The role of light and temperature on flowering of South African Watsonia species were evaluated to assess the potential for this genus as a commercial flower crop. Species were selected that represent different climatic regions of South Africa, with the aim of understanding how ecologically distinct species perform under cultivation. The four selected species were W. borbonica and W. tabularis (winter-rainfall area), W. angusta (shared rainfall) and W. pillansii (summer-rainfall area). In order to establish the optimum temperature required for flowering, plants were exposed for 12 weeks to three temperature regimes (12/7 °C, 21/15 °C and 29/21 °C) after attaining their first and/or second leaves. A temperature shift of 12/7 °C was used to assess if the plants had a vemalisation requirement. Controls were maintained under 25 % shade under natural conditions, with an average temperature of 24/7 °C. An elevated temperature of 29/21 °C was detrimental to plant growth. Moderate temperatures of 21/15 °C significantly (P<0.001) increased the height and the number of leaves produced per plant relative to the 12/7 °C treatment. These temperatures significantly (P<0.001) increased the total number of flowers produced per plant compared to low temperatures. However, flowering percentage and quality of flowers were reduced. A low temperature regime of 12/7 °C was efficient in satisfying vernalisation requirements and inducing flowering in four selected species. However, the total number of leaves produced per plant was signifcantly reduced. The summer-rainfall species, W pillansii, displayed a qualitative response to vernalisation, as no flowering was observed in non-vernalised plants. Two winter-rainfall species, W borbonica and W. tabularis, demonstrated a quantitative response to vernalisation. These species flowered at non-vernalising temperatures. W angusta behaved like the winter-rainfall species in terms of flowering. Overall, a vernalisaton treatment marginally reduced days to flower while flowering percentage was increased compared to other temperature regimes. However, there was no increase in the total number of flowers produced per plant. Low temperatures were not only effective for flower induction, but also for releasing corm dormancy, thus synchronising growth. Storing corms at either 4 or 10 QC resulted in 100 % sprouting within 4-6 weeks. The role of daylength in flowering of Watsonia plants was established by subjecting plants to long days (LO) of 16 h light and 8 h dark and to short days (SO) of 8 h light and 16 h dark. The number of leaves and flowering were significantly (P<0.01) promoted under the LO regime. However, there was strong temperature and daylength interaction in terms of flowering potential, as at low temperatures flowering was induced irrespective of daylength. In W. pillansii, flowering was obtained under both regimes (LO and SO) applied at the second leaf stage. Flowering in W. borbonica and W. tabularis was only observed under the LO regime at the second leaf stage. In both species, flowering was also obtained in SD-treated plants, provided treatment occurred after the formation of the third leaf. However, the total number and quality of flowers were reduced. To examine the effect of light intensity on flowering, plants at different developmental stages (first and/or second or beyond the third leaf stage) were exposed to photosynthetically active radiation (PAR) of 150 jJmol m-2s-1 or 39.5 jJmol m-2s-1 for 7 weeks. Exposure to low light intensity at either developmental stage compromised leaf quality. No flowering was observed following low light intensity treatment during the first to third leaf stages, even though plants were exposed to low temperature and LO regimes, both of which promoted flowering. Observation of the shoot apical meristem revealed that the second leaf stage was critical as the anatomical transition to flowering occurred at this level. When beyond the third leaf stage, low light intensity did not prevent flowering. However, the number of flowers produced per plant was reduced compared to plants maintained at 150 jJmol m-2s-1. Thus, light intensity played a role in both plant morphogenesis and flowering. LDs were effective in promoting vegetative growth whereas high light intensity and low temperature regimes played pivotal roles in flower induction. This makes them useful horticulture tools to produce desirable Watsonia plants for commercialisation. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2006.

Please read the abstract in the section 00front of this document / Dissertation (MSc)--University of Pretoria, 2005. / Zoology and Entomology / Unrestricted

