The objective of this study was to determine how the rice plant responds to combinations of temperature and photoperiod. Both temperature and photoperiod are important for normal completion of the life cycle, but there has been little study of their combined effects in rice. Controlled temperature and photoperiod experiments were conducted in growth cabinets using 4 temperatures; 35/18, 35/26.5, 35/35 and 40.5/18°C day/night. There were 4 photoperiods of 8, 10, 12 and 14 hours. Light was provided by cool white fluorescent tubes. The day temperature periods corresponded to the photoperiods. Four varieties were selected: Kangni-27 and Dokribasmati from Dokri, Pakistan; Caloro from California, U.S.A.; and Bluebonnet-50 from Texas, U.S.A. Growth characteristics, net photosynthesis rates, and flowering were measured and chlorophyll a and b, carotenoid, carbohydrate and ash concentrations were determined. The effect of photoperiod on flowering was most pronounced at 35/26.5. The delays in flowering at 14 hours for this temperature were 30, 30, 21 and 63 days in Kangni, Caloro, Dokri and Bluebonnet compared to the optimum, photoperiod which varied among varieties. The delays observed at 35/18 were 23, 14, 6 and 2 days. At 35/26.5 all varieties showed a significant photoperiodic effect on flowering, but at 35/18, Dokri and Bluebonnet did not show a significant photoperiodic effect. 35/35 was most unsatisfactory for flowering. A similar but less serious effect was found at 40.5/18. Final dry matter production was high at 35/35 and 40.5/18; an increase of 3 to 8 g per pot was noted at these temperatures compared with 35/26.5 and 35/18. There was an increase of about 5 g per pot at maturity for each increase of 2 hours in photoperiod. Panicle characteristics were generally unaffected by temperature, but there were some photoperiod effects. At the 12-hour photoperiod panicles of all varieties were 2 to 4 cm longer than at other photoperiods and at 10-and 12-hour photoperiods there were 10 to 32 more spikelets per panicle than at 8 and 14 hours. Sterility was very high at 35/35 (95%) and 40.5/18 (69%). Average sterility at 35/18 and 35/26.5 was about 36%. There was 8 to 24% less sterility at 10- and 12-hour photoperiod compared with 8 or 14 hours. Hundred-grain weight was unaffected by photoperiod or temperature. High numbers of tillers were consistently observed at 40.5/18 and 35/18 and low numbers at 35/35. The differences varied with the stage of growth. Plants at 14-hour photoperiod had consistently more tillers than those at other photoperiods. Kangni and Dokri had higher numbers of tillers than Caloro and Bluebonnet. Leaf development was fastest at 40.5/18 and the 12-hour photoperiod. This was especially so at 6 and 8 weeks. Kangni and Dokri had faster development than Caloro and Bluebonnet. Plant height was 2 to 5 cm greater at 2 weeks at 35/26.5 and 35/35 but at 4, 6 and 8 weeks, plant height was greater at 35/18. The shortest plants were observed at 40.5/18. The rate of net photosynthesis on a leaf blade weight basis was highest at 2 weeks in all varieties at all photoperiods and temperatures. The rate generally declined with the aging of plants. The greatest decline at 8 weeks, compared to 2 weeks, was 71% in Dokri and least was 65% in Bluebonnet. Except at 2 weeks, the highest rate of photosynthesis was at 40.5/18 but at 6 and 8 weeks there were also high rates at 35/35. The rate was consistently higher in plants growing in the 8-hour photoperiod. The rate was higher in the 8-hour photoperiod compared to the 14-hour by 28 and 25% at 6 and 8 weeks respectively. Both Caloro and Bluebonnet had higher net photosynthetic rates than Kangni and Dokri. In all varieties chlorophyll and carotenoid content declined with age. Both chlorophyll and carotenoid were high at 40.5/18 at all stages. Chlorophyll concentration was also high at 35/18 at 2, 4 and 6 weeks. A definite correlation between chlorophyll content and photosynthesis was not shown, but there was a significant correlation between chlorophyll and fresh weight at all temperatures and photoperiods except at 2 weeks. Total water soluble carbohydrate and total ash content did not show definite trends according to stages of growth. No relationship could be shown between floral initiation and combined carbohydrate and ash content. / Land and Food Systems, Faculty of / Graduate

Six varieties of rice, representative of those cultivated in California and other southern regions of the United States were grown in a series of nine experiments. In a greenhouse, seeds were sown into pots placed in a constant temperature water bath possessing compartments maintained at water temperatures of 60°, 75°, 60° and 90°F. Many characteristics of plant growth and development were influenced by water temperature. Generally shoot lengths and weights, root lengths and weights, leaf lamina, leaf sheath lengths and stomata number were greater at the higher, than at the lower, temperatures. The type and intensity of silica crystal formation in the leaves increased with increase in temperature. Stomata sizes were larger at lower, than at higher, temperatures. Irrespective of plants being submerged or non-submerged, at continuous or changed temperatures, the higher temperatures produced the greatest response. Californian varieties were found to be more sensitive than other southern varieties in their response to both low and high temperature treatments, indicating a greater range of adaptability. / Land and Food Systems, Faculty of / Graduate

