Photoperiod studies have been the subject of research projects for decades. In such studies, Rudbeckia hirta L. has often been chosen due to its early recognition (1920?s) as a long day plant. R. hirta has also been the subject of experiments to evaluate the timing of floral initiation in regard to the exogenous application of phytohormones. Former projects have been primarily directed toward understanding floral initiation mechanisms of long day plants for the production of greenhouse grown crops. Photoperiod manipulation and exogenous application of phytohormones have not been used to the same extent for field-grown fresh flower research. Three experiments were conducted in the spring of 2006 to determine if time to flowering could be manipulated for field grown R. hirta without subsequent loss of quality. In the first experiment, two cultivars, R. hirta ?Indian Summer? and R. hirta ?Irish Eyes? were given 4-hour night interruption (NI) using a 60-watt incandescent bulb during greenhouse production. Night interruption lasted for 0, 21, 28 or 35 days. Prior to field transplanting, GA3 was exogenously applied once to transplants at rates of 0, 150 or 300 ppm. For ?Indian Summer?, early flowering was achieved with 35 days of NI alone or with either rate of GA3 plus 21-day NI. Increasing GA3 to 300 ppm improved stem length. For ?Irish Eyes?, 35-day NI alone was equally effective at producing early blooms compared to 35-day NI and either rate of GA3. The second experiment included R. hirta ?Irish Spring? grown in the greenhouse then given 0 or 35 days NI as in the first experiment. Then, seedlings were transplanted to the field in plots with various combinations of polyethylene row cover, black plastic mulch and bare ground. Only plants receiving 35-day NI flowered during the test. Polyethylene row cover increased the percentage of blooms harvested. The third experiment measured the vase life of blooms harvested from experiments one and two. Treatments did not affect vase life of blooms. Mean post harvest life for all treatments was greater than 7 days.

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Grasslands account for almost one quarter of the world’s cover of vegetation. Almost three quarter of the world’s milk, beef and veal are produced from temperate grasslands. In New Zealand, ryegrass (Lolium perenne) is the main pasture constituent with more than half of the total export revenue coming from grass-related products. Much of ryegrass production and quality depends on the timing of flowering through seasonal progression. In many plants, day length is the critical environmental parameter that controls when plants begin to flower. In Arabidopsis the CONSTANS (CO) gene mediates day length response. Upstream of CO is the GIGANTEA (GI) gene which is associated with the circadian clock mechanism and is required to promote CO expression. The FT gene is the immediate downstream genetic target of CO and is a direct promoter of flowering. In this study, cDNA libraries, sequence alignment and genome walking were used to sequence and describe three putative orthologues from the ryegrass photoperiod pathway: LpGI, LpCOL1, and LpFT3. All three behaved in a true photoperiod manner characterised by cycling expression patterns under continuous light conditions and differential expression patterns in LD and SD conditions. Different photoperiods brought about differences in expression of these genes measured either by the phase shift change (LpGI and LpCOL1) or by the change of the transcript level (LpFT3). Gene expression changes over a vernalisaton time course were also analysed and results indicated that LpFT3 acts as the flowering integrator. The role of LpGI, LpCOL1, and LpFT3 as putative photoperiod genes was further confirmed by genetic mapping, which placed them on linkage groups 3, 6, and 7, respectively. The syntenic positions in rice contain major heading date quantitative trait loci. The function of LpFT3 was examined by over-expressing the gene in Arabidopsis under control of the cauliflower mosiac virus (CaMV) 35S promoter. Substantially higher expression of the endogenous Arabidopsis AtFT transcript was observed in the mutated ft-1 line overexpressing LpFT3, suggesting a positive feedback loop either directly or through upstream intermediaries. Overexpression of the LpGI and LpFT3 genes restored rapid flowering to the respective gi-3 and ft-1 Arabidopsis mutants while overexpression of LpCOL1 did not accelerate flowering either in co-2 or wild type Arabidopsis plants. However, overexpression of LpCOL1 completely restored the late flowering phenotype of the gi-3 mutant indicating the existence of another important link outside the well established hierarchy of GI-CO-FT in the photoperiod pathway. This study revealed that the ryegrass photoperiod pathway genes show high similarity to their wheat, rice and Arabidopsis counterparts. Exploring ways to modulate flowering time in ryegrass could provide major benefits to the agricultural industry by increasing forage quality, controlling seed and pollen production, and addressing potential problems linked with climate change.

