Early development of the secretory cavity of peltate glands in Humulus lupulus L. (Cannabaceae).

Early development of the secretory cavity of chemically fixed peltate glands in Humulus lupulus L. showed secretions with different densities, light, gray and dark, in the cytoplasm of disc cells and in the periplasmic space adjacent to the developing secretory cavity. Secretions were detected in the disc cell wall and subsequently in the developing secretory cavity under the subcuticular wall of the sheath. Light and gray secretions in the cavity possessed a membrane-like surface feature. Secretions were in contact with the irregular inner surface of the cuticle. Secretions contributed to the thickening of the cuticle, whereas the membrane-like surface feature contributed to a network of Cannabis striae distributed throughout the cuticle. This study supports an early development and organization of the secretory cavity in H. lupulus, parallel to those in Cannabis, and may represent common features for lipophilic glands in angiosperms.

Plastid development in disc cells of glandular trichomes of Cannabis (Cannabaceae).

Plastids in lipophilic glandular trichomes of chemically fixed (CF) and high pressure cryofixed-cryosubstituted (HPC-CS) bracteal tissues of Cannabis were examined by transmission electron microscopy. In CF preparations, plastids in disc cells prior to secretory cavity formation possessed several lobed and dilated thylakoid-like features. In glands with secretory cavities, thylakoid-like features aggregated to form reticulate bodies that distended regions of the elongated plastids. Electron-gray inclusions evident on the plastid surface appeared continuous with the reticulate body. Inclusions of similar electron density also appeared in the cell cytoplasm, along the plasma membrane, between the plasma membrane and cell wall facing the cavity, and in the secretory cavity in both CF and HPC-CS preparations. The bilayer structure of membranes of the plastid envelope was evident in HPC-CS but not in CF preparations. In HPC-CS preparations, secretions were evident on the plastid surface and were continuous with those in the plastid through pores in the envelope. This study supports an interpretation that these specialized plastids, lipoplasts, synthesize secretions that are transported through the plasma membrane and cell wall to subsequently accumulate in the secretory cavity.

Dopamine biosynthesis at different stages of plant development in Papaver somniferum.

Latex and cell-free extracts of various organs and stages of plant and capsule development in Papaver somniferum, the opium poppy, synthesized dopamine, an alkaloid precursor, from 14C-dopa. The 1000 g X 30 min supernatant from latex of the pedicel-capsule junction converted more dopa than latex supernatant from the upper capsule or lower pedicel regions, although there was more protein in the latex from the capsule. Percent conversion of pedicel-capsule latex into dopamine was maximum in unopened flower buds and decreased within 14 days after flowering. Dopamine biosynthesis in latex and cell-free extracts also varied with the stage of organ development. Extracts from capsule tissue converted more labeled dopa into dopamine than did extracts from pedicels, leaves from vegetative plants at the rosette stage, leaves from flowering plants, or pedicels connected to capsules.

Interrelationships of glandular trichomes and cannabinoid content. II. Developing vegetative leaves of Cannabis sativa L. (Cannabaceae).

Gland number and cannabinoid content were quantified during ontogeny of vegetative leaves from three clones of Cannabis. Initiation of capitatesessile and bulbous glands was found to occur uniformly during leaf development. Cannabinoids were synthesized throughout leaf development as well, but at a decreasing rate. A positive correlation was found for total capitate-sessile glands per leaf as compared with total cannabinoid content of the leaf. The data also indicated that other leaf tissues in addition to the glands may contain cannabinoids.

Interrelationships of glandular trichomes and cannabinoid content. I: Developing pistillate bracts of Cannabis sativa L. (Cannabaceae).

Gland number and cannabinoid content for three clones of Cannabis were compared. Cannabinoid levels and mature glands were quantified throughout progressive stages of pistillate bract development in order to define possible interrelationships between glands and cannabinoids. Similar trends occurred among the clones for each gland type while individual cannabinoids displayed a different pattern in each clone. Gland initiation and development as well as cannabinoid synthesis were found to occur during bract ontogeny for all three clones. A positive correlation existed for the total number of capitate glands per bract compared to the total cannabinoid content of the bract. The study also suggested that the glands may contain the majority of the cannabinoids present in the bract.

Accumulation of non-utilizable starch in laticifers of Euphorbia heterophylla and E. myrsinites.

Starch biosynthesis and degradation was studied in seedlings and mature plants of Euphorbia heterophylla L. and E. myrsinites L. Mature embryos, which lack starch grains in the non-articulated laticifers, develop into seedlings that accumulate starch rapidly when grown either in the light or the dark. Starch accumulation in laticifers of dark-grown seedlings was ca. 47 and 43% of total starch in light-grown controls in E. heterophylla and E. myrsinites, respectively. In light-grown seedlings, starch was present in laticifers as well as parenchyma of stems and leaves, whereas in dark-grown seedlings starch synthesis was almost exclusively limited to laticifers. In 7-month-old plants placed into total darkness, the starch in chyma was depleted within 6 d, whereas starch in laticifers was not mobilized. The starch content of latex in plants during development of floral primordia, flowering, and subsequent fruit formation remained rather constant. The results indicate that laticifers in seedlings divert embryonal storage reserves to synthesize starch even under stress conditions (darkness) in contrast to other cells, and that starch accumulated in laticifers does not serve as a metabolic reserve. The laticifer in Euphorbia functions in the accumulation and storage of secondary metabolites yet retains the capacity to produce, but not utilize starch, a primary metabolite.

Laticifers in stamens of Papaver somniferum L.

Articulated anastomosing laticifers were identified at both light and electron microscopic levels in the stamens of Papaver somniferum L. They were observed associated with the phloem forming a continuous system from the filament into the anther of the stamen. Laticifers, which were comparable in structure to laticifers found elsewhere in the plant, possessed numerous vesicles of different sizes within the protoplast.