The aim of the study was to determine the effect of photoperiod on production of quail in South Africa. Day old chicks were randomly divided into two groups. One group (n=74) received continuous light (LL) while the other group (n=77) received 13 h of light (LD) per day. Traits measured were sexual characteristics (age at sexual maturity and testis weight, egg production and egg weight) and growth (body weight) development in males and females respectively. Significant differences in growth existed between sexes; females were 171.44±17.15 and 182.91±17.75 g compared to the 151.77±13.20 and 155.00±16.86 g for males in both LL and LD groups respectively. Both males and females in the LL group initially outperformed the LD group in growth rate but, by day 72 the LD group had compensated and were 4.6% heavier than the LL group. A similar trend was observed for sexual maturity between the LL and LD groups. However, photoperiod did significantly influence initial egg production in favour of the LL group. The LL group had 80% of the females in production by day 44 compared to the 60% of the LD group. The initial egg weight of the LL group was 14 % higher than those of the LD group. Quail subjected to continuous light attained earlier sexual maturity and production with lower final weight compared to quail subjected to an intermediate photoperiod. The application of a longer photoperiod would therefore favour an egg production system.

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

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Call number: LD2668 .T4 1979 B69 / Master of Science

In effort to breed for daylength-neutral (DNP) soybean germplasms (Glycine max (L.) Merrill), selected longday cultivars (LDP) from Maturity Group 00 were crossed to local adapted shortday cultivars (DP) from Maturity Group VI. In the segregating populations there were many new hybrid combinations, some of which flowered and set pod as early as the Group 00 parents, however, they were larger in size and matured normally. These lines were considered daylength-neutral plants (DNP), and were evaluated in the field nursery in biweekly date of planting experiments from early May to late July during 1978 and 1979. Selected LDP and local adapted SDP cultivars were utilized as check lines. It was observed that LDP cultivars flowered and set pods normally. However, they did not mature normally; the pods ripened and shattered while the stem and leaves remained green and these plants were short and unproductive. Local SDP were the most sensitive plants in response to the change in planting date and daylength. Number of days to flowering, pod setting, and maturity as well as plant heights had decreased sharply in response to the decrease in daylength of later planting dates. In contrast, DNP lines flowered, set pod and matured normally on large vigorous plants in approximately the same period of time regardless of planting date or the daylength during the growing season. To study the inheritance of the daylength-neutral trait in soybeans, crosses were made between DNP lines and local SDP cultivars. These were extremely wide crosses. Segregating populations from these crosses were tested under three light treatments of 12, 18 and 24 hours. Only DNP plants flowered and set pod normally under the long photoperiod treatments of 18 and 24 hours. The magnitude and continuous nature of the frequency distribution of the segregating populations as well as the low heritability estimates of each trait imply that this response is under polygenic control.

Call number: LD2668 .T4 1986 G36 / Master of Science / Agronomy