Question

Given figures show the pollen-stigma interaction, where pollen wall proteins are released onto the pellicle of stigmatic papillae, where recognition reaction occurs.

Which of the following statements drawn from given figures is incorrect?

• A. $P$ indicates compatible reaction in which the pollen tube penetrates the cuticle and grows down the papilla
• B. Development of callose plug between the plasma membrane and pectocellulosic layer of stigmatic papillae results in the incompatibility reaction in $Q$
• C. A callose plug which appears at the tip of pollen in $Q$, is dissolved by callase enzyme secreted by stigma resulting in compatibility reaction
• D. Deposition of callose can be employed as a reliable bioassay to detect compatibility or incompatibility reactions of pollen and stigma

Answer 1

Answer: (C)

Most studies on the physiology and biochemistry of intra-and interspecific incompatibility have highlighted the importance of the pollen wall and its protein contents in the pollen-stigma interaction. The most distinct response of the stigma to an incompatible pollen is the development of callose plug between the plasma membrane and pectocellulosic layer of the stigmatic papillae, just below the point of contact with , the pollen; a callose plug also appears at the tip of the pollen tube. With the appearance of the callose-plug the growth of the pollen tube ceases. The deposition of callose in the stigmatic cells can be employed as a reliable bioassay to detect incompatible pollen particularly where the rejection occurs on the stigma. This bioassay has served as a useful aid in providing direct evidence for the involvement of exine-borne proteins in incompatibility reaction.