T,-H, 1994. The effect of H days oi niicroEravily on receneralion of inuicl plants (rom protoplasts, -Phvsiol. Plant, 92; 404^1 I,"The growih and development of protoplasts of rapeseed {Brii.\.\iia napu\ L. cv Line) and carrol (Daucus carora L, cv. Na\ona> were studied onboard the Space ShuUle 'Discovery' during an 8-da\ Internationa] Microgravity Laboraloiy (IML-1) mission in January !992. The flight e\pei'imenls were carried out in 'Biorack'. a fully controlled cell biological experimental facilit\. under microgravity conditions and in a l-;i,' centrifuge. Parallel experiments were performed in a 'Biorack' m(tdule on the ground. After retrieval, some samples \^ele subcultured on appropriate media and analysed for callus growih and regeneration to inlact plants. The remainder v\ere used for biochemical analysis. Samples fixed on board the Space Shuttle were kepi in 1 ^. f glutaraldehyde fixative al 4°C for ^-^ days for microscopy analysis after retrieval. Prcttctplasls expctsed to micrograviiy conditiitns showed u delay in cell wall synthesis. Cells were swctllen in appearance and fttrmed cell aggregates wilh (tnlv tew cells. Callus were obtained from protoplasts cultured under niicrograviu (FOg), (tn ihe !-.£,' cenlrifuge on board the shultle (Fig), under normal l-,i.' c(tndilions
Summary:
The phytotoxicity of glyphosate(N‐(phosphonomethyl glycine) to seedlings of white mustard (Sinapis alba) cultivated indoors was studied. Yellowing and wrinkling of leaves was observed, necrotic spots appeared and the elongation of the seedlings was significantly reduced at doses 0–49 kg ai/ha and above. Only when sprayed at 4–97 kg ai/ha was the effect of glyphosate 100% lethal (5–7 days after spraying) At the highest concentration of herbicide a marked decrease in chlorophyll content was found but with 0–49 kg ai/ha the chlorophyll content was found to be higher than that in the leaves of control plants.
Two and fourteen days after spraying with glyphosate and the commercial product samples of leaf and stem were harvested for electron microscopy. Cellular defects in the leaves ranging from slight swelling to complete disruption of the chloroplasts were detected at the two highest herbicide doses 48 h after spraying. These defects were intensified with time und in addition other sub‐morphological changes occurred: decrease in starch grain content, an increase in the number of dictyosomes and mitochondria, disruption of tonoplasts and increase of plastoglobuli In the more central parts of stem segments the commercial product resulted in greater cellular effects than did glyphosate. It is suggested that the differences may be due to the surfactant.
A simple method for electron microscopic preparation of plant protoplasts is described. The main problems in preparing these fragile protoplasts for electron microscopy have been cell collapse due to steep gradients between protoplasts and fixatives and unacceptable loss of material during the many steps of the procedure. These problems may be solved by immobilization of the protoplasts in calcium alginate beads. The free diffusion properties of this gel prevent steep gradients. The beads also simplify handling and prevent loss of material. Protoplasts isolated from hypocotyls of rape, Brassica napus (var. Niklas), have been used as a model system. Transmission electron microscopy of the immobilized protoplasts osmotically stabilized with glucose demonstrated adequate structural and ultrastructural preservation.
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