Pollination patterns in safflower (Carthamus tinctorius L.) : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science in Plant Science at Massey University

Abstract

The influence of environmental conditions on safflower (Carthamus tinctorius L.) floret characters and insects were studied in relation to pollination in this species. Insect activity was studied in a field experiment using part of the world germplasm collection of safflower. Honey bees were the most likely cross-pollinators. Activity of honey bees did not vary between genotypes studied. Correlations between insect and weather data were mainly non-significant. A sample of 12 genotypes from the world collection were intensively studied in controlled environment rooms. Single plants were used as plots in a randomised complete block design, in each of four environments (day/night temperature treatments of 28/22°c and 24/l8°c in combination with vapour pressure deficit treatments of -1.0 and -0.4 kPa). Environments reflected New Zealand summer conditions. Coefficients of variation were acceptable for most characters. Considerable genotypic, environmental and genotype-environment interaction variances were observed for most characters. Standardised partial regression coefficients (path coefficients) and principal factors were utilized to determine the characters most important in self-pollination of safflower. These characters were: the length of the style-stigma; the rate of style-stigma growth; the rate of corolla tube growth and amounts of viable pollen present during floret expansion. Pollen viabilities remained high for the longest time in higher humidity environments. Large amounts of pollen were produced at the lower humidity. Floral parts were largest in the cool dry environment, however rates of style-stigma and corolla expansion were greater at lower temperatures. It was concluded that synchronization of the rates of style-stigma and corolla tube growth were important in maintaining the stigma in close proximity to viable pollen, and thus promoting the possibility of self-pollination. Self-pollination was greatest at the lower temperature and lower humidity. The basic self-pollination mechanism observed was in agreement with previous authors. A number of improvements for future controlled environment experiments involving safflower were suggested. The implications of pollination of safflower on germplasm collection and maintenance, artificial crossing and breeding plans were discussed