Search

Copyright of Functional Ecology is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Gremmenia abietis (Dearn.) Crous (syn: Phacidium abietis) was originally described in North America to accommodate the species associated with snow blight of Abies and Pseudotsuga spp. In Japan, this species was first observed on the dead needles on Abies sachalinensis and Picea jezoensis var. jezoensis in 1969. However, the identity of Japanese species was unclear due to the lack of molecular data and the absence of anamorph description. In this study, we collected fresh specimens from various conifer species (A. sachalinensis, A. veitchii, Pic. jezoensis var. jezoensis, Pic. jezoensis var. hondoensis, Pinus koraiensis, and Pin. pumila) in Japan and revised the taxonomy based on morphological and phylogenetic analyses. Phylogenetic analyses based on nuc rDNA internal transcribed spacer ITS1-5.8S-ITS2 (ITS), nuc 28S rDNA (28S), and RNA polymerase II second largest subunit (RPB2) regions indicated that the species belongs to Phacidiaceae. Conidiomata formed in vitro produced pyriform, hyaline conidia without mucoid appendage, which distinguished the species from phylogenetically related genera. Consequently, we established Chionobium takahashii to accommodate the snow blight fungus in Japan. Further phylogenetic analyses also indicated that C. takahashii includes several distinct clades corresponding to the host genera (Abies, Picea, Pinus). Morphological differences among those clades were unclear, suggesting that C. takahashii may contain host-specific cryptic species. [ABSTRACT FROM AUTHOR]

Sap freeze--thaw events are a main determinant of the distribution of broad-leaved woody plants in cool regions but the effect in other climates remains unknown. We used cryoscanning electron microscopy to examine the differences in plant growth patterns based on seasonal variation in xylem water distribution in four broad-leaved species (one ring-porous and three diffuse-porous species) in a temperate region of Japan. Leaf fall was detected in November for the ring-porous species Maackia amurensis Rupr. et Maxim., although embolisms were detected in large earlywood vessels in January of the following year. The percentage of embolisms in latewood vessels varied significantly between years. By contrast, xylem embolisms in diffuse-porous species (deciduous and evergreen) were barely detectable during winter. In one evergreen species, embolisms and refilling were detected in some vessels during the growing season. Based on the variation in the number of freeze--thaw events among years in Asian monsoon forests, we infer that M. amurensis obtained no benefit from extending leaf phenology because of the occurrence of vessel embolisms in winter. On the other hand, the leaf phenologies of deciduous and evergreen diffuse-porous species were less constrained by winter embolisms. Maackia amurensis persists in cool temperate regions by limiting the photosynthetic period.Key words: broad-leaved tree, xylem, embolism, seasonal change, warm temperate zone.Le gel-degel de la seve constitue un determinant principal de la distribution des plantes ligneuses des regions froides, mais son effet sous d'autres conditions climatiques reste inconnu. Les auteurs ont utilise la cryomicroscopie electronique a balayage pour examiner les differences dans les patrons de croissance des vegetaux sur la base de la variation saisonniere de la distribution de l'eau du xyleme chez quatre especes de feuillus (une espece a pores a anneaux et trois especes a pores diffus) d'une region temperee du Japon. La chute des feuilles etait observee en novembre chez l'espece a pores a anneaux Maackia amurensis Rupr. et Maxim., meme si des embolies etaient detectees dans les gros vaisseaux du bois initial en janvier de l'annee suivante. Le pourcentage d'embolies des vaisseaux du bois final variait significativement d'une annee a l'autre. Par contre, les embolies du xyleme des especes a pores diffus (decidues et sempervirentes) etaient quasi indetectables durant l'hiver. Chez une espece sempervirente, les embolies et le remplissage etaient detectes dans certains vaisseaux durant la saison de croissance. Sur la base de la variation du nombre d'evenements gel--degel entre les annees dans les forets de mousson en Asie, les auteurs deduisent que M. amurensis ne tirait aucun benefice a prolonger la phenologie foliaire a cause de la survenue d'embolies des vaisseaux en hiver. D'un autre cote, la phenologie foliaire des especes decidues et sempervirentes a pores diffus est moins contrainte par les embolies de l'hiver. Maackia amurensis persiste dans les regions froides temperees en limitant ses periodes de photosynthese. [Traduit par la Redaction]Mots-cles : arbre feuillu, xyleme, embolie, changement saisonnier, zone de climat tempere tiede., IntroductionWater transport in woody plants is directly related to their growth patterns and adaptation. Although water in woody plants is transported through xylem conduits (tracheids and vessels), it is disrupted [...]