Abstract Reproductive performance of experimental commercial Dalland sows (n = 87) maintained under a constant photoperiod (10 h light and 14 h darkness) and control sows (n = 187) maintained under natural daylight length (10.4 h light in winter and 13.4 h light in summer) were compared. In early summer 4.1% of experimental sows returned to oestrus compared to 20.8% of the control sows. In late summer 9.1% of experimental sows returned to oestrus compared to 21.9% of the control sows. Reduced photoperiod improved the farrowing rate of experimental sows in the early summer breeding compared to the control group (95.4% and 81.3%, respectively). With winter breeding there was a small proportion of sows that returned to service in both groups (7.9% and 8.9%) while the farrowing rate was high in both groups (93.9% and 91.0% in the experimental and control groups, respectively). Litter sizes derived from early summer services were 11.4 and 11.6 for the experimental and control groups, respectively, while winter services led to litter sizes of 11.6 and 12.4 whereas in late summer services, regulated photoperiod had improved the litter size of the experimental group (12.3) compared to the control group (11.2).

Grasslands account for almost one quarter of the world’s cover of vegetation. Almost three quarter of the world’s milk, beef and veal are produced from temperate grasslands. In New Zealand, ryegrass (Lolium perenne) is the main pasture constituent with more than half of the total export revenue coming from grass-related products. Much of ryegrass production and quality depends on the timing of flowering through seasonal progression. In many plants, day length is the critical environmental parameter that controls when plants begin to flower. In Arabidopsis the CONSTANS (CO) gene mediates day length response. Upstream of CO is the GIGANTEA (GI) gene which is associated with the circadian clock mechanism and is required to promote CO expression. The FT gene is the immediate downstream genetic target of CO and is a direct promoter of flowering. In this study, cDNA libraries, sequence alignment and genome walking were used to sequence and describe three putative orthologues from the ryegrass photoperiod pathway: LpGI, LpCOL1, and LpFT3. All three behaved in a true photoperiod manner characterised by cycling expression patterns under continuous light conditions and differential expression patterns in LD and SD conditions. Different photoperiods brought about differences in expression of these genes measured either by the phase shift change (LpGI and LpCOL1) or by the change of the transcript level (LpFT3). Gene expression changes over a vernalisaton time course were also analysed and results indicated that LpFT3 acts as the flowering integrator. The role of LpGI, LpCOL1, and LpFT3 as putative photoperiod genes was further confirmed by genetic mapping, which placed them on linkage groups 3, 6, and 7, respectively. The syntenic positions in rice contain major heading date quantitative trait loci. The function of LpFT3 was examined by over-expressing the gene in Arabidopsis under control of the cauliflower mosiac virus (CaMV) 35S promoter. Substantially higher expression of the endogenous Arabidopsis AtFT transcript was observed in the mutated ft-1 line overexpressing LpFT3, suggesting a positive feedback loop either directly or through upstream intermediaries. Overexpression of the LpGI and LpFT3 genes restored rapid flowering to the respective gi-3 and ft-1 Arabidopsis mutants while overexpression of LpCOL1 did not accelerate flowering either in co-2 or wild type Arabidopsis plants. However, overexpression of LpCOL1 completely restored the late flowering phenotype of the gi-3 mutant indicating the existence of another important link outside the well established hierarchy of GI-CO-FT in the photoperiod pathway. This study revealed that the ryegrass photoperiod pathway genes show high similarity to their wheat, rice and Arabidopsis counterparts. Exploring ways to modulate flowering time in ryegrass could provide major benefits to the agricultural industry by increasing forage quality, controlling seed and pollen production, and addressing potential problems linked with climate change.

