Germination ecology of Leptochloa chinensis: a new weed in the Italian rice agro‐environment

Summary Leptochloachinensisisanewweedthathasbeenfoundwith increasing frequency in Italian rice paddies. Thegermination ecology of L. chinensis seeds was studiedin order to investigate the development mechanismsand survival strategy of this weed in rice paddies ofnorthern Italy. Leptochloa chinensis seeds showed nodormancy and exhibited germination even in anoxicconditions. Germination was strongly influenced bytemperature(minimumaround15 C;optimal25–35 C)and light (phytochrome dependent).Temperature fluc-tuation caused an increase of seed germination in thedark. Seed burial also strongly inhibited germinationandemergenceofthisspecies.At5cmseedburialonly5%ofseedlingsemergedinfloodedconditions,whileatthe same depth, but with no flooding, no seedlingemergence was observed. This phenomenon was notdue to oxygen depletion, as germination was notinhibited by complete anoxia, as demonstrated by thefact that some seedlings did emerge in floodingconditionswhenwaterwasnodeeperthan6cm.Seedburial and concomitant flooding induced an unusualgermination: first coleoptile emergence and subse-quently emergence of the radicle was observed. Thepossible exploitationof this knowledge for weedmanagementisdiscussed.Keywords: Leptochloa chinensis, germination ecology,emergence,aquaticweed,rice.

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