ene ▁gla ci ation ▁cycles , ▁which ▁were ▁the ▁dram atic ▁climate ▁changing ▁events ▁over ▁ 4 0 ▁thousand ▁years ▁ago . ▁ ▁P lo id y ▁D . ▁v erna ▁poss esses ▁the ▁characteristic ▁of ▁pol yp lo id y , ▁having ▁more ▁than ▁two ▁sets ▁of ▁chrom os om es . ▁When ▁there ▁is ▁a ▁me i otic ▁or ▁mit otic ▁error , ▁and ▁there ▁are ▁multiple ▁copies ▁of ▁the ▁gen ome . ▁Pol yp lo ids ▁form ▁at ▁reason ably ▁high ▁frequency ▁in ▁flow ering ▁plants , ▁suggesting ▁that ▁plants ▁have ▁a ▁remark ably ▁high ▁t endency ▁for ▁pol yp lo id y . ▁There ▁are ▁several ▁advantages ▁to ▁pol yp lo id y , ▁such ▁as , ▁observation ▁of ▁hy brid ▁vig or , ▁or ▁heter osis , ▁which ▁is ▁the ▁pol yp lo id ▁off spring ▁of ▁two ▁dip lo id ▁parents ▁is ▁more ▁vig orous ▁and ▁health y ▁than ▁either ▁of ▁the ▁two ▁dip lo id ▁parents . ▁Pol yp lo id y ▁is ▁a ▁class ▁of ▁mut ation ▁that ▁results ▁in ▁a ▁mit otic ▁dou bling ▁and ▁failure ▁in ▁cell ▁division . ▁It ▁appears ▁that ▁this ▁is ▁very ▁common ▁in ▁plants , ▁in ▁the ▁method ▁of ▁un redu ced ▁pol len . ▁Since ▁per enn ial ▁plants ▁are ▁able ▁to ▁under go ▁self ing ▁or ▁a sex ual ity ▁when ▁they ▁are ▁unable ▁to ▁find ▁a ▁mate , ▁it ▁appears ▁pol yp lo id y ▁is ▁more ▁common ▁in ▁the ▁per enn ial ▁species ▁of ▁plants