Grasslands account for almost one quarter of the world’s cover of vegetation. Almost three quarter of the world’s milk, beef and veal are produced from temperate grasslands. In New Zealand, ryegrass (Lolium perenne) is the main pasture constituent with more than half of the total export revenue coming from grass-related products. Much of ryegrass production and quality depends on the timing of flowering through seasonal progression. In many plants, day length is the critical environmental parameter that controls when plants begin to flower. In Arabidopsis the CONSTANS (CO) gene mediates day length response. Upstream of CO is the GIGANTEA (GI) gene which is associated with the circadian clock mechanism and is required to promote CO expression. The FT gene is the immediate downstream genetic target of CO and is a direct promoter of flowering. In this study, cDNA libraries, sequence alignment and genome walking were used to sequence and describe three putative orthologues from the ryegrass photoperiod pathway: LpGI, LpCOL1, and LpFT3. All three behaved in a true photoperiod manner characterised by cycling expression patterns under continuous light conditions and differential expression patterns in LD and SD conditions. Different photoperiods brought about differences in expression of these genes measured either by the phase shift change (LpGI and LpCOL1) or by the change of the transcript level (LpFT3). Gene expression changes over a vernalisaton time course were also analysed and results indicated that LpFT3 acts as the flowering integrator. The role of LpGI, LpCOL1, and LpFT3 as putative photoperiod genes was further confirmed by genetic mapping, which placed them on linkage groups 3, 6, and 7, respectively. The syntenic positions in rice contain major heading date quantitative trait loci. The function of LpFT3 was examined by over-expressing the gene in Arabidopsis under control of the cauliflower mosiac virus (CaMV) 35S promoter. Substantially higher expression of the endogenous Arabidopsis AtFT transcript was observed in the mutated ft-1 line overexpressing LpFT3, suggesting a positive feedback loop either directly or through upstream intermediaries. Overexpression of the LpGI and LpFT3 genes restored rapid flowering to the respective gi-3 and ft-1 Arabidopsis mutants while overexpression of LpCOL1 did not accelerate flowering either in co-2 or wild type Arabidopsis plants. However, overexpression of LpCOL1 completely restored the late flowering phenotype of the gi-3 mutant indicating the existence of another important link outside the well established hierarchy of GI-CO-FT in the photoperiod pathway. This study revealed that the ryegrass photoperiod pathway genes show high similarity to their wheat, rice and Arabidopsis counterparts. Exploring ways to modulate flowering time in ryegrass could provide major benefits to the agricultural industry by increasing forage quality, controlling seed and pollen production, and addressing potential problems linked with climate change.

Grasslands account for almost one quarter of the world’s cover of vegetation. Almost three quarter of the world’s milk, beef and veal are produced from temperate grasslands. In New Zealand, ryegrass (Lolium perenne) is the main pasture constituent with more than half of the total export revenue coming from grass-related products. Much of ryegrass production and quality depends on the timing of flowering through seasonal progression. In many plants, day length is the critical environmental parameter that controls when plants begin to flower. In Arabidopsis the CONSTANS (CO) gene mediates day length response. Upstream of CO is the GIGANTEA (GI) gene which is associated with the circadian clock mechanism and is required to promote CO expression. The FT gene is the immediate downstream genetic target of CO and is a direct promoter of flowering. In this study, cDNA libraries, sequence alignment and genome walking were used to sequence and describe three putative orthologues from the ryegrass photoperiod pathway: LpGI, LpCOL1, and LpFT3. All three behaved in a true photoperiod manner characterised by cycling expression patterns under continuous light conditions and differential expression patterns in LD and SD conditions. Different photoperiods brought about differences in expression of these genes measured either by the phase shift change (LpGI and LpCOL1) or by the change of the transcript level (LpFT3). Gene expression changes over a vernalisaton time course were also analysed and results indicated that LpFT3 acts as the flowering integrator. The role of LpGI, LpCOL1, and LpFT3 as putative photoperiod genes was further confirmed by genetic mapping, which placed them on linkage groups 3, 6, and 7, respectively. The syntenic positions in rice contain major heading date quantitative trait loci. The function of LpFT3 was examined by over-expressing the gene in Arabidopsis under control of the cauliflower mosiac virus (CaMV) 35S promoter. Substantially higher expression of the endogenous Arabidopsis AtFT transcript was observed in the mutated ft-1 line overexpressing LpFT3, suggesting a positive feedback loop either directly or through upstream intermediaries. Overexpression of the LpGI and LpFT3 genes restored rapid flowering to the respective gi-3 and ft-1 Arabidopsis mutants while overexpression of LpCOL1 did not accelerate flowering either in co-2 or wild type Arabidopsis plants. However, overexpression of LpCOL1 completely restored the late flowering phenotype of the gi-3 mutant indicating the existence of another important link outside the well established hierarchy of GI-CO-FT in the photoperiod pathway. This study revealed that the ryegrass photoperiod pathway genes show high similarity to their wheat, rice and Arabidopsis counterparts. Exploring ways to modulate flowering time in ryegrass could provide major benefits to the agricultural industry by increasing forage quality, controlling seed and pollen production, and addressing potential problems linked with climate change.

