to 46°C. Decreases in medium solution NO₃-N concentration generally coincided with the increases in NH₄- N. Results indicate that high container temperature may increase the ratio of NH₄- N:NO₃-N in the medium solution of plants fertilized with predominately ammoniacal N. / Ph. D.

Sugarcane plants (cultivar NCo376) were studied to assess the effects of temperature and season (spring and autumn equinox) on the morphological and physiological response of stalk components. Plants were grown from single-eyed setts for ca. five months and then placed into three temperature controlled glasshouses (22/12°C (C), 27/17°C (W) and 32/22°C (H) day/night temperatures). The plants were sampled twice weekly over a one month period., and intemodes 4, 6 and 10 of the primary haulms of each plant sampled for growth and sugar analysis. During spring, the leaf emergence rates were 0.0303, 0.1095 and 0.1682 leaves d(-1) at temperatures C, W and H, respectively; and 0.0327, 0.0824 and 0.113 leaves d(-1) in autumn. The phyllochron intervals were 114°Cd in spring and 147°Cd in autumn. Highest green leaf blade area of the primary haulms was achieved at H (438.0 and 511.7 cm2 in spring and autumn, respectively). The stalk extension rates were 1.22, 1.02, 0.38 cm d(-1) (spring) and 1.35, 0.98, 0.45 cm d(-1) (autumn), respectively, in descending order of temperature. Total biomass and stalk biomass per plant were not affected by temperature, despite the differences in stem elongation. Internodes of plants at C were shorter but thicker and heavier than the comparable internodes of plants at W and H. In autumn, the mature internode sucrose concentrations were 35.5, 29.2 and 25.5% at C, W and H, respectively; corresponding to mean RS% of 5.7, 9.8 and 13.3%, and fibre % of 58.8, 61.1 and 61.3%, at the respective ascending order of temperature. Sucrose % in the mature internodes in spring were 27.8, 20.9 and 19.9% at C, W and H, respectively; corresponding to RS% of 5.9, 9.76 and 10.9% and fibre % of 66.3, 69.4 and 69.2% at the respective ascending order of temperature. Temperature effect on the concentration of the stalk components of the immature internodes was in general not significant. Sucrose partitioning coefficients in the mature internodes were 0.25, 0.21 and 0.20 in spring and 0.50, 0.32 and 0.21 in autumn (at C, W and H, respectively). Data that resulted from this study, which is isolated to temperature and cultivar NCo376 can be used in models of sugarcane that simulate leaf appearance and senescence, assimilate partitioning between leaf and stalk and assimilate partitioning between the stalk components namely sucrose, reducing sugars and fibre. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2005.