Read the following points:a. Diclinyb. Dichogamyc. Self – incompatibilityd. HeterostylyThe above contrivances prevent

Dicliny (Unisexuality) : A device to prevent self pollination is the production of unisexual flowers. Presence of unisexual flowers confirm cross-pollination. Self pollination never takes place in these flowers. Examples – Date palm, Papaya (Carica).Dichogamy : In many bisexual flowers of the plants, stamens and carpels of a flower do not mature at the same time. In these plants pollen release and stigma receptivity are not synchronised. Either the pollen is released before the stigma becomes receptive or stigma becomes receptive much before the release of pollen.Heterostyly :There is difference in between the length of the filaments of stamens and length of style in flowers of some plants. Some of the plants having long stamens and short style, and some of the plants bear long style and short stamens, because anther and stigma are placed in different positions so that the pollen can not come in contact with the stigma of same flower.Self sterility or self incompatibility or intraspecific incompatibility : This is a genetic mechanism and prevents self pollen (from the same flower or other flower of the same plant) from fertilising the ovules by inhibiting pollen germination or pollen tube growth in the pistil.