Characterisation of inflorescence development in Zea mays with four developmental mutants : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Biological Science at Massey University, Palmerston North, New Zealand

The genetic control of inflorescence development has been studied in great detail in the model dicotyledonous plants Arabidopsis thaliana and Antirrhinum majus. In contrast, little is known about the genetic regulation in monocotyledonous species. Using maize (Zea mays) as a model system, the phenotypes were documented for the branched silkless1 (bd1) and ramosa (ra1, ra2, and ra3) inflorescence mutants that are characterised by abnormally branched ears. A comparison of the adult morphology and developing inflorescences using scanning electron microscopy in mutant and normal maize reveals that there are at least five reproductive meristems that can be identified in maize: the inflorescence meristem, the branch meristem, the spikelet pair meristem, the spikelet meristem, and the floret meristem. The abnormal branching in bd1 and the three-ramosa mutations is the result of the failure to determine the fate of specific types of reproductive meristems in both tassels and ears. Both RA1 and RA3 are required for the determination of spikelet pair development in branch primordia. RA2 is necessary for determinate growth in spikelet pair meristems. BD1 is required determinate growth of spikelet meristems by specifying a determinate floral meristem identity. The classification of the different types of reproductive meristems and the genes that regulate their development is essential to understanding the genetic programs that underlie inflorescence morphogenesis in maize and other Gramineae

Investigation of the Problems of Lunar and Planetary Exploration Annual Report, 1 Dec. 1964 - 30 Nov. 1965

Problems of lunar and planetary exploratio

The properties of dynamically ejected runaway and hyper-runaway stars

Runaway stars are stars observed to have large peculiar velocities. Two mechanisms are thought to contribute to the ejection of runaway stars, both involve binarity (or higher multiplicity). In the binary supernova scenario a runaway star receives its velocity when its binary massive companion explodes as a supernova (SN). In the alternative dynamical ejection scenario, runaway stars are formed through gravitational interactions between stars and binaries in dense, compact clusters or cluster cores. Here we study the ejection scenario. We make use of extensive N-body simulations of massive clusters, as well as analytic arguments, in order to to characterize the expected ejection velocity distribution of runaways stars. We find the ejection velocity distribution of the fastest runaways (>~80 km s^-1) depends on the binary distribution in the cluster, consistent with our analytic toy model, whereas the distribution of lower velocity runaways appears independent of the binaries properties. For a realistic log constant distribution of binary separations, we find the velocity distribution to follow a simple power law; Gamma(v) goes like v^(-8/3) for the high velocity runaways and v^(-3/2) for the low velocity ones. We calculate the total expected ejection rates of runaway stars from our simulated massive clusters and explore their mass function and their binarity. The mass function of runaway stars is biased towards high masses, and depends strongly on their velocity. The binarity of runaways is a decreasing function of their ejection velocity, with no binaries expected to be ejected with v>150 km s^-1. We also find that hyper-runaways with velocities of hundreds of km s^-1 can be dynamically ejected from stellar clusters, but only at very low rates, which cannot account for a significant fraction of the observed population of hyper-velocity stars in the Galactic halo.Comment: Now matching published ApJ versio