Study Of Pla3 Mutant On Young Panical Development Of Rice

In the progress from vegetative growth to reproductive growth of rice, differentiate to panicle promordium meristem is one of the most important developing phases, many genes like RID1、LHD2、LAX was indentified to affect this progress. PLASTOCHRON3 (PLA3) is a gene found recently and the mutant cannot earing normally. In order to study the characteristics of young panical development of pla3, we observed the appearance and cellular morphology of shoot apical meristem (SAM) by stereoscropic microscope, electron scanning microscope and paraffins sectioning. Following results was got:(1) Pla3 mutant is differ from normal rice. Differentiation of bract primordium happened in the first stage, branch primordium happened in the second stage, bract hair and floret primordium happened in the third stage, branch and floret observably grow in the fourth stage of young panical development of wild-type. However, pla3 mutant SAM can differentiate into young panical, brunch primordium and bract hair-liked structure was seen during young panical development, but brunch primordiums will differentiate into leafy primordiums and new plants instead of keep growing.(2) In the process of development of spikelets in normal rice, the end of branches differentiate into empty glume primordium, outer and inner glume primordium, pistils and stamens primordium in sequence, secondary sporogenous cells in anthers could be seen in phase four.This progress cannot be seen when PLASTOCHRON3 was deleted, because brunch primordium can not differentiate into spikelet primordium.(3) PLA3 affected the vascular bundles during young panicle development. Study to vascular bundles shows that the number of them is less on higher position of the main branch in wild-type, big vascular bundles in stem nodes could adjust their growth by segregation and recombination.What is more, some fibrous tissues were found which could restrict the growth derection to playing a role of regulatory effect in the growth of vascular bundles. In pla3 mutant, Two big vessels can be seen in an vascular bundle, which is much less than in wild type, and most vascular bundles grow in reverse direction when reached neck-panical and doesn’t access to young panical, which could be one of the reasons why panical developmentare aberrant.