Wild Brassica plants release seeds by a pod shattering mechanism; in related crop plants, such as oil‐seed rape, this can result in substantial loss of seed, and hence loss of revenue, and also in the distribution of seeds which can contaminate future crops and the environment. To identify strategies which may be used to reduce shatter, either by conventional breeding programmes or by genetic engineering, we have examined fruit development in oil‐seed rape (Brassica napus), and in the related B. juncea and Arabidopsis, using a combination of cytological, cytochemical and molecular techniques. We report here on the patterns of cellular differentiation and tissue development during fruit maturation, and suggest how this results in the shattering phenotype.

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Enzymatically isolated vein networks from mature pea (Pisum sativum L. cv Alaska) leaves were employed to investigate the properties of sucrose loading and the effect of phytohormones and cell turgor on this process. The sucrose uptake showed two components: a saturable and a first-order kinetics system. The high affinity system (K(m), 3.3 millimolar) was located at the plasmalemma (p-chloromercuriphenylsulfonic acid and orthovanadate sensitivity). Further characterization of this system, including pH dependence and effects of energy metabolism inhibitors, supported the H(+)-sugar symport concept for sucrose loading. Within a physiological range (0.1-100 micromolar) and after 90 min, abscisic acid (ABA) inhibited and gibberellic acid (GA(3)) promoted 1 millimolar sucrose uptake. These responses were partially (ABA) or totally (GA(3)) turgor-dependent. In experiments of combined hormonal treatments, ABA counteracted the GA(3) positive effects on sucrose uptake. The abolishment of these responses by p-chloromercuriphenylsulfonic acid and experiments on proton flux suggest that both factors (cell turgor and hormones) are modulating the H(+) ATPase plasmalemma activity. The results are discussed in terms of their physiological relevance.

Structural changes of tissues in unpollinated ovaries of Pisum sativum L. cv. Alaska after treatment with different plant growth substances (gibberellic acid, 2,4‐dichlorophenoxyacetic acid, and 6‐benzyladenine) or decapitation of the plant were studied. All the treatments resulted in the prevention of cellular disorganization associated with ovary senescence. They effected the enlargement of mesocarp cells and the differentiation of endocarp cells in very similar patterns, suggesting a similar induction of the structural processes involved in fruit development. Ultrastructural changes in mesocarp cells after treatment with gibberellic acid showed that rapid enlargement of mesocarp cells was sustained mainly by a reorganization of the membrane systems directed to the sysnthesis of primary cell wall. Early changes in the subcellular components in mesocarp cells were observed as the first symptoms in ovary senescence.

J. 1989. Biochemical and histochemical detection of endoproteolytic activities involved in ovary senescence or fruit development in Pisum sativum. -Physiol, Plant. 76: 405-411.The appearance of endoproteolytic activities related to the senescence of unpollinated pea {Pisum sativum L. cv. Alaska) ovaries, or with fruit development induced by gibberellic acid (GA,), was examined simultaneously by biochemical and histochemical techniques using gelatin as substrate. Biochemical detection was carried out by gelatin-containing sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. Histochemical detection was performed using a gelatin film technique. No differences in endopeptidase activity were found in extracts from non-treated or developing ovaries during the two first days post-anthesis. After day 3 non-treated ovaries showed a marked increase in activity as well as two new bands with proteolytic activity, associated with the beginning of the senescence. At the same time a new activity was also located at the endocarp. In developing ovaries activity was only observed around vascular cells of the mesocarp at the end of the period studied (4-5 days post-anthesis). Activity detected in the ovules was essentially the same in both GAj-treated and non-treated ovaries.