ALBERT — All Library Books, journals and Electronic Records Telegrafenberg

Hits per page

hits 1 - 2 | 2 hits

Sorting

Electronic Resource

DNA endoreduplication in maize endