Why are the seed cones of conifers so diverse at pollination?

Abstract

In wind-pollinated plants, morphological diversity may result from simple variation in development among lineages rather than selective pressures for any major differences in function or performance. This work also illustrates the broader importance of developmental context in understanding plant form and function relationships; because plant reproductive structures perform many different functions over their lifetime, subtle differences in development may dramatically alter the specific morphologies that they use to meet these demands.

The ontogeny of disparity in Cupressaceae seed cones

“…For example, other crown conifer lineages besides Cupressaceae appear to show similar morphological patterns, with mature seed cones composed of laminar imbricated scales (most Pinaceae and a few Podocarpaceae such as Pherosphaera ; Khan & Hill, 2021), polygonal interlocking scales (many Araucariaceae, extinct Cheirolepidiaceae, Sciadopitys ; see Stockey, 1982; Escapa et al ., 2012), or a combination of these forms ( Pinus cones have imbricated scales with expanded, polygonal apophyses; Farjon, 2021). The ontogenetic fitness landscape of conifers as a whole therefore appears similar to that of Cupressaceae, although more work is needed to characterize pollination‐stage disparity (see Losada & Leslie, 2018).…”

Pollen Germination and Pollen Tube Growth in Gymnosperms

“…Different pollination strategies are found in conifers [ 2 , 38 ]. Saccate pollen of Pinus and Picea floats on the surface of the pollination drop and with it is transferred to the nucellus, where it germinates.…”

“…It then germinates and forms a long tube that grows through the micropyle into the ovule and reaches the nucellus. The variety of patterns of pollen behavior in the female cone is extensively discussed in the literature, since it can provide important information about the evolution of pollination [ 2 , 20 , 22 ].…”

“…For example, the degree of gametophyte reduction varies, there are both zooidogamy and siphonogamy, and the reproductive process can both be relatively fast and last over several years. Botanical and evolutionary aspects, however, have already been described in sufficient detail in other reviews [ 1 , 2 , 3 , 4 ], whereas here we focus on the physiological data accumulated during the study of pollen germination in conifers; an informative overview of this topic was published in 2005 [ 5 ]. Here, we mainly consider new data accumulated over the past 16 years, as well as some important aspects that were outside the focus of the previous review.…”