SIEVE-ELEMENT PLASTIDS, NUCLEAR-CRYSTALS AND PHLOEM PROTEINS IN THE ZINGIBERALES

The sieve-element characters of 40 species from all families making up the monocotyledon order Zingiberales have been studied by transmissio n electron microscopy. While phloem-proteins are a typical component o f all eight families, the Zingiberaceae are characterized by nondisper sive protein bodies derived from nuclear crystals. The sieve-element p lastids are of the form-P2cs, i.e. contain cuneate protein crystals (a s typical of all monocotyledons) and starch grains, those of the famil y Musaceae have protein filaments in addition (form-P2cfs). The exclus iveness of the form-P2c(f)s plastids contributed to the homogeneity of the order and its distinctness among other monocotyledon taxa. When d iameters of the sieve-element plastids from leaf phloem are compared, in the ''banana group'' the family averages of the Strelitziaceae and the Lowiaceae have, respectively, maximum and minimum values and are c learly different from those in the Musaceae, the family in which they have been included previously. In the ''ginger group'', the family ave rages of the Zingiberaceae, Costaceae, and Marantaceae are close to th e order average, with only Cannaceae having minimum values. A comparis on of species averages, however, reduces the size differences between families: the value for Ravenala (Strelitziaceae) is close to those of the five Musaceae tested, and that of Globba (Zingiberaceae) even sli ghtly lower than the species average of Canna.