Effects of drought and subsequent rehydration on the structure, vitality, and permeability of Allium cepa adventitious roots

1993 ◽  
Vol 71 (5) ◽  
pp. 700-707 ◽  
Author(s):  
Elida Stasovski ◽  
Carol A. Peterson
Keyword(s):  
Allium Cepa ◽  
Lateral Root ◽  
Adventitious Roots ◽  
Free Water ◽  
Food Storage ◽  
Root Primordia ◽  
Root Cortex ◽  
Lateral Root Primordia ◽  
Allium Cepa L ◽  
Suberin Lamellae

Drought stress was induced in onion (Allium cepa L.) plants that had been sprouted from bulbs initially planted in moist vermiculite. The medium received no further water, and its free water content fell from 50 to 0% over a period of 35 d. The water stress thus imposed killed the root apices and accelerated the death of the epidermis. However, other regions, including the short cells of the dimorphic exodermis, the remainder of the cortex, and the stele (except for the mature vessels), remained alive for periods of prolonged drought (up to 200 d after cessation of watering). During this time, symplasmic continuity from the exodermis to the vascular tissues of the stele was maintained through the living cells as judged by the transport of fluorescein from an ambient solution into the stele. After the death of the epidermis, the presence of Casparian bands in all cells of the exodermis and suberin lamellae in its long cells presumably reduced the flow of water from the root to the dry external medium. A dieback pattern in which the cortex is retained would place an increased respiratory demand on the plant compared with dieback to the endodermis. However, this may be offset by positive functions such as preserving a site for future food storage and (or) providing a hospitable environment for mycorrhizae when conditions outside the root are hostile. Loss of a viable apex under conditions of drought induced the development of many lateral root primordia that did not emerge but remained dormant within the root cortex. When water was added to the growth medium, these grew out quickly and along with the new adventitious roots that sprouted from the bulbs, rejuvenated the root system. Stress periods longer than 200 d resulted in death of the majority of the roots, and the plants did not recover after watering. Key words: drought, roots, Allium cepa L., exodermis, hypodermis, dormant lateral root primordia.

Effect of naphthaleneacetic acid on the formation of lateral roots in the adventitious root of Allium cepa: number and arrangement of laterals along the parent root

1992 ◽  
Vol 70 (9) ◽  
pp. 1891-1896 ◽  
Author(s):  
Pedro G. Lloret ◽  
Antonio Pulgarín
Keyword(s):  
Allium Cepa ◽  
Adventitious Root ◽  
Lateral Root ◽  
Root Formation ◽  
Lateral Roots ◽  
Naphthaleneacetic Acid ◽  
Root Primordia ◽  
Sharp Rise ◽  
Allium Cepa L ◽  
Do So

The exogenous application of an auxin (α-naphthaleneacetic acid) to the adventitious root of Allium cepa L. promotes lateral root formation and inhibits main root elongation. If the adventitious roots are released from the influence of this auxin, they may resume elongation after 10−5 M but not after 10−4 treatment. Auxin leads to the appearance of late-forming root primordia intercalated between previously formed laterals. The arrangement of laterals along the adventitious root is another feature altered by treatment, i.e., control roots develop the same number of laterals throughout the length of the zone in which laterals appear, whereas in treated roots the number of laterals rises steadily as the distal end of this zone is approached. In 10−5 M auxin-treated roots, no increase in the number of laterals occurs in basal zones of the parent root, whereas treatment with 10−4 M naphthaleneacetic acid leads to a sharp rise in the number of laterals formed at these zones. Our results suggest that the basal part of onion roots is less sensitive than the apical portion of the effects of naphthaleneacetic acid. This chemical seems to have a rejuvenating effect on cells of the pericycle, enabling them to initiate lateral primordia when under normal conditions they would no do so. Key words: Allium cepa, auxin, lateral root, naphthaleneacetic acid, onion.

scholarly journals Protocol: a method to study the direct reprogramming of lateral root primordia to fertile shoots

Plant Methods ◽  
2016 ◽  
Vol 12 (1) ◽  
Author(s):  
Abdul Kareem ◽  
Dhanya Radhakrishnan ◽  
Xin Wang ◽  
Subhikshaa Bagavathiappan ◽  
Zankhana B. Trivedi ◽  
...  
Keyword(s):  
Lateral Root ◽  
Direct Reprogramming ◽  
Root Primordia ◽  
Lateral Root Primordia

scholarly journals Influence of 1-p-D-arabinofuranosylcytosine on mitotic activity of apical meristem of onion (Allium cepa L.) roots

