Function And Change Of GA₃ And ABA In The Viviparity Of Mangrove Plant Species

Viviparous mangrove plants,nonviviparous mangrove plants and nonviviparous nonmangrove plants are studied at their different development periods:flower-bud period,seed period,early germinating period and late germinating period.Possible viviparity mechanism is proposed and discussed by observing moisture content, contents and ratios of mineral elements(Na,K,Ca,Mg) and endogenetic hormones such as GA₃ and ABA.Results are showed as follow:1 Changes of endogenetic hormone contents in different development periods of progenitive organs of viviparous plants and nonviviparous mangrove species.(1) Change of GA₃ contents is similar in four developmental periods for viviparous mangrove species:it is decreasing from seed period to early germinating period and to late germinating period,except those in flower-bud period and late germinating period of Avicennia marina.Nonviviparous mangrove species-Xylocarpus Koenig has low ABA content during different developmental periods.However,nonviviparous nonmangrove plants show various kinds of changes and have lowest GA₃ content in seed period. Generally speaking,GA₃ contents in viviparous plants of seed period are higher than those in nonviviparous.(2) For viviparous mangrove species,ABA content changing has the same trend: highest in flower-bud period,lowest in seed period,increase after germination.Take Xylocarpus Koenig and Plumeria rubra as examples,ABA contents are highest in seed period,higher in early germinating period and decrease dramatically in late germinating period.Similar to viviparous mangrove species,ABA contents in Kopsia officinalis are lower than Xylocarpus granatum and Plumeria rubra and are high in flower-bud period and late germinating period instead of in seed period and early germinating period.(3) For viviparous plants,ratio of GA₃/ABA are highest in seed period and decrease in early germinating period,in which it is higher than flower-bud period and late germinating period.And ratio of GA₃/ABA shows no difference between flower-bud period and late germinating period.For nonviviparous plants,ratio of GA₃/ABA is low in the four periods s,ranging from 0 to 20,except that of Plumeria rubra seed in late germinating period. Comparing to Plumeria rubra and Kopsia officinalis,GA₃/ABA ratio of Xylocarpus granatum is low in all developmental periods excluding late germinating period.(4) In organs of remarkable viviparous species,GA₃ content decreases as follow: seed＞leave＞seed capsule.In the same way,nonviviparous nonmangrove plants have a decreasing order as:seed＞seed capsule＞leave.In organs of remarkable viviparous species,ABA content decreases as followed:leave＞seed＞seed capsule.In the same way,nonviviparous nonmangrove plants have a decreasing order:leave＞seed capsule＞seed.Moreover,leave has an ABA content which is much higher than seed capsule and seed.All leave and seed capsule in viviparous mangrove species have a GA₃ contents those are distinctive higher than those of nonviviparous plants,while their ABA contents are much lower.(5) For organs such as seed,seed capsule and leave,GA₃/ABA ratio is higher in viviparous plants than in nonviviparous.And it decreases as follow in four plants:seed＞seed capsule＞leave.Moreover,changes of hormone content are similar in viviparous and nonviviparous species.For nonviviparous plants, mangrove species Xylocarpus granatum has the lowest GA₃/ABA ratio.2 Changes of moisture contents in progenitive organs of viviparous plants and nonviviparous species.Water contents are distinctive between seed period and early germinating period. The highest moisture content is achieved by viviparous plants especially in seed period ranging from 60%to 80%.On the contrary,moisture contents of nonviviparous plants are low in seed(wither) period and early germinating period.3 Changes of mineral elements content in different developmental periods of progenitive organs of viviparous and nonviviparous species(1) Mangrove species have higher Na contents than nonmangrove plants during flower-bud period,seed period,early germinating period and late germinating period.(2) For viviparous mangrove species,K contents are high in early germinating period.On the other hand,nonmangrove plants do not have K contents which are distinctive from those of mangrove species during seed period,early germinating period and late germinating period.(3) The ratio of Na/K is less than 1 in viviparous and nonviviparous species, except those of Bruguiera gymnorrhiza in flower-bud period,seed period, and late germinating period and those of Kandelia candel and Avicennia marina in flower-bud period.Moreover,it is higher in viviparous species than that in nonviviparous plants during other developmental periods of progenitive organs,although it shows no distinctive difference between Xylocarpus granatum and viviparous species in early germinating period.(4) Ca content decreases as follow:remarkable-viviparous mangrove species＞latent-viviparous mangrove plants＞nonviviparous nonmangrove species. Similar to comparison group Kopsia officinalis and Plumeria rubra in comparable group,Ca content decreases with development of progenitive organs in viviparous mangrove plant Kandelia candeI and latent-viviparous mangrove plant Aricennia marina.But it increases with the development of progenitive organs in Bruguiera gymnorrhiza and Aegiceras corniculatum.(5) In each developmental period of progenitive organs,Na/Ca ratio of mangrove species is more than 1 except that of Bruguiera gymnorrhiza in early germinating period,while it is less than 1 in nonmangrove plants.(6) Viviparous plants have higher Mg²⁺ contents than those in nonviviparous species.Moreover,Mg²⁺ content decreases in remarkable-viviparous and latent-viviparous mangrove species from seed period to late germinating period.On the contrary,it increases in comparison group(Kopsia officinalis, Xylocarpus granatum,Plumeria rubra) from seed period to late germinating period.(7) For viviparous mangrove plants,contents of Na,K,Ca and Mg in seed capsule are higher than that in seed and other progenitive organs.On the contrary,contents of Na,K,Ca and Mg in seed capsules of nonviviparous species are lower than that in the seed.Except for the increasing Na content in early germinating period of Bruguiera gymnorrhiza,contents of Na,K,Ca and Mg in late germinating period of viviparous plants are lower than those in early germinating period.However,contents of Na,K,Ca and Mgin nonviviparous mangrove species are higher in late germinating period than those in early germinating period,except the content of Ca²⁺ in Plumeria rubra and the content of K⁺ in Kopsia officinalis...