Time until floral closure
Permanent floral closure occurred between 4·2 and 6·5 h after pollination in female flowers and between 5·0 and 7·0 h after pollination in perfect flowers. The average time from pollination to floral closure in female flowers [5·38 ± 0·13 h (mean ± standard error), n = 30] was significantly shorter than that in perfect flowers with cross-pollination (6·20 ± 0·10 h, n = 22; t = –4·537, d.f. = 50, P < 0·001). When floral closure occurred, 76·67 % of female flowers and 100 % of perfect flowers were fertilized. The average number of fertilized ovules was 2·700 ± 0·445 (n = 30) in female flowers and 8·364 ± 0·973 (n = 22) in perfect flowers. The difference between morphs was significant (t = –5·780, d.f. = 50, P < 0·001), due to the difference at the time of floral closure. In this study, pollen grains germinated within 2 h following pollination. The length of time after pollination and the number of fertilized ovules showed a significant quadratic relationship (r2 = 0·805, F = 237, P < 0·0001; Fig. ). At the time when floral closure occurred, the number of fertilized ovules was low, and more than half of the ovules were fertilized between 16 and 24 h after pollination (Fig. ).
Fig. 2. The relationship between sampling time after pollination and the number of fertilized ovules in C. delavayi. Fractions indicate the proportion of fertilized flowers, calculated by number of flowers with fertilized ovules divided by the total number of (more ...)
The effects of pollen-load size on floral closure and female fitness
For female recipients, 20 grains were adequate to induce closure in over half (63·5 %) of the flowers. PC increased significantly with increasing pollen load (Fig. A; χ2 = 23·451, d.f. = 2, P < 0·0001). Pollen-load size had significant positive effects on female fitness (one-way ANOVA, F2,160 = 162·418, P < 0·001 for PD; F2,160 = 14·213, P < 0·001 for NF; F2,160 = 11·486, P < 0·001 for PF; F2,160 = 7·272, P = 0·001 for SN and F2,160 = 5·907, P = 0·003 for SS). NF, PF, SN and SS increased significantly when pollen load was increased from 10 to 20 grains, but there was no significant correlation for an increase from 20 to 30 grains (Fig. A).
Fig. 3. The effects of pollen-load size (as indicated in the key) on floral closure and female fitness in female recipients (A) and perfect recipient pollinated with cross- (B) or self-pollen (C). Different letters indicate values significantly different at the (more ...)
For perfect recipient flowers, when pollinated with ten pollen grains, no floral closure occurred regardless of whether cross- or self-pollen grains were used. Twenty grains induced closure in 26·9 % of flowers that were cross-pollinated and in 36 % of flowers that were self-pollinated. Increasing the pollen load from 20 to 30 grains significantly increased PC in the cross-pollination group (Fig. B), but the increase was not significant in the self-pollination group (Fig. C). In both cross- and self-pollination groups, PD increased significantly with increasing pollen load as we had expected, but the differences in other indices (NF, PF, SN and SS) were not significant (Fig. B, C).
The effects of pollen type on floral closure and female fitness
When 20 grains were received, the proportion of closed flowers was higher in the self-pollination group than in the cross-pollination group (Fig. A), but the situation was reversed when 30 grains were received (Fig. B). However, the differences between the treatments were not significant (χ2 = 0·488, d.f. = 1, P = 0·485 for 20 grains; χ2 = 1·867, d.f. =1, P = 0·172 for 30 grains). At any given pollen-load size, there was no significant difference in NF, PF, SN or SS between cross- and self-pollinated flowers (Fig. A, B).
Fig. 4. The effects of pollen type on floral closure and female fitness when (A) 20 and (B) 30 pollen grains were received. There is no significant difference (at the 0·05 level) between cross- and self-pollination in any of these categories. PC, Proportion (more ...)
The effects of floral morph on floral closure and female fitness
At all three pollen-load sizes, female flowers showed a higher proportion of floral closure than did perfect flowers with cross-pollination (χ2 = 15·261, d.f. = 1, P < 0·001 for 10 grains; χ2 = 9·876, d.f. = 1, P = 0·002 for 20 grains), although this difference was not significant when 30 grains were received (χ2 = 2·468, d.f. = 1, P = 0·116) (Fig. A, B). Pollen density was not significantly influenced by floral morph, but female flowers had significantly higher NF, PF, SN and SS than did perfect flowers (with cross-pollination; Fig. A, B).
Fig. 5. The effect of floral morph on floral closure and female fitness when (A) 20 and (B) 30 pollen grains were received. ** indicates that there is a significant difference between the female recipient and the perfect recipient at the 0·01 level. PC, (more ...)
The differences in female fitness between closed and open flowers under the same condition
In general, closed flowers in both female and perfect recipients had higher female fitness than flowers that had not closed under the same condition, but the differences in most of the indices (PD, NF, SN and SS) were not significant across different pollen-load sizes (Table ). For female recipients, PF was the only index that was significantly different between closed and open flowers across all pollen-load sizes. When the results from all three pollen-load sizes were combined, we found that the lowest PF in closed flowers was still higher than the highest PF in open flowers (Table ). However, this applied only to female flowers, not to perfect flowers.
Comparison of female fitness (mean ± s.e.) between closed and open flowers at different pollen-load sizes (number of grains on the stigma), for different floral morphs (female and perfect flowers) and pollen types (cross- and self-pollen)
When the data were analysed using binary logistic regression, PF was the only index that predicted robustly across all pollen-load sizes whether floral closure would occur in female recipients (Table ). We failed to find such a predictor for perfect recipients (Table ).
Binary logistic regression examining the factors affecting floral closure in female flowers, at different pollen-load sizes (number of grains on the stigma)
Binary logistic regression examining the factors affecting floral closure in perfect flowers, with cross- or self-pollination, at different pollen-load sizes (number of grains oin the stigma)
Fitness consequences of floral closure under natural and manipulated conditions
Under natural pollination conditions, we collected 57 fruits from closed perfect flowers and 40 fruits from closed female flowers. The fruit set among these samples was higher in perfect flowers than in female flowers (0·53 vs. 0·40, χ2 = 5·89, d.f. = 1, P = 0·015). For fruits with seeds, the seed number per fruit was higher in perfect flowers (12·53 ± 1·45, n = 24) than in female flowers (8·06 ± 1·85, n = 16), but the difference was not significant (t = 1·857, d.f. = 44, P = 0·070).
All flowers that were hand-pollinated set fruit. Manipulation of flowers to prevent closure did not significantly influence seed production in either perfect or female flowers (for perfect recipients, 17·77 ± 2·03 seeds in manipulated flowers vs. 15·91 ± 1·81 in control, n = 22, t = 0·876, d.f. = 21, P = 0·391; for female recipients, 20·93 ± 1·75 in manipulated flowers vs. 22·33 ± 2·15 in control, n = 30, t = –0·365, d.f. = 29, P = 0·531). However, the difference between morphs was significant, with female flowers showing higher seed production than perfect flowers (t = 2·177, d.f. = 50, P = 0·034).