This study of some common turf weeds of the Vancouver area considers some aspects of biology and control. Seed production observations indicated that seeds ranging from 300 to over 260,000 per plant were produced each season by different species. Seeds of Senecio vulgaris L., Sonchus oleraceus L. and Hypochaeris radicata L. germinated immediately after harvest while others required several months. H. radicata showed good germination in light while Cerastium vulgatum L. and Lamium amplexicaule L. germinated best in a shaded or dark environment. Two germination peaks in spring and fall occur in this group of turf weeds. However Stellaria media (L.) Cyrill produced flowers and seed for most of the year. Rumex acetosella L. also had a long flowering period as did Plantago lanceolata L. and P. major L. The three latter species were found to require a long time to mature in the flower head and so were not shedding seed over the considerable period of time characteristic of S. media. Leaf area development did not appear to be associated with root development in the seedling weeds examined, and variations in the relative leaf areas of the different species occurred with time. Marked differences in flowering period and characteristics were apparent in observations on the various weeds made over a 17 month period. Apomictic seeds of Taraxacum officinale L. were found to have a germination rate significantly lower than those produced by artificial pollination. Inhibitory materials present in leaves and stems of weeds were shown to delay germination of bent grass nearly three weeks and to definitely reduce the percentage germination. The species showing the greatest inhibitory properties were Matricaria matricarioides (Less.) Porter, S. media and P. lanceolata in that order. Four turf grasses were shown to differ in their responses to proprietory mixtures of the phenoxy type herbicides, and weed species similarly differed in their responses to the newer herbicides which included Banvel D (dicamba), Tordon, phenoxypropionic materials and mixtures containing two and three chemicals. / Land and Food Systems, Faculty of / Graduate

The effects of temperature and sulphur nutrition on the growth, yield and mineral composition (N, NO₃-N, S and SO₄-S) of Hordeum vulgare L. cv Olli, Pisum sativum L. cv Dark Skin Perfection and Brassica campestris L. cv Arlo, were investigated in controlled environments. The net CO₂ exchange rates and compensation points were also determined at two S levels (0 and 64 ppm) under various temperature regimes. When barley and rape plants were grown at 0 ppm S, deficiency symptoms developed in about two weeks, whereas pea plants at the same level developed deficiency symptoms in about three weeks. Plants at the lowest S level and the highest temperature took the shortest time to develop S deficiency symptoms. Fresh and dry weights, shoot length, number of nodes and number of fertile fruit increased with increasing S levels. Shoot growth in all three species was more depressed by S deficiency than root growth. Optimum growing temperature regimes for barley and peas were found to be 24/16 at the vegetative stage and 18/10°C at the mature stage as evident from increased weights, maximum fruit set and mineral uptake. Optimum temperature for rape plants was 29/21°C at both stages of growth. Detrimental effects of cotyledon or endosperm removal tended to mask the effects of temperature and S levels. This method was thus found to be unsatisfactory for the study of S nutrition in plants. Higher mineral concentration was observed at the vegetative stage than at the mature stage in peas and rape plants, while in barley the mineral concentration remained constant at both stages of growth. With increase in S supply there was an increase in uptake of both total S and SO₄-S. Uptake also increased with increasing temperatures. This increase was largely due to "concentration effects". Hence the use of SO₄-S level as a criterion for diagnosis of S deficiency may be unsatisfactory, unless plants are grown at optimum temperatures. S deficient plants had increased total N and NO₃-N concentrations in all three species. NO₃-N concentration also increased with an increase in temperature. The total N concentration did not increase appreciably with temperature. Consequently, at low S level (0 and 8 ppm) total N:total S ratios (N:S) tended to increase or decrease depending on low or high growing temperatures respectively. These changes in ratios were independent of actual size of the plants. Furthermore the ratios for all S levels at the vegetative stage were lower than those at the mature stage. Therefore both temperature and stage of growth are important factors to be considered in interpreting S deficiency from N:S ratios in plants. The net C0₂ exchange rates were generally higher at 20 days than at 30 days. At 0 ppm S level and at high temperature, the decline in net C0₂ exchange rate with age was greater. Maximum CO₂ exchange rates were observed at the optimum growing temperatures for both S levels. Increasing the measuring temperature above the growing temperature caused no further stimulation in CO₂ uptake, and at high temperatures there was a decrease in uptake. When CO₂ exchange rates were measured at two 5.5°C intervals above and below the growing temperatures the maximum rates were recorded at or below growing temperatures in all the species at both S levels. The CO₂ compensation values were higher with lower S level in the leaf tissue than at higher S levels. Increase in growing temperatures also caused larger CO₂ compensation values than at lower temperatures. Negative correlations between CO₂ compensation point and leaf tissue S level and positive correlations between CO₂ compensation point and temperature were observed in barley and peas. / Land and Food Systems, Faculty of / Graduate

