The blind mutant of Petunia hybrida Hort. is characterized by a flower with a highly modified corolla: the much reduced or lacking corolla tube lamina is replaced by five supernumerary anthers, which produce scarce but fertile pollen. The ontogenic study of stamen and corolla formation shows the existence of three separate morphogenetic patterns corresponding to the development of undifferentiated appendages, the formation of pollen sacs or floral appendages, and the final intercalary growth (filament and corolla tube elongation), respectively. A first interpretative scheme of the floral morphogenesis is proposed and discussed.
Summary
Effects of the herbicide EL‐107 (N‐[3‐(1‐ethyl‐1‐methylpropyl)‐5‐isoxazolyl]‐2,6‐dimethoxy‐benzamide) on the growth of dicotyledonous plants are described. The herbicide did not inhibit germination but reduced the growth of rape (Brassica napus L.) by half at 0.0057 mg l−1. The most characteristic symptom induced was a swelling of the apical regions, and histological observations of root tips of Polygonum persicaria and rape revealed a progressve disappearance of the meristematic zone, which was replaced by enlarged cells almost devoid of cytoplasm. Growth of cells of Acer pseudoplatanus L. and soybean (Glycine max L.) cultured in suspension was also inhibited by EL‐107, which induced a characteristic change in the cell morphology to an enlarged, rounded shape. EL‐107 apparently did not block cell division; at a high concentration it produced some inhibition of protein synthesis, but in Acer cells only. In both types of cell cultures it inhibited, to some extent, the incorporation of glucose into cell wall material.
The ovaries of two different Petunia species: Petunia hybrida (hort) and Petunia parodii (Steere) were irradiated with τ-ray doses ranging from 50 to 1,000 Gy before pollination. Seed setting occurred after 4 days preculture on a non-sterile medium. Ovaries transformed into fruits were then cultivated aseptically with the following results: (1) τ-ray doses ranging from 200 to 1,000 Gy led to the development of two types of plants: haploids 2n=x=7 and overdiploids 2n>2x=14. (2) The androgenetic origin of haploids was ascertained by using genetic markers. The origin of overdiploids is discussed. (3) Androgenetic haploids contained the chloroplasts of the irradiated female parent. No visible change of cp DNA patterns was observed after irradiation. (4) The four possible androgenetic events were successfully obtained between the two Petunia species: hybrida haploids with hybrida or parodii cytoplasm, and parodii haploids with parodii or hybrida cytoplasm.
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