Takayoshi Nishio

Cloning and functional analysis of the K+ transporter, PhaHAK2, from salt-sensitive and salt-tolerant reed plants

We isolated PhaHAK2 cDNAs from salt-tolerant and salt-sensitive reed plants. PhaHAK2 belongs to group II by phylogenetic analysis, and was predicted to be a high-affinity plasma membrane K+ transporter. Yeast transformed with the PhaHAK2-u from salt-sensitive reed plants (Phragmites australis) had a decreased ability to take up K+ in the presence of NaCl and showed a higher Na+ permeability than yeast transformed with PhaHAK2-n or PhaHAK2-e from two salt-tolerant reed plants. These results suggest a possibility that the continuous K+ uptake by PhaHAK2 and maintenance of high K+/Na+ ratio under salt stress condition is one of the causes of the salt-tolerance in reed plants.

High-affinity K+ transporter PhaHAK5 is expressed only in salt-sensitive reed plants and shows Na+ permeability under NaCl stress

To understand the mechanism of ion homeostasis in salt tolerant and sensitive plants, we isolated cDNAs for K+ transporter PhaHAK1-u and PhaHAK5-u from reed plants. PhaHAK1-u belongs to group I and PhaHAK5-u belongs to group IV by phylogenetic analysis, respectively. PhaHAK5-u is predicted to be a plasma membrane transporter, and shows high-affinity K+ transporter. Expression of PhaHAK5 was found in salt-sensitive reed plants, but not in any parts of salt-tolerant reed plants maintained under both control and K+ starvation conditions. Under the NaCl stress, the K+ uptake ability of the yeast strain expressing PhaHAK5-u was remarkably lower than that of the yeast strain expressing PhaHAK1-u, and PhaHAK5-u showed Na+ permeability. These results suggest that PhaHAK5 is one of the routes by which Na+ enters cells.

Phytosociology ofFagus hayatae forests in Taiwan

We aimed to clarify the floristic composition and phytosociological characteristics of beech (Fagus hayatae) forests in Taiwan. An attempt was also made to compare the flora of theF. hayatae forest and adjacent evergreen forests and/or Japanese beech (F. crenata) forests using information from previous phytosociological studies.F. hayatae forests are confined to a small part of north-eastern Taiwan. Thus, sampling sites were designed to cover all the knownF. hayatae forests. A total of 23 relevés were sampled and 163 species were recorded. The number of common species betweenF. hayatae forests and other forest ecosystems such as lower evergreen forests and Japanese forests were compared. Adjacent evergreen, broad-leaved forests in Taiwan consist of 29 common species withF. hayatae forests, while 57 component species ofF. hayatae forest were found common with the Japanese forests. A vegetation table was developed and one association (Yushanio-Fagetum hayatae Suzuki T. 1954, ex Hukusimaet al. 2004), with two subassociations and four variants were identified. In addition, a higher phytosociological unit was defined, in which the alliance Fagion hayatae Suzuki T. ex Hukusimaet al., the order Fagetalia hayatae nov.; and the class Fagetea crenatae Miyawaki, Ohba et Murase, 1964 were identified and/or proposed.F. hayatae forests in Taiwan distribute mainly on the summit and ridge part of the north-eastern mountains and were considered relict forest.RiassuntoLa presente ricerca ha lo scopo di chiarire i problemi riguardanti composizione floristica e caratteristiche fitosociologiche delle foreste di faggio (Fagus hayatae) a Taiwan. Viene inoltre presenta la comparazione di questa foresta con le foreste sempreverdi adiacenti e/o con le foreste del faggio giapponese (F. crenata), sulla base di informazioni derivanti da studi precedenti. Le foreste diF. hayatae sono confinate in un’area ristretta nel nordest di Taiwan. Pertanto, i siti campionati sono stati distribuiti in modo da rappresentare tutti i boschi diF. hayatae conosciuti. Sono stati eseguiti 23 rilievi, nei quali sono state identificate 163 specie. Nella comparazione viene indicato il numero di specie in comune tra la foresta diF. hayatae ed altri ecosistemi forestali, come foreste di bassa quota dell’isola e foreste di faggio del Giappone. La vegetazione adiacente in Taiwan è formata da foreste sempreverdi, che presentano 29 specie in comune con la foresta diF. hayatae; 57 specie della foresta diF. hayatae sono presenti anche nelle faggete del Giappone. I rilievi sono riuniti in tabella e sulla base di questa viene descritta un’associazione (Yushanio-Fagetum hayatae Suzuki T. 1954, ex Hukusimaet al. 2004), nella quale sono distinte due subassociazioni e quattro varianti. Inoltre, viene definito lo schema delle unità superiori, nel quale viene proposto che l’alleanza Fagion hayatae Suzuki T. ex Hukusimaet al., e l’ordine Fagetalia hayatae nov. siano inclusi nella classe Fagetea crenatae Miyawaki, Ohba et Murase, 1964. Le foreste diF. hayatae sono distribuite nella fascia sommitale e sulla cresta dell’area montana di nordest, ed hanno caratteristiche di vegetazione relitta.