Call number: LD2668 .T4 1934 N31 / Master of Science

Call number: LD2668 .T4 1985 X56 / Master of Science

Mitochondria were extracted from seedling radicles of Pima S-5 and Pima E-14 cottons and the state 3 respiration, state 4 respiration, ADP:O ratio and respiratory control (RC) ratio were measured in vitro over a range of temperatures from 6 to 18C. Mitochondria from E-14 seedlings exhibited a mean state 3 respiration rate of 13.42 μMO₂/min/gm tissue while mitochondria from S-5 seedlings showed a mean state 3 rate of 17.94 μMO₂/min/gm tissue. Mean state 4 respiration exhibited a similar trend with measurements of 73.4 μMO₂/min/gm tissue and 11.73 μMO₂/min/gm tissue for E-14 and S-5. Mitochondria from E-14 seedlings exhibited a mean ADP:O ratio of 3.73 compared to an ADP:O of 3.28 for S-5, across all assay temperatures. Mean respiratory control ratio was 1.79 for E-14 and 1.53 for S-5. These lower respiration rates of E-14 coupled with higher ADP:O ratios and RC ratios support a greater respiratory efficiency at low temperatures of this variety compared to S-5. Additionally, the E-14 mitochondrial membranes exhibited an ability to remain in a fluid state to a lower temperature than Pima S-5 mitochondrial membranes as judged by Arrhenius plots of respiration. Since mitochondrial respiration is considered to be regulated by membrane-bound enzymes, any change in membrane fluidity would conceivably affect mitochondrial enzyme activity and thus alter respiration rates. Changes in respiration rates will be reflected as a break in an Arrhenius plot. The mean break point temperature of state 3 respiration was 10.7C for E-14 and 13.4C for S-5. The mean break point temperature for state 4 respiration was 10.9C for E-14 and 13.6C for S-5. The ability of E-14 to withstand a greater degree of chilling under field conditions can be attributed, in part, to the greater fluidity of seedling mitochondrial membranes at low temperatures and concomitant conservation of respiratory energy through a lower rate of respiration. Assays of mitochondrial respiration and Arrhenius plots of mitochondrial respiration versus temperatures could be used to select cotton lines more tolerant to chilling temperatures.

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The hydraulic conductance of a plant is a significant factor in determining the / Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2008.

Orientador: Maurício Dutra Zanotto / Banca: Sérgio Gonçalves Dutra / Banca: Tiago Zoz / Banca: Marcelo de Almeida Silva / Banca: João Paulo Teixeira Whitaker / Resumo: O óleo da mamona (Ricinus communis) possuí inúmeras aplicações na área industrial e na produção de biodiesel, demonstrando assim sua importância econômica. O Brasil é o quarto maior produtor mundial de óleo de mamona com grande potencial para ser protagonista na produção de mamona, sendo a utilização de híbridos uma alternativa para tal fim, contudo existe dificuldade da obtenção devido às variações climáticas. Assim, o presente trabalho teve por objetivo a construção de uma câmara de crescimento, para simular diversas condições climáticas para auxiliar na seleção de plantas, além de utilizar essa câmara de crescimento para avaliar o efeito isolado da alta temperatura na reversão sexual da mamona. Para criação da câmara de crescimento foram utilizadas lâmpadas, ar condicionado, aquecedores e sensores; além de um Arduino Mega 2560 R3, que controla todo o sistema. Durante esse experimento, foram feitas avaliações quanto à intensidade luminosa requerida para o total desenvolvimento das plantas de mamona. Nessa mesma câmara de crescimento, foi realizado o experimento do efeito isolado da alta temperatura com relação à taxa de flores masculinas e femininas no híbrido FCA 2007-1 e na reversão sexual sobre as fêmeas MRZ 14. O delineamento experimental utilizado para avaliar a taxa de flores entre masculina e feminina do híbrido FCA 2007-1 foi de blocos ao acaso, em parcelas subdivididas com três repetições. As parcelas foram constituídas pelo número de dias após a emergência em que ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Castor oil (Ricinus communis) is present in many industrial applications and in the production of biodiesel, demonstrating its economic importance. Brazil is the fourth largest castor oil producer in the world with great potential to be a protagonist of castor bean, and the use of hybrids is an alternative for this purpose, however there is difficulty in obtaining it due to climatic variations. So, the aim of the present work was the construction of a growth chamber, in which it simulates various climatic conditions to aid in the selection of plants, besides using this growth chamber to evaluate the isolated effect of high temperature on the castor's sexual reversion. To create the growth chamber were used lamps, air conditioning, heaters and sensors; plus, an Arduino Mega 2560 R3, which controls the entire system. During this experiment, evaluations were made to know how much light intensity is required for the full development of castor bean plants. In this same growth chamber, the isolated high temperature effect experiment was performed in relation to male and female flowers rate in the FCA 2007-1 hybrid and in the sexual reversion on MRZ females 14. The experimental design used to evaluate the flower rate between male and female in the FCA 2007-1 hybrid was a randomized block design with split-plots with three replicates. The plots consisted of the days after the emergence of the plants, when the high temperature stress (14, 21, 28 and 35 days) was started, and the sub-p... (Complete abstract click electronic access below) / Doutor