PLASTIDS IN THE ROOTS OF PHASEOLUSVULGARIS

Abstract

SUMMARYIn roots of Phaseolus vulgaris plastid development takes place from the apical meristem both upwards into the root proper and downwards into the root cap. The maximum state of plastid development seems to be achieved in the cortical cells of that part of the primary root associated with mature root hairs. However in these cortical cell plastids the thylakoid system is very limited in extent and no true prolamellar bodies are formed. Farther from the apex of the root proper, in the zone of mature lateral roots, the plastids appear to have undergone dedifferentiation and to have lost whatever thylakoids they once contained.Both the rate of plastid development and the patterns of production of ancillary plastid structures, including starch and membrane-bound bodies, vary in different cell files. The differential distribution of these and other plastid features are summarized in the accompanying diagrams.

Globular structures in roots accumulate phosphorus to extremely high concentrations following phosphorus addition

“…The material inside the plastids appeared structured to some degree, and its appearance is consistent with the presence of protein, but not starch (e.g., see Sullivan & Gray, ) or lipids. The absence of membrane‐bound structures within the plastids is consistent with the roots being sectioned in the root hair zone (Whatley, ). The size and shape of the plastids observed with TEM cannot be directly compared with that of the globular structures identified using SEM due to the different methodologies required for sample preservation, imaging, and element analysis.…”

“…These include the up‐regulation of TSub_g9430.t1 and its high similarity to PHT4;1 and PHT4;4 (discussed below); the detection in root cortex cells, using TEM, of large plastids that did not contain substantial amounts of starch or lipids or a complex internal membrane structure; and, the globular shape, general structure, and presence of up to four globular structures per cell being inconsistent with them being nuclei. Root plastids are known to accumulate P (Mukherjee et al, ) as well as starch and protein (Newcomb, ; Whatley, ), and toxic compounds (Turnau, Kottke, & Oberwinkler, ).…”

Salinity induced structural changes in meristematic cells of barley roots

“…Whatley (1974Whatley ( , 1977 studied the development of plastids in the leaves of Phaseolus vulgaris and Zea mays and regarded the amoeboid form as a common intermediate in a sequence of five successive developmental stages in the transition from the proplastid state to a chloroplast (Thomson & Whatley, 1980). In roots, this transition was interpreted as a spatial sequence of differentiation of plastids along the axis of a root from its tip to more mature regions (Whatley, 1983 a;Whatley & Gunning, 1981). For example, within 1-5 mm from the junction of the meristematic region and root cap the plastids were mainly in the two early stages of dedifferentiated plastid and amyloplast (Whatley, 1983(3), while the third stage of amoeboid plastids prevailed in cells from about 1-5 mm to 4 mm from the junction of the meristematic region.…”

Stromules and the dynamic nature of plastid morphology

“…This theory was most comprehensively outlined by J. M. Whatley and colleagues. Whatley's group observed amoeboid plastids by EM in Phaseolus and a number of other species (Whatley, 1974, 1977, 1983a). Other groups observed amoeboid plastids in the scutellum of Triticum and Secale (O’Brien, 1951), leaves of Lilium and Convallaria (Steffen, 1964, as cited in Whatley, 1974), root tips of Phaseolus (Newcomb, 1967), leaves of Spinacia (Chaly et al ., 1980) and callus cultures of Vitis (Jasik & Hudak, 1987).…”