( Gametophytes ( then ( ( ( produce ( ( ( haploid gametes ) , ) ( which ( ( join ( with ( other gametes ) ) ) ( through fertilization ) ) ) ) ) ( to ( ( form ( diploid sporophytes ) ) ( once again ) ) ) ) . ) ) )
(ROOT (S (NP (NNS Gametophytes)) (ADVP (RB then)) (VP (VBP produce) (NP (NP (JJ haploid) (NNS gametes)) (, ,) (SBAR (WHNP (WDT which)) (S (VP (VBP join) (PP (IN with) (NP (JJ other) (NNS gametes))) (PP (IN through) (NP (NN fertilization))))))) (S (VP (TO to) (VP (VB form) (NP (JJ diploid) (NNS sporophytes)) (ADVP (RB once) (RB again)))))) (. .)))
Gametophytes then produce haploid gametes, which join with other gametes through fertilization to form diploid sporophytes once again.
(ROOT (S (NP (NP (JJ Sexual) (NN reproduction)) (PP (IN with) (NP (NNS gametes) (CC and) (NN fertilization)))) (VP (VBZ produces) (NP (JJ diploid) (NN sporophyte))) (. .)))