Pollen Germination and Tube Growth after Selfing and Crossing Coronilla varia L¹

Abstract

Crownvetch, Coronilla varia L., is relatively self‐incompatible. Plants selected to represent the full range of self‐fertility of a large sample of C. varia L. ‘Penngift’ were used in greenhouse experiments to locate the site or sites of incompatibility of self‐pollinations. Pollen germination and pollen tube growth in pistils after self‐ and cross‐pollinations were observed employing UV fluorescence microscopy.Pollen germination on the stigma and pollen tube penetration of the style occurred within the first 12 hours after self‐ and cross‐pollination. Pollen tubes reached ovaries within 24 hours for both types of pollination.In one experiment, the average number of germinated pollen grains on stigmas was significantly higher after crossing than after selling. However, this relationship between the two types of pollination was not consistent over the plants studied. For most plants, pollen germination on stigmas after cross‐pollination was about twice that after self‐pollination. This suggested that self‐incompatibility existed on the stigma. In the second experiment, using a different pollen source, the average number of germinated pollen grains on the stigma after crossing was not significantly different from that after selfing and the site of incompatibility seemed to be in the style.Pollen tube behavior in the ovary was the same for selfing and crossing in both experiments. For selfing, less ovules matured as seed than were penetrated by pollen tubes. Thus, both fertilization failure and post‐fertilization ovule abortion could have affected the amount of seed set after selling.Pollen germination and pollen tube behavior were the same in flowers from excised stems and stems growing on plants.

CONTROL BY THE EMBRYOSAC OVER POLLEN TUBE GROWTH IN THE STYLE OF THE AVOCADO (PERSEA AMERICANA MILL.)

“…In Coronilla varia for example, Baluch, Risius and 152 iV;i-M. SEDGLEY >V •.. Cleveland (1973) observed occasional instances where two tubes entered an ovule and Ter-avanesjan (1949) noted sixty to eighty tubes entering the ovary of a Gossypium hirsutum flower although only thirty ovules are generally present. On the other hand Ockendon and Gates (1975) observed a reduction in number of tubes reaching the ovary to a figure lower than the usual number of ovules in Brassica oleracea.…”

“…Pistils were collected 18 h after pollination and squashes stained with Aniline.Blue were prepared according to the method of Martin (1959) as modified by van Hal and Verhoeven (1968). (Preparations from pistils collected between 6 and 30 h after pollination did not differ from those taken after 18 h.) The preparations were observed using a Zeiss Photomicroscope II with reflected light from an HBO 100 high pressure mercury vapour lamp, BG3 exciter filter and 65/50 harrier filter comhination.…”

“…In a further fifty-three cases the styles with stigmas attached were removed and processed for fluorescence microscopy while the corresponding ovaries were processed for normal transmitted light microscopy and embedded in glycol methacrylate according to the method of Feder and O'Brien (1968). Serial 2.2^-nva thick longitudinal sections through the ovary were stained with periodic acid-Schiff stain and Toluidine Blue and observed with a Zeiss Photomicroscope II.…”

Pollen tube dynamics following half- and fully-compatible pollinations in self-compatible almond cultivars

“…However, Baluch et al (1973), working with Coronilla varia L., and Socías i Company (2001), studying almond, showed that pollen tube behaviour was the same under these conditions as in pistils of non-excised branches of potted plants or trees in the field. Moreover, this method allows one to work under controlled conditions (particularly important for temperature) for all cultivars during the assay.…”

Compatibility and incompatibility in witloof-chicory (Cichorium intybus L.). 3. Gametic competition after mixed pollinations and double pollinations

“…This may be caused by several phenomena such as an acceleration of growth rate of the slower pollen tubes in the basal part of the style, a retardation of growth of the rapid tubes or both, or differences in penetration capacities of the ovary, the ovule or the embryosac. Such different selective barriers have also been suggested in Coronillu (BALUCH et al, 1973). Maybe the self pollen and/or the foreign pollen send a signal downwards to basal parts of the style or the ovary to block or retard the passage of the first arriving pollen tubes (often from the self pollen) enabling the later arriving pollen tubes (often from the foreign pollen) to overcome the time handicap and to fuse with the egg-tel.…”