ABSTRACT
The correlation between the amounts of carotenoids and azulenes and the arising of certain fluorescence maxima in pollen grains is also observed during the time that the pollen matures. In matured pollen, for example Philadelphus grandiflorus, the amount of carotenoids is higher, than in non matured ones, while azulenes are present, mainly in matured microspores. Maxima 510-520 nm (it is likely to be linked with carotenoids) and 620 nm (peculiar to azulenes) arise only in matured pollen. Pistils* A pistil is a structure, which consists of special pollen recognizing part known as a stigma, style and embryonal sac where the ovule is located. Abundant secretory ability is observed for a pistil stigma. The stigma of a pistil is a gland covered by specialized receptive cells able to recognize and to discriminate among pollen grains according to their genotype (Dumas et al., 1988). During interspecific matings it distinguishes “not self” i.e., pollen belonging to a species other than that of the pistil. This is generally rejected, for maintaining the stablility of the species. By contrast, in intraspecific mating, “non-self”, which corresponds to allopollen, is accepted, while self-pollen is rejected. This latter process enforces outbreeding and characterizes “the self-incompatibility phenomenon”. Photograph (Fig. 2.10) shows the fluorescence image of a pistil stigma and even of pollen grains lying on this stigma. After 2-5 min of the pollen addition (pollen from the same species) the fluorescence of the pistil surface increased significantly. It may be the response to the pollen from the same species. As will be shown in Chapter 5, the fluorescence intensity is also changed or not changed, if pollen grains from other species were applied to the pistil surface. Figures 2.11 and 2.12 demonstrate the use of microspectrofluorimetry which permits registering the fluorescence spectra of different parts of the pistil. Light emission along the pistil can be tested in detail, e.g. in tomato Lycopersicon esculentum (Fig. 2.11). The surface of the stigma has two maxima 460 and 525 or 595 nm (it depends on the degree of the opening of the pistil, the amount
