Match each example of outcrossing with the appropriate mechanism. A. In many gra
ID: 80119 • Letter: M
Question
Match each example of outcrossing with the appropriate mechanism. A. In many grasses, pollen will not geminate on the stigma if the S genotype of the pollen matches any S allele in the female tissue. B. Pine trees produce separate male and female cones or the same plant. C. In foxglove flowers, the anthers mature before the stigma becomes receptive. D. Hops plants produce male and female flowers on different plants. E. In some species of sweet potato, pollen will not germinate if the pollen parent had any S allele that matches any S allele in the female tissue.Explanation / Answer
A 1) In many grasses pollen will not germinate on the stogma, if the S genotype of the pollen matches any S allele in the female tissue.
2. Becuse S pollen tube growing in a pistile caryy S and S1 alleles. This produces S and S1 proteins in extracellaluar space this would inhibit the growth of pollen tube.
3. RNase activity of S protein would degrade pollen tube RNA leadning to the inhibition of tube growth.
B 1) Both male and female cones are on the same three but males cones located on the lower branches of the tree.
2. This prevent self pollination and promotes fertilization with other pine trees, which increases genetic variation among trees.
C 1) In foxglove anthers matures before the stigma becomes receptive. and older male flowers are lower than female flowers.
2. As plants depends on wind for pollination, pollen traveling upwards is verly low, which favors cross pollination.
D 1) Hops is monoecious plant that produce stamels and pistils in separate flowers of the same plant.
2. in this plant photoperiodic impulses mediate development of stamens and pistil separately.
3. This photoperiodic impulses will prevent self pollination and facilitates cross pollination.
E. 1. Once the egg is fertilized by male gamete, it triggers some mechanism so that it prevents the entry of other male gemetes to prevent second fertilization.
2. In this process S protein of pollen tube and S protein pistil matchs with parent pollent tube and facilates fertilization.
3. This prevents the growth of other pollent tube.