Grasslands account for almost one quarter of the world’s cover of vegetation. Almost three quarter of the world’s milk, beef and veal are produced from temperate grasslands. In New Zealand, ryegrass (Lolium perenne) is the main pasture constituent with more than half of the total export revenue coming from grass-related products. Much of ryegrass production and quality depends on the timing of flowering through seasonal progression. In many plants, day length is the critical environmental parameter that controls when plants begin to flower. In Arabidopsis the CONSTANS (CO) gene mediates day length response. Upstream of CO is the GIGANTEA (GI) gene which is associated with the circadian clock mechanism and is required to promote CO expression. The FT gene is the immediate downstream genetic target of CO and is a direct promoter of flowering. In this study, cDNA libraries, sequence alignment and genome walking were used to sequence and describe three putative orthologues from the ryegrass photoperiod pathway: LpGI, LpCOL1, and LpFT3. All three behaved in a true photoperiod manner characterised by cycling expression patterns under continuous light conditions and differential expression patterns in LD and SD conditions. Different photoperiods brought about differences in expression of these genes measured either by the phase shift change (LpGI and LpCOL1) or by the change of the transcript level (LpFT3). Gene expression changes over a vernalisaton time course were also analysed and results indicated that LpFT3 acts as the flowering integrator. The role of LpGI, LpCOL1, and LpFT3 as putative photoperiod genes was further confirmed by genetic mapping, which placed them on linkage groups 3, 6, and 7, respectively. The syntenic positions in rice contain major heading date quantitative trait loci. The function of LpFT3 was examined by over-expressing the gene in Arabidopsis under control of the cauliflower mosiac virus (CaMV) 35S promoter. Substantially higher expression of the endogenous Arabidopsis AtFT transcript was observed in the mutated ft-1 line overexpressing LpFT3, suggesting a positive feedback loop either directly or through upstream intermediaries. Overexpression of the LpGI and LpFT3 genes restored rapid flowering to the respective gi-3 and ft-1 Arabidopsis mutants while overexpression of LpCOL1 did not accelerate flowering either in co-2 or wild type Arabidopsis plants. However, overexpression of LpCOL1 completely restored the late flowering phenotype of the gi-3 mutant indicating the existence of another important link outside the well established hierarchy of GI-CO-FT in the photoperiod pathway. This study revealed that the ryegrass photoperiod pathway genes show high similarity to their wheat, rice and Arabidopsis counterparts. Exploring ways to modulate flowering time in ryegrass could provide major benefits to the agricultural industry by increasing forage quality, controlling seed and pollen production, and addressing potential problems linked with climate change.

