Some Features of the Shoot Systems in Representatives of the Tribe Sequoiae, Cultivated in Russia

The article focuses on the growth rates of three extant species belonging to the tribe Sequoiaceae: Metasequoia glyptostroboides, Sequoia sempervirens and Sequoiadendron giganteum. The material was collected from botanical garden collections on the Black Sea coast of the Caucasus and Crimea. During a long growing season, all three species form shoot systems of varying complexity: from unbranched shoots consisting of a single elementary shoot to sylleptically branched multi-axial systems. In S. giganteum, the shoot systems formed during an extra-bud growth period are similar to those of other Cupressaceae species and partly to those of Pinaceae. In Metasequoia glyptostroboides and Sequoia sempervirens, sylleptically branched shoot systems are differentiated into several variants: on orthotropic shoots in the upper part of the growth, plagiotropic branches are sylleptic and continue to grow after the orthotropic part of the shoot system has stopped growing. Plagiotropic sylleptic lateral shoots continue to branch into second-order lateral shoots. Similar structures are found in Araucaria and archaic fossil conifers. M. glyptostroboides and S. sempervirens have phyllomorphic branches of the same appearance as those described for Tsuga canadensis. Plagiotropic lateral sylleptic shoots continue to branch into second-order lateral shoots. Similar structures are known in Araucaria and fossil archaic conifers. M. glyptostroboides and S. sempervirens have phyllomorphic branches of the same appearance as described for Tsuga canadensis. These species are also characterized by buds formed serially below the sylleptically growing shoot. In M. glyptostroboides, the phyllomorphic branches fall off annually, and their perennial bases form a growing, basisympodially shortened shoot. The renewal bud is not located under the bark, as in Taxodium distichum.