2015 ◽  
Vol 47 (1–2) ◽  
pp. 173-187 ◽  
Author(s):  
M. Kuraś ◽  
A. Malinowska
Keyword(s):  
Mitotic Activity ◽  
Chromosome Aberration ◽  
Allium Cepa ◽  
Cytosine Arabinoside ◽  
Adventitious Roots ◽  
Apical Meristem ◽  
Allium Cepa L ◽  
Cells With Micronuclei

The influence of increasing cytosine arabinoside (ara-C) concentration (50, 100, 300 and 500 μg/ml) on the mitotic activity of the apical meristem of onion adventitious roots was investigated during 24-h incubation in ara-C and postincubation in water. Incubation in ara-C inhibits reversibly mitosis, the degree of inhibition being dependent on the concentration used. 50 μg/ml ara-C causes only a slight and transitional mitotic depression, while 100—500 μg/ml reduces the per cent of mitoses in various degrees after 12-h incubation whereas after 24 h all concentrations (100—500) reduce mitosis to the same level of about 2 per cent (80% inhibition). During postincubation in water there occurs after treatment with 100—500 μg/ml ara-C, a wave of highly synchronized mitoses with a peak after 12 h. The highest frequency of synchronized mitoses (60°/o) appeared in roots treated with 300 μg/ml ara-C. The main wave is preceded by a small one with a peak after 2-4 h of postincubation. This seems to be the consequence of phases S and G<sub>2</sub> inhibition by ara-C. It was found that under the influence of ara-C the per cent of mitoses with chromosome aberration and of cells with micronuclei increased only slightly.

scholarly journals Cell Death in Cells Overlying Lateral Root Primordia Facilitates Organ Growth in Arabidopsis

2020 ◽  
Vol 30 (3) ◽  
pp. 455-464.e7 ◽  
Author(s):  
Sacha Escamez ◽  
Domenique André ◽  
Bernadette Sztojka ◽  
Benjamin Bollhöner ◽  
Hardy Hall ◽  
...  
Keyword(s):  
Cell Death ◽  
Lateral Root ◽  
Root Primordia ◽  
Lateral Root Primordia ◽  
Organ Growth ◽  
In Cells

Development of cell wall modifications in the endodermis and exodermis of Allium cepa roots

2001 ◽  
Vol 79 (5) ◽  
pp. 621-634 ◽  
Author(s):  
Fengshan Ma ◽  
Carol A Peterson
Keyword(s):  
Electron Microscopy ◽  
Allium Cepa ◽  
Plasma Membranes ◽  
Casparian Bands ◽  
Transmission Electron ◽  
Allium Cepa L ◽  
Suberin Lamellae ◽  
Pit Field ◽  
Casparian Band ◽  
Suberin Lamella

The cytological events of wall modification in the endodermis and exodermis of Allium cepa L. roots were examined with fluorescence and transmission electron microscopy. In the endodermis, Casparian bands, suberin lamellae, and tertiary walls developed in succession. At the site of the future Casparian band, the plasma membrane was bound to the wall before deposition of detectable hydrophobic components in the radial wall. Suberin lamellae were deposited on the inner faces of the primary walls, first along the outer tangential walls and then the inner tangential walls. On both walls, segments of the lamellae were formed earlier in primary pit fields than at nonprimary pit field regions. Suberin lamellae then extended to the radial walls. When they reached the Casparian bands, the lamellae intruded between the bound plasma membranes and the walls, so that the cells' plasma membranes remained intact. In this way, suberin lamellae that were continuous around the cells were laid down. Later, tertiary walls were deposited internal to the suberin lamellae. None of the wall modifications interrupted the symplastic connections of the endodermis. During suberin lamella and tertiary wall formation, more dictyosomes and ER profiles appeared than during Casparian band development. In the exodermis, although Casparian bands were readily detected with fluorescence microscopy, they were rarely detected with electron microscopy. Suberin lamellae were formed in long cells severing their plasmodesmata. As in the endodermis, dictyosomes and ER were prominent during suberin lamella formation. Tertiary walls were not formed in the exodermis.Key words: Allium cepa, Casparian band, endodermis, exodermis, suberin lamella, ultrastructure.

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