The Atlantic salmon (Salmo salar) lifecycle is punctuated by distinct ontogenic stages which are routinely manipulated commercially by photoperiod regimes to enable year-round production. As such, light plays a critical role throughout the production cycle, however, it remains poorly characterised and light spectrum and intensity have not been defined optimally yet. This thesis was therefore set out to test the effects of narrow bandwidth light (Blue-&lambda;(max) 444 nm, Green-&lambda;(max) 523 nm, Red-&lambda;(max) 632 nm and White) and intensity in freshwater (FW). Fry-parr development, out-of-season smoltification and ocular and vertebral health were examined as was the long-term effects of FW light regimes on seawater (SW) growth and muscle structure. In addition, the impact of photoperiod regimes on out-of-season smolts following transfer to SW was investigated. &NewLine; Major findings from the trials conducted show that light spectrum and intensity influence parr development with lower intensities performing better than higher intensities. Both the initiation and duration of smoltification was impacted by spectrum. Importantly, this doctoral work showed that daily changes in light intensity, from low during the scotophase to high during the photophase applied for the duration of a standard out-of-season smoltification regime was capable of providing a sufficient cue for the induction of smoltification. Historic FW light exposure impacted SW performance and post-transfer SW photoperiod had significant impact upon growth and maturation development. Results based on changes to the gonadosomatic index provide important guidance for suitable post-transfer photoperiods for smolt transferred to SW around the winter solstice. Importantly, from the parameters tested, exposure to different spectrum or light intensities did not adversely affect vertebral or ocular health. &NewLine; This thesis did not only focus on the physiological effects of light but also aimed to characterise better the pathways involved in light perception and integration. To do so, the neural response to both broad spectrum white light, darkness and Red and Blue light was investigated through deep brain insitu-hybridisation and high throughput sequencing (NGS) of the pituitary gland. Results showed substantial spectral and light/dark changes in the both the deep brain and pituitary transcriptome. Overall, this research provides both scientifically interesting and commercially relevant guidance for the optimisation of lighting systems for use in captive salmon aquaculture. Major findings from the trials conducted show that light spectrum and intensity influence parr development with lower intensities performing better than higher intensities. Both the initiation and duration of smoltification was impacted by spectrum. Importantly, this doctoral work showed that daily changes in light intensity, from low during the scotophase to high during the photophase applied for the duration of a standard out-of-season smoltification regime was capable of providing a sufficient cue for the induction of smoltification. Historic FW light exposure impacted SW performance and post-transfer SW photoperiod had significant impact upon growth and maturation development. Results based on changes to the gonadosomatic index provide important guidance for suitable post-transfer photoperiods for smolt transferred to SW around the winter solstice. Importantly, from the parameters tested, exposure to different spectrum or light intensities did not adversely affect vertebral or ocular health. This thesis did not only focus on the physiological effects of light but also aimed to characterise better the pathways involved in light perception and integration. To do so, the neural response to both broad spectrum white light, darkness and Red and Blue light was investigated through deep brain insitu-hybridisation and high throughput sequencing (NGS) of the pituitary gland. Results showed substantial spectral and light/ dark changes in the both the deep brain and pituitary transcriptome. Overall, this research provides both scientifically interesting and commercially relevant guidance for the optimisation of lighting systems for use in captive salmon aquaculture.

