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“Other” specialized structures

“Other” specialized structures. tubers tuberous roots rhizomes pseudobulbs. Propagation of “Irish” potato ( Solanum tuberosum ) tubers. conventional method: tuber is cut into sections, with an “eye” or node included; tubers used for propagation are called “seed” potatoes

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“Other” specialized structures

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  1. “Other” specialized structures • tubers • tuberous roots • rhizomes • pseudobulbs

  2. Propagation of “Irish” potato (Solanum tuberosum) tubers • conventional method: tuber is cut into sections, with an “eye” or node included; tubers used for propagation are called “seed” potatoes • micropropagation: veg. buds are excised, grown, multiplied in culture, handled to produce “microtubers” for virus-indexed “seed” stock • potato tubers are modified stems

  3. Fig. 15-15 and 15-16. Propagation of “Irish” potatoes by tuber pieces.

  4. Propagation by tuberous roots • Sweet potato (Ipomoea batatas) • adventitious shoots develop on the fleshy root • new “slips” are covered with soil, develop adventitious roots • Dahlia • plants are dug in the fall, divided • ea. divided section contains a tuberous root and a piece of the crown with a shoot bud

  5. Fig. 15-18. Propagation of sweetpotato by adventitious shoots from tuberous roots.

  6. Fig. 15-19. Propagation of dahlia by tuberous roots.

  7. Figure of dahlia tuberous root division, showing the “right” way and the “wrong” way (Free 1957)

  8. Rhizomes • Defn: specialized stem with the main axis of the plant growing horizontally at or below the ground surface • Types • Pachymorph: a short, thick, fleshy clump, determinate (terminating in a flowering shoot), e.g., German iris • Leptomorph: a slender stem with long internodes, indeterminate (growing continuously from the terminal apex); e.g., lily-of-the-valley)

  9. Fig. 15-20 and 15-22. Photo and figure showing pachymorph and leptomorph rhizomes

  10. Division of rhizomes • pachymorphs – rhizome sections are cut off, transplanted • leptomorphs - lateral offshoots (1st or 2nd yr) or pips (3rd-yr shoots) removed and transplanted • culm cuttings - culm (aerial flowering shoot) is laid horizontally, branches arise at the nodes (e.g., bamboo)

  11. Pseudobulbs • Defn: specialized storage structure of epiphytic orchids • Propagation methods • offshoots develop at the nodes of a long, jointed pseudobulb (e.g., Dendrobium) • rhizome division (Cattleya), cut back from the terminal end to include 4-5 pseudobulbs in each section • micropropagation

  12. Fig. 15-24. Cattleya orchid rhizome with several attached pseudobulbs.

  13. Micropropagation of orchids • disinfestation and plating of a shoot tip • formation of a “protocorm” • multiple shoots develop from protocorms • shoots are separated, rooted, transplanted to soil

  14. Fig. 18-11 and figure from Bhojwani (1983). Steps in the micropropagation of orchids.

  15. Recap • Tubers and tuberous roots • Rhizomes - types and propagation methods • Pseudobulbs and protocorms - propagation methods for orchids • And, from the text (Ch. 15): Who discovered that orchids could be vegetatively propagated by protocorms?

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