Phytosociology of the Beech ( Fagus ) Forests in East Asia

Speciation of beech (genus Fagus) in East Asia has been intensive and beech forests are widely, though disjunctly, distributed within Japan, Korea, China and Taiwan. Beech forests lie between the evergreen broad-leaved forests in the south (lower limit) and the evergreen coniferous trees in the north (upper limit), making them a key vegetation type in East Asia. In this study, to better distinguish the features of beech forests in East Asia, we compared species composition of beech forests based on the known releves and on new releves we carried out in the field. As a result of that comparison, we were able to divide the beech forests of East Asia into three classes. Classes I and II are characterized by the abundance of deciduous flora. These 2 classes contain 4 orders, 8 alliances, 20 associations and 48 subassociations. Class III is composed of evergreen broad-leaved forest with the presence of Fagus. There are few common species among the classes, especially in China. Because of that, it is hard to describe the similarities and differences of plant communities only considering the species level. For that reason, we further compared also the genus and family composition, which were considered to have larger distribution between the different vegetation types. East Asian beech forests are characterized by genera endemic to East Asia, as well as by genera common to beech forests of the northern hemisphere. Classes I and II show a large overlapping in genus composition. Within each order, there are many characteristic genera, a fact that confirms the independence of each order. In contrast, few characteristic genera are found at the alliance level, although the frequency of genera within each alliance varies. That is not the case, however, in the association and the subassociation levels. We also compared life form composition for each vegetation unit. We found the following: (1) beech forests in East Asia always contain scrub bamboo species; (2) classes I and II contain evergreen conifers of PEN and NPEN life forms. Class I contains proportionally more deciduous flora, classified as life forms of PD, NPD, H scap and H rosul. Class III, in contrast, contains proportionally more evergreen flora, classified as life forms of PE, NPE and G rhiz. Class II contains an intermediate proportion of deciduous and evergreen floras. At the order level, the frequency of life forms for shrub and herb species is characteristic. At the alliance level there is much less difference in life form composition within each alliance. At both the alliance level and the order level, when the proportion of life forms indicative of broad-leaved forests is higher, the proportion of herbaceous life forms is lower. There are no significant differences in life form composition within each association and subassociation; a comparison of life form compositions within the lower vegetation units would not, therefore, be useful.

Syntaxonomy of the East Asiatic Fagus) Forests

Table 3.1 is a synoptic table of the forests dominated by the genus Fagus in East Asia. According to Table 3.1, the phytosociological system of beech forests in East Asia was classified as in Table 3.9 and the distribution map of the classified classes, orders, alliances and associations was depicted as Fig. 2.1. In Table 3.1, 68 species categorized as the species group 49 are the common species occurring in the beech forests in East Asia, although there is a regional bias. Many of the 68 species are character species of beech forests in each region.