Paralelamente ao modelo Arabidopsis thaliana, o tomateiro (Lycopersicon esculentum) tem sido crescentemente utilizados em abordagens genéticas de questões fisiológicas. Uma das principais vantagens de Arabidopsis como "planta de laboratório" tem sido seu pequeno porte e ciclo de vida curto. Contudo, a cultivar Micro-Tom (MT) de tomateiro possui tamanho muito reduzido (8 cm) e pode produzir até 5 gerações por ano. Mutantes fotomorfogenéticos em tomateiro deficientes na síntese do cromóforo do fitocromo (au), mutantes deficientes na síntese das apoproteínas PHYA e PHYB1 (fri e tri, respectivamente) e mutantes superexpressando o fitocromo (hp, atv e Ip) constituem-se em um modelo para estudos da fotomorfogênese. No que se refere à capacidade de regeneração in vitro como uma resposta fotomorfogenética, poucos trabalhos têm sido realizados. O presente trabalho teve como objetivo transferir as mutações au, fri, tri, hp, Ip e atv, bem como o locus de regeneração (Rg1) da cultivar MsK, para a cultivar Micro-Tom. As linhagens obtidas foram utilizadas para verificar o efeito da fotomorfogênese na competência para regeneração in vitro. Para tanto, foram realizados tratamentos com luz branca, vermelho (V) e vermelho-extremo (VE) em explantes radiculares, caulinares e foliares do genótipo micro-MsK em meio MS mais 5mM de BAP e tratamentos com luz branca em explantes radiculares, caulinares e foliares de micro-mutantes fotomorfogenéticos também em meio MS mais 5mM de BAP. Para todos os tratamentos utilizou-se a cultivar MT como controle. Sob V, as raízes de micro-MsK apresentaram-se diferenciadas, enquanto sob VE não ocorreu diferenciação. O maior número de gemas formadas tanto para caule quanto para folhas de micro-MsK ocorreu sob V, enquanto sob VE foi observado um decréscimo na formação de gemas. A partir destes resultados sugere-se que a forma ativa do fitocromo, induzida pelo V, interage com o Rg1 na aquisição de competência para regeneração. Nos tratamentos com luz branca, raízes de micro-MsK e de mutantes micro-hp, micro-atv e micro-Ip apresentaram-se diferenciadas, enquanto não houve diferenciação para o mutante micro-au ou para o controle MT. O número de gemas formadas alcançou maiores valores para folhas de micro-hp e micro-Ip e a para caules de micro-atv. Apenas um número muito reduzido de gemas foi formado a partir de folhas de micro-au. Com base na alta competência para regeneração de micro-MsK e de mutantes que superexpressam o fitocromo, sugere-se que o fitocromo promove, em uma via de sinalização, a indução de fatores de regeneração (Rg1). Alternativamente, o locus Rg1 poderia promover a alta capacidade regenerativa tornando os explantes mais competentes ao efeito da superexpressão do fitocromo, o qual poderia induzir outros fatores de regeneração. / Parallel to Arabidopsis thaliana model, the tomato (Lycopersicon esculentum) has been increasingly used as a genetic approach to address physiological questions. One of the main advantages of Arabidopsis as a "laboratory plant" has been its small size and short life cycle. However, the tomato cultivar Micro-Tom (MT) possesses reduced size (8 cm) and can produce up to 5 generations per year. Tomato photomorphogenic mutants deficient for the synthesis of phytochrome chromophore (au) or the apoprotein PHYA and PHYB1 (fri and tri, respectively), as well as mutants superexpressing phytochrome (hp, atv and Ip) consist on a model to study photomorphogenesis. Concerning the in vitro regeneration capacity as a photomorphogenic response, fewer works have been carried through. The current work aimed at transfering the mutations au, fri, tri, hp, Ip and atv, as well as the regeneration locus (Rg1) of cv MsK to the cv Micro-Tom (MT). The genotypes obtained were used to verify the effect of photomorphogenesis on the competence for in vitro regeneration. Root, stem and leaf explants from MT and Micro-MsK were incubated in MS plus 5mM BAP under white, red (R) and far-red (FR) light. Root, stem and leaf explants from MT and photomorphogenic micro-mutants were incubated in MS plus 5mM BAP under white light. Under R, roots of micro-MsK were presented differentiation, while under FR the differentiation did not occur. Under R, stem explants from micro-MsK formed more shoots than did leaf explants, while under FR was observed a decrease in shoot formation for all types of explants. These results suggest that the active form of phytochrome, induced by R, interacts with the Rg1 in the acquisition of competence for regeneration. In the treatments with white light, roots of micro-MsK and of mutants micro-hp, micro-atv and micro-Ip presented differentiation, while no differentiation was observed for the mutant micron-au or control MT. The number of shoots formed reached the highest values for leaf explants of micro-hp and micro-Ip and for stem explants of micron -atv. Only a low number of shoots was formed from micro-au leaf explants. On the basis of the high competence for regeneration of micro-MsK and mutants that super express phytochrome, it is suggested that the phytochrome promotes, in a signaling pathway, the induction of regeneration factors ( Rg1 ). Alternatively, the Rg1 locus may turn the explant most competent to respond to phytochrome, which could induces others regeneration factors.

Bibliography: leaves 168-187. / viii, a-f, 187, [51] leaves, [12] leaves of plates : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Investigates the environmental control of seasonal reproduction and the role of the pineal in the transmission of multiple environmental signals to the reproductive axis. The principle species studied was the highly seasonal native Australian bush rat, Rattus fuscipes greyi. / Thesis (Ph.D.)--University of Adelaide, Dept. of Obstetrics and Gynaecology, 1994

Includes bibliographical references (leaves 166-195) Addresses the nature of the central mechanisms involved in the regulation of the circadian pattern of secretion of the pineal hormone melatonin in the highly seasonal Suffolk breed of sheep. Provides new information on the behaviour of the onset and offset of melatonin secretion under different photoperiodic conditions.

