BIOL 2242 Lecture Notes - Lecture 12: Sambucus, Cellular Differentiation, Parenchyma
5 Feb 2018
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Sambucus stem c. s. (p. 542) (spaces are channels through the tissue: living at maturity. Isodiametric (ball shaped, not long and tapered, similar in all dimensions) 25-80 micro (u) meters; look same in c. s. (cross section) and l. s. (lat. section: thin primary wall. Can develop secondary walls, lignify (rarely: large intercellular (between cells) spaces. Root parenchyma non photosynthetic, but active metabolism: storage. Both short and long term, in all organs: packing. Protect more fragile tissues e. g. as part of phloem: wound regeneration. 23. 6 transfer cell in sonchus leaf c. s. (p. 542): many wall ingrowths. Facilitates short distance solute transfer: various locations. In reproductive tissues e. g. embryo: stimulated by infection, called secretory cells in glandular structures. E. g. in floral nectaries and salt glands. 23. 7 collenchyma tissue in rheum petiole c. s. (fresh mount) (p. 543): living at maturity. %-15 micro (u) meters x 60 micro (u) meters; little vacuolation: non-tapered end walls. Remain plastic (stretchable) because non-lignified: stretch with growing shoot, non-elastic, location.
