Ethylene Effects in Pea Stem Tissue

Abstract

The marked effects of ethylene on pea stem growth have been investigated. Low temperature and coichicine, both known microtubule depolymerization agents, reverse the effects of ethylene in straight growth tests. Low temperature (6 C) also profoundly reduces the effects of gas in terms of swelling, hook curvature, and horizontal nutation. Deuterium oxide, an agent capable of rigidifying microtubular structure, mimics the effects of ethylene. Electron microscopy shows that microtubule orientation is strikingly altered by ethylene. These findings indicate that some of the ethylene responses may be due to a stabilizing effect on microtubules in plant cells.The multinet hypothesis suggests that isodiametric expansion is prevented in normally elongating cells by radially oriented microfibrils in the cell wall (25). The finding that the orientation of microfibrils usually parallels that of microtubules (9, 21) has led to the suggestion that microtubules may be responsible for determining the orientation of newly deposited cellulose microfibrils (21, 23). Colchicine, which is known to alter microfibrillar deposition (12) and produce a mottled birefringence pattern (10), is also known to depolymerize microtubules (3, 12). On the other hand, D20 produces a banded birefringence pattern similar to that exhibited by C2H4-treated tissue (8) and is known to have a "stabilizing" effect on microtubules (13). were incubated for various times at 24 C in the light or dark. After the predetermined period of time, epicotyls were cut from the seed and shadow-graphed. Hook angles were measured with a protractor (16).Straight Growth Tests. Seeds were soaked as previously described, germinated in plastic bins containing moist vermiculite and grown in darkness at 24 C for 7 days. Under dim green light, 10-mm subhook sections were excised from the third internode of selected seedlings (plants whose third internode was less than 30 mm). Ten sections were floated in 10 ml standard growth media 12% sucrose, (w/v), 5 mm CoCl2, 5 mim phosphate buffer (pH 6.8), 1 mm IAA, and appropriate concentrations of colchicine and C2H4J in 125-ml Erlenmeyer flasks which were sealed with vaccine caps and gently shaken in the dark at 24 C for 12 h. In some experiments, some of the flasks were incubated for 48 h at 6 C. After incubation, C2H4 levels were determined by GC, stem sections were weighed on an analytical balance, and lengths were measured to the nearest 0.1 mm.Long Term Low Temperature Experiments. Pea seeds were surface-sterilized with a 5% Clorox solution, rinsed and soaked in sterile water for 6 h, and planted in moist vermiculite in autoclaved 1-liter glass jars. The jars were sealed with air-tight lids and appropriate concentrations of C2H4 were introduced. They were incubated at 6 C for up to 60 days in the dark. At 3-day intervals, the jars were ventilated and fresh C2H4 was introduced. Observations were made and pictures were taken periodically.

Ethylene-Induced Lateral Expansion in Etiolated Pea Stems

“…DISCUSSION Ethylene, colchicine, and DCB each affect a different aspect of cell wall synthesis but have essentially the same effect on the mode of expansion in excised pea internode sections. Ethylene treatment results in changes in the wall matrix (13,29) as well as a reorientation of cellulose microfibrils (1,9,12,21,26); in cortical cells, the predominant orientation of microfibrils changed from transverse to longitudinal after 5 h of treatment (12). Similar changes were seen in the orientation of wall-associated microtubules (12).…”

“…Ethylene is thought to affect the mode of growth by altering microtubule and cellulose microfibril orientation (1,9,12,21,26). Colchicine and other agents which affect microtubule and microfibril orientation also inhibit elongation and induce lateral expansion (6).…”

Cell Division and Expansion Growth during Rose Petal Development

“…Cortical microtubules have been proposed to regulate the orientation of cell expansion (Shibaoka et al, 1994). Ethylene inhibits longitudinal cell expansion and promotes lateral cell expansion, which is associated with changes in cortical microtubule orientation (Roberts et al, 1985;Steen and Chadwick, 1981). In some rose cultivars, ethylene accelerates flower opening (Reid et al, 1989;Tan et al, 2006) and treatment with silver thiosulfate complex suppresses petal reflection (Doi, 1995).…”

Two Leucine-Rich Repeat Receptor Kinases Mediate Signaling, Linking Cell Wall Biosynthesis and ACC Synthase in Arabidopsis

“…Ethylene has been shown to play a role in regulating anisotropic growth. In hypocotyls, ethylene inhibits elongation primarily by altering the orientation of cell elongation, which is correlated with a change in the orientation of the microtubules (Steen and Chadwick, 1981;Lang et al, 1982;Roberts et al, 1985;Takahashi et al, 2003). In the root, ethylene strongly inhibits root elongation, but radial expansion is only modestly increased and microtubules appear to be unaffected (Baskin and Williamson, 1992).…”