Patterns of nest attendance behavior by breeding birds represent a parent-offspring trade-off in which adults balance self-maintenance with parental care decisions. Incubation, in particular, is of interest because adults must provide an environment suitable for embryonic development through nest-building and contact-incubation. We evaluated how adult incubation constancy and nest visitation rates varied with life and natural history traits of temperate and tropical bird species. We found that constancy did not differ by latitude or with nest survival rate. A strong negative correlation between incubation constancy and egg mass relative to adult body mass was present. Birds with low constancy tended to have larger relative egg masses and higher basal metabolic rate. Because adult incubation constancy is relatively plastic (i.e., varies with ambient temperature), birds with larger relative eggs may respond to lower cooling rates rather than direct selection for higher or lower constancy. We then assessed if rates of nest visitation (trips to nests by adults during incubation and nestling phases) followed the predictions of the Skutch hypothesis. Skutch suggested that birds nesting in environments with high levels of nest predation would reduce numbers of trips to their nests so as to minimize the risk of visual detection by nest predators. We found support for the basic pattern predicted by Skutch. We also extended his hypothesis to predict other behavior associated with nesting, such as responses of parents to intruders at the nest. Despite apparently early departure from the nest site, adults with higher visitation rates remained conspicuous around the nest site. Thus, while the flight initiation distance from the human observer was earlier than expected, conspicuousness of behavior was associated with nest visitation rate. Finally, we assessed how an environmental variable, photoperiod, might influence rate of embryonic development in a wild songbird, Sylvia atricapilla. We exposed eggs throughout the incubation period to daily photoperiods consisting of 4 hours of light and 20 hours of dark (4L), 12 hours light and 12 hours dark (12L), 20 hours light and 4 hours dark (20L) and a skeleton photoperiod with two 1-hour pulses of light that framed a 20-hour day. We found that the skeleton treatment group differed significantly from our 4L and 12L, but not the 20L treatment groups. The skeleton photoperiod accelerated embryonic development. We suggest that photoperiod may influence incubation period in wild birds and could account for some portion of the widely observed latitudinal variation in incubation period of songbirds. We encourage others to assess how photoperiod interacts with parental attendance patterns to affect embryonic development. / Graduation date: 2013 / Access restricted to the OSU Community at author's request from March 13, 2013 - March 13, 2015

The expression of photorefractoriness, a feature of seasonal breeding in birds, is important in production species, where egg production and fertility are affected by the photoperiod. Years of selection in meat-type birds have reduced the potential reproductive function, and the environmental manipulation of such genotypes is essential to maximise productivity. While it is known that egg-type pullets no longer exhibit photorefractoriness, and that female broiler breeders do, there is not much information about the response of male broiler breeders to photoperiod. Such information is important when designing lighting programmes for breeding stock, and this study aimed to gain more insight into the male response to photoperiod. A series of experiments was designed in order to achieve this. In the first the response of male broiler breeders to rearing on constant photoperiods was measured, and in the second the effects of age at photostimulation on age at sexual maturity were assessed. The response to an increase in photoperiod during the production cycle was investigated in the third trial. Evidence of photorefractoriness in males was observed, but this was not the case in all birds, possibly due to high variation in some of the fertility traits measured. It seems possible that males do not respond to photoperiod to the same extent as females. Unexpected observations of a response in some birds to early photostimulation, and the high variation observed prompted another experiment in which the heritability of the response to early photostimulation was measured as a potentially revolutionary method of selection, whilst checking that this response is not negatively linked to broiler growth rates. Left and right testis weight data, collected in the above experiments, were analysed for asymmetry. There was no consistent response in testes asymmetry to photoperiod, or evidence that asymmetry in testis weights is as a result of the imposition of genetic or environmental stress. The strong correlation found between testes dimensions and weight suggests that predictions of testis weights could be made through ultrasonics or laparoscopy. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2010.

No abstract available. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2008.

Includes bibliographical references (leaves 166-195) / xxi, 195 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Addresses the nature of the central mechanisms involved in the regulation of the circadian pattern of secretion of the pineal hormone melatonin in the highly seasonal Suffolk breed of sheep. Provides new information on the behaviour of the onset and offset of melatonin secretion under different photoperiodic conditions. / Thesis (Ph.D.)--University of Adelaide, Dept. of Animal Sciences, 1991?