The Changes Of Phloem Structures And Callose Distributions During One Year Of Growth In Some Conifers

The changes of phloem structures and callose distributions during one year of growth innine conifers (Ginkgo biloba, Pseudolarix amabilis, Cupressus funebris, Sabina chinensis,Thuja occidentalis, Cunninghamia lanceolata, Taxodium distichum, Taxus chinensis, Torreyagrandis) were studied. The following conclusions were got:The arrangement of these nine conifers can be classified into three types: Pseudolarixamabilis is the Tsuga canadensis subtype in the Pseudotsuga taxifolia type; Ginkgo biloba,Taxus chinensis and Torreya grandis are the Ginkgo biloba type; Cupressus funebris, Sabinachinensis, Thuja occidentalis, Cunninghamia lanceolata, Taxodium distichum belong to theChamaecyparis pisifera type.There was a peak of cambium activities in Mid of July of Pseudolarix amabilis,Cupressus funebris, and Torreya grandis. In Mid of May and Mid of July, Thuja occidentalishad a peak activities of cambium, while that was End of May and Mid of September forTaxodium distichum. Sabina chinensis was strongly grown in April. The phloem ofPseudolarix amabilis was formed earlier than the xylem, while that of Sabina chinensis waslater than the xylem. Two tangential layers of phloem parenchyma cells of Pseudolarixamabilis were formed in this whole growth season. For Sabina chinensis and Thujaoccidentalis, a tangential layer of thick-walled phloem fibers may the beginning of thisseason's growth increment, and that of thin-walled phloem fibers may the end.Between Mid of June and Mid of July, new phellogen, derived from phloem parenchymacell and phloem ray parenchyma cell, was occurred in the secondary phloem of Thujaoccidentalis, Taxodium distichum. In the nonconducting phloem of Cupressus funebris,Sabina chinensis, Thuja occidentalis, Cunninghamia lanceolata, Taxodium distichum, Taxuschinensis and Torreya grandis, sieve cells were deformed by the enlarged phloem parenchymacells. When this part of phloem was separated from the living part, phloem parenchyma cellscollapsed and sieve cell mostly recovered and retained their original shape.`Using aniline blue staining and fluorescence microscopic observation. Two types ofcallose distribution was found; that is, broad distribution of callose in not only conductingphloem but also nonconducting phloem in Pseudolarix amabilis and Taxus chinensis, andlocalized distribution of callose in conducting phloem in Cunninghamia lanceolata, Cupressusfunebris, Ginkgo biloba, Sabina chinensis, Taxodium distichum, Thuja occidentalis, andTorreya grandis. The callose only occurred in the sieve areas of sieve cell. The seasonal distribution of callose in Taxodium distichum showed that it disappeared completely in theresting season and regenerated in active season with its increasing amounts in many rows ofsieve cells, which reflected the function of sieve cells in conducting phloem.