The development of the unisexual male and female flowers of Zea mays from bisexual initials in both tassels and ears has been reinvestigated with SEM and TEM. The early stages of spikelet branch primordia, spikelet initiation, and early flower development are similar in both flowers, though differences in rates of growth of glumes, lemmas, and palea were detected. In both tassel and ear flowers, a pair of stamens arises opposite the lemmas and a third stamen initiates later at right angles to the first pair but from a point on the meristem below its insertion. Gynoecia develop on both tassel and ear flowers first as a ridge which overgrows the apical meristem giving rise to the stylar canal and the elongate silk. Male flowers arise in the tassel through selective vacuolation and abortion of the cells of the early gynoecium. The single female flower in each ear spikelet arises through the vacuolation and abortion of stamens in the upper flower and the repression of growth of and the eventual regression of the lower flower in each spikelet. The significance of these selective organ abortions for practical applications is discussed.

The experience of multiple chronic illnesses has a distinct pattern of development and consequence, involving challenges to personal identity and the benefits of social support from and to others. Our results suggest that programmes addressing the needs of persons with multiple chronic conditions might tailor interventions in ways that maximally address their unique challenges.

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Subjecting 5-day-old plumules of corn (Zea mays L.) to elevated temperatures for brief periods of time causes the pattern of protein synthesis to shift from the production of a broad spectrum of proteins to the new and (or) enhanced synthesis of a small number of heat-shock polypeptides (HSPs). Most notable is the depressed synthesis of a major polypeptide (relative mass (Mr) = 93 000 and isoelectric point = 8.0) normally made at 27 degrees C and the enhanced and (or) new synthesis of polypeptides with MrS of 108 000, 89 000, 84 000, 76 000, 73 000, and 18 000, following 1 h of heat shock. These six HSPs is observed within 120 min following heat shock. Recovery from heat shock is rapid; after 6 to 8 h at 27 degrees C following heat shock, the polypeptide pattern is indistinguishable from the control. Extracts from individual heat-shocked shoots produced polypeptide synthetic patterns identical to those from extracts from 20 shoots, regardless of whether single shoots were intact or excised during labelling. Single 5-day-old primary roots exhibited polypeptide synthetic patterns and responded to heat shock in a manner similar to shoots. This is the first demonstration of the induction of heat-shock polypeptides in a whole, intact higher plant.

The small (18-kDa) heat shock proteins (hsps) of maize are encoded by a complex multigene family. In a previous report, we described the genetic information from cDNAs encoding two different members of the family. In this communication, we report the isolation and characterization of cDNA and genomic clones encoding information for a third member of this hsp family (c/gMHSP18-1). DNA fragments containing nucleotide sequences common to, or specific for, each of these characterized 18-kDa genes were prepared and used as probes to assess the expression of these genes during microsporogenesis and development of the gametophyte in an inbred line of maize (Oh43). Our results demonstrate (1) that mRNA transcripts encoding the 18-kDa hsps are expressed and/or accumulate during microsporogenesis, and (2) that genes encoding two of the characterized 18-kDa hsps are expressed and/or accumulate independently, in a stage-specific manner during microsporogenesis. These observations imply that the stage-specific expression of particular 18-kDa hsp genes results from gene-specific regulation during microsporogenesis and gametophyte development rather than from an overall activation of the heat shock or stress response.