Red firespike (Odontonema strictum) is an ornamental shrub with potential for use as a flowering potted plant due to its dark green foliage and attractive red flower spikes. Studies were conducted to evaluate the effect of photoperiod and plant growth retardants on firespike growth and flower initiation and development. Firespike is reported to be a short day plant. To determine the critical photoperiod requirements to initiate flowering, plants were placed in short days (SD) for 0, 8, 16, 24, or 32 days before being returned to long days (LD). Meristems were sampled 0 or 8 days after return to LD for histological examination. Plants receiving only 8 SD showed early floral initiation; however, plants receiving 16 or more SD reached anthesis earlier than plants grown under fewer SD. To evaluate the effects of light intensity and temperature on flowering and growth characteristics of firespike, two experiments were conducted. Plants were grown under LD or SD, 0%, 45% or 65% shade and temperatures of 15, 25 or 35°C. Plants grown under 45% shade and LD and 65% shade and SD had greatest and least height, respectively. The first open flower was observed after 92 days under no shade while 45% shade in both LD and SD resulted in more inflorescences. To evaluate effectiveness of various plant growth regulators on firespike height control, foliar and drench applications of uniconazole, flurprimidol, daminozide, and paclobutrazol were examined in two experiments. The results showed flurprimidol and paclobutrazol drenches at 0.24 and 0.35 mg a.i./pot could be used to control the growth of red firespike more effectively than other PGRs. However, growth index decreased up to 88% and 84% when paclobutrazol and flurprimidol were applied at 0.59 and 0.71 mg a.i./pot, respectively. The morphological and physiological characteristics of firespike treated with paclobutrazol and flurprimidol under drought stress were studied. Drought stress delayed days to flowering and number of replications flowering. Application of paclobutrazol and flurprimidol enhanced drought resistance of red firespike reducing adverse effects of water stress during the experiment.

Colostrum quality is critical to calf health as colostrum provides immunoglobulins (Ig) that are critical for a calf's immune system. Despite close management of factors known to affect colostrum production, 23% of dairy cows are still producing inadequate volume or quality of colostrum, which causes calf death and poor performance. Therefore, the objectives of this dissertation are to investigate factors that affect colostrum production and methods to improve colostrum yield and quality. Based on previous literature showing that photoperiod impacts milk yield post-calving in dry cows and that light intensity and temperature-humidity index (THI) impact colostral Ig content, I hypothesized that photoperiod and THI during the dry period impact colostrum yield and quantity in Holstein and Jersey cows. The first study evaluated the isolated effect of photoperiod on colostrum production. Dry cows were housed in a temperature-controlled barn and exposed to either short-day photoperiod (SDPP) of 8 h of light per day or long-day photoperiod (LDPP) of 16 h of light per day for the entire dry period until calving. Altered photoperiod had no effect on colostrum yield, Ig content or other components of colostrum. However, Jersey cows had a higher Brix score, fat, protein, IgA and IgM. After calving, milk production was not affected by photoperiod treatment, likely due to cows being exposed to an irregular lighting scheme. The second study evaluated the combined effects of photoperiod and THI during the dry period on colostrum production and broke cows into a bottom (1), middle (2) and top (3) third based on their photoperiod exposure. Holstein cows produced more colostrum than Jersey cows in each photoperiod category. For both breeds, photoperiod category 1 cows produced less colostrum than cows in photoperiod category 2 and 3. Brix score did not differ by breed but differed by farm and photoperiod category with farm 1, photoperiod category 3 cows having increased Brix score compared to farm 2, photoperiod category 1 and 2 cows. Colostrum components for Jersey cows did not differ by photoperiod category. However, colostrum volume, Brix score, protein and SNF were all impacted by THI and (or) photoperiod variables in predictive modeling. This indicates that colostrum yield and quality in Holstein and Jersey cows are similarly impacted by both photoperiod exposure and THI exposure during the last two months of pregnancy. Therefore, farmers can utilize short-day photoperiod during the dry period during times of moderate THI to improve milk production post-calving without negatively impacting colostrum production. However, future studies are needed to tease out THI and photoperiod impact on colostrum on a large scale in order to improve dry cow management and colostrum production. / Doctor of Philosophy / Cows do not transfer antibodies or immunoglobulins to their offspring during gestation and calves are born deficient in antibodies that are critical for a healthy immune system. Instead, cows transfer antibodies into the first milk that they produce, termed colostrum. After calves ingest the colostrum, the antibodies are absorbed by the small intestine and enter circulation where they can traverse the body to identify and neutralize pathogens. To ensure adequate immune system function, calves must ingest 150 – 200 g of antibodies within 6 h of birth. However, around 23% of cows do not produce enough antibodies in their colostrum or have low colostrum yield overall. 