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#spores

14 public questions tagged with this topic.

Dictyostelium

Dictyostelium fruiting bodies primarily consist of:

Mature sorocarps consist of two cell types with opposite fates. Prestalk cells, after depositing cellulose tube, swell vacuoles, synthesize thick walls, and die, forming rigid stalk that supports sorus above substratum. Dead stalk provides mechanical strength and prevents desiccation without competing for germination resources. Spores remain alive, encapsulated, dehydrated, containing trehalose and heat-shock proteins for longevity. Structure composed of live stalk plus spores would collapse and consume nutrients. Therefore stalk sacrifice representing altruism illustrates kin selection where genetically identical cells benefit inclusive fitness by ensuring elevated dispersal of viable spores in fruiting structures.

Ref: Principles of Development, Lewis Wolpert, Chapter 3: Dictyostelium fruiting body - altruistic stalk cell death.

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Plant Classification

Thick spore walls in land plants mainly protect against

Land plant spores possess complex wall stratification including innermost intine cellulosic, middle exine rich in chemically inert sporopollenin highly resistant polymer derived from lipid metabolism, and outer perispore. Primary adaptive value involves preventing desiccation during prolonged airborne dispersal across dry air, fluctuating humidity and high temperatures, maintaining protoplast viability until germination on moist substrate. While sporopollenin confers resistance against pathogens, chemical degradation and UV, desiccation resistance drives major selection. Herbivory and mechanical damage affect larger vegetative organs, but microscopic spores chiefly face abiotic drying stress during colonization.

Ref: Wellman et al. Sporopollenin wall, J Micropalaeontology; Campbell Ch 29: Spore

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Plant Classification

Equisetum spores possess elaters which help in

Equisetum arvense and relatives, sole living genus of class Sphenopsida or Equisetopsida, produce homospore tetrads where each spore bears two hygroscopic ribbon-like elaters derived from outermost spore wall exosporium layer splitting spirally. Elaters uncoil under dry conditions and coil tightly when moist, causing spores to clump together improving wind dispersal as aggregates and promoting cross-fertilization between bisexual gametophytes on ground. They also provide slight locomotion on substrate surface toward moist microsites favoring germination. While not directly involved in fertilization or nutrition, elater movement enhances establishment.

Ref: Tryon & Lugardon 1991 Equisetum spores; Kramer & Green Fern Biology; Raven Ch 20

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