Reproductive ecology and postpollination development in the hydrophilous monocot Ruppia maritima.

PREMISE: Water-pollination (hydrophily) is a rare but important pollination mechanism that has allowed angiosperms to colonize marine and aquatic habitats. Hydrophilous plants face unique reproductive challenges, and many have evolved characteristic pollen traits and pollination strategies that may have downstream consequences for pollen performance. However, little is known about reproductive development in the life history stage between pollination and fertilization (the progamic phase) in hydrophilous plants. The purpose of this study was to characterize reproductive ecology and postpollination development in water-pollinated Ruppia maritima L. METHODS: Naturally pollinated inflorescences of R. maritima were collected from the field. Experimental pollinations using both putatively outcross and self pollen were conducted in the greenhouse and inflorescences were collected at appropriate intervals after pollination. Pollen reception, pollen germination, pollen tube growth, and carpel morphology were characterized. RESULTS: Ruppia maritima exhibits incomplete protogyny, allowing for delayed selfing. Pollen germinated within 15 min after pollination. The average shortest possible pollen tube pathway was 425 µm and pollen tubes first reached the ovule at 45 min after pollination. The mean adjusted pollen tube growth rate was 551 µm/h. CONCLUSIONS: Ruppia pollen is adapted for rapid pollen germination, which is likely advantageous in an aquatic habitat. Small effective pollen loads suggest that pollen competition intensity is low. Selection for traits such as a long period of stigma receptivity, fast pollen germination, and carpel morphology likely played a larger role in shaping postpollination reproductive development in Ruppia than evolution in pollen tube growth rates.

Effect of high-oleic and high-linoleic safflower oils on mammary tumors induced in rats by 7,12-dimethylbenz(alpha)anthracene.

A mutant safflower oil, rich in oleic acid, was used for a critical test of the hypothesis that polyunsaturated fats act as co-carcinogens. Weanling female rats were each given 5 mg of 7,12-dimethylbenz(alpha)anthracene. They were then pair-fed diets containing 20%, by weight, of conventional high-linoleic safflower oil; a mutant high-oleic safflower oil; or coconut oil. Half of each group received supplementary DL-alpha-tocopherol. Tumors were identified by two observers, by palpation. Data on incidence of tumors and on numbers of tumors per affected rat led to similar conclusions. At 16 weeks, there were significant differences when supplementary tocopherol was included in the diet: the group fed high-oleic safflower oil had more tumors than the group fed coconut oil. This difference was not seen in the absence of supplementary tocopherol. When the data for tocopherol-supplemented and unsupplemented subgroups were combined, the high-oleic safflower oil group had significantly more tumors than did the coconut oil group. The high-linoleic safflower oil group was not significantly different from either of the other groups. In all groups, histologic examination of the largest tumor in each rat revealed more benign tumors, mostly duct papillomas, than carcinomas.

Composition of lipids in human serum and adipose tissue during prolonged feeding of a diet high in unsaturated fat.

Elderly institutionalized men were assigned at random to two groups, one of which received a conventional diet while the other was fed a diet in which the major modification was substitution of unsaturated for saturated fat. Changes in serum lipids and in adipose tissue over periods up to 5 years are described. In control subjects, mean serum cholesterol rose 4% over the first 20 months, then fell during the next 40 months to a level 10% below the starting concentration. In the experimental group there was an immediate drop, followed by further changes roughly parallel to those in the control subjects. The mean difference between the control and experimental groups was 14.0% of the starting level. Changes in serum total lipid were similar, but the percentage difference between control and experimental groups was only 6.8% of the baseline level. All major esterified serum lipid fractions of experimental subjects contained increased concentrations of linoleic acid. This was most marked in triglyceride, which at 3 years had a composition similar to that of the dietary fat in both groups of subjects. Adipose tissue linoleic acid rose in men on the experimental diet from 11% of total fatty acid at time zero to 32% at 5 years. The rise could be fitted to an exponential function with a half-time of 680 days. The rate of rise during the 1st year was correlated negatively with initial body weight and positively with weight gain; the influence of adherence to the diet was much less pronounced.