19% of calves do not ingest enough antibodies and will die or have negative health effects that persist into adulthood as a result. Therefore, the objective of this dissertation is to investigate methods to improve colostrum production in cows to improve calf health and reduce calf deaths. While several factors that affect colostrum production have been identified and are managed for optimum colostrum production, there is still high variation in colostrum production from cow to cow. Based on previous research showing that colostrum yield varies seasonally and that daily light exposure, or photoperiod, can impact milk production, I hypothesized that photoperiod and temperature-humidity index (THI) during the last two months of pregnancy impact colostrum production in cows. The first study was designed to isolate the effect of photoperiod on colostrum, by housing Holstein and Jersey cows in a temperature-controlled barn during the last two months of pregnancy and exposing them to varying daylengths. Cows were exposed to either a short-day photoperiod of 8 h of light per day or a long-day photoperiod of 16 h of light per day. When the cows gave birth, they were milked and the amount of colostrum produced and the components of the colostrum were evaluated. A Brix refractometer, which is widely used by farmers to estimate colostrum quality as it is an on-farm tool that estimates colostrum antibody content, was also used in this study. Cows were returned to ambient photoperiod and milk, fat and protein production were tracked for 15 weeks. I found that altered photoperiod had no effect on colostrum yield, antibody content or other components of colostrum. However, Jersey cows had a higher Brix score, fat, protein, antibody IgA and antibody IgM. After calving, milk production was not affected by photoperiod treatment, likely because of irregular lighting exposure after calving. These data indicate that photoperiod alone may not be causing the seasonal variations associated with colostrum production. Therefore, a second study was conducted to evaluate the effects of photoperiod and THI together on subsequent colostrum production in Holstein and Jersey cattle by month. Colostrum production and weather data were collected for cows housed in ambient photoperiod and THI for the last two months of pregnancy from two different farms. Cows were divided into a bottom (1), middle (2) and top (3) third based on their photoperiod exposure. Holstein cows produced more colostrum than Jersey cows in each photoperiod category. For both breeds, photoperiod category 1 cows produced less colostrum than cows in photoperiod category 2 and 3. Brix score did not differ by breed but differed by farm and photoperiod category with farm 1, photoperiod category 3 cows having increased Brix score compared to farm 2, photoperiod category 1 and 2 cows. Colostrum components for Jersey cows did not differ by photoperiod category. However, colostrum volume, Brix score, protein and SNF were all impacted by THI and (or) photoperiod variables in predictive modeling. This indicates that colostrum yield and quality in Holstein and Jersey cows are similarly impacted by both photoperiod exposure and THI exposure during the last two months of pregnancy. Data from these studies are the first to show the isolated effect of photoperiod on colostrum production in Jersey cows and the second showing data on Holstein cows. Recommendations have already been made to dairy producers to limit photoperiod exposure during the last two months of pregnancy in order to increase milk production post-calving. This study shows that limiting photoperiod will not compromise colostrum production in cows. However, I also found that colostrum production is also impacted by THI exposure and that colostrum yield and quality have inverse relationships with photoperiod and THI exposure. Whereas colostrum yield increases with increased photoperiod and THI, Brix score decreases. Therefore, managing for increased colostrum quality is compromised by colostrum yield. This study also found that the widely accepted indirect measure of antibody content, the Brix score, was not a reliable estimate of antibody content and instead, a better indicator of solids content of colostrum. In conclusion, these data show that photoperiod alone does not impact colostrum production, rather a combined effect of photoperiod and THI are responsible for seasonal variation in colostrum and differences between breeds of cow are also evident. In addition, Brix score may not be the best indicator of colostrum quality and could be replaced by more reliable methods by dairy farmers to ensure that adequate colostrum is fed to calves. Future studies will need to explore differences in response to photoperiod vs. THI alteration and explore genetic associations with colostrum production, to identify which genes are associated with increased colostrum quality in Jersey cows so that we may genetically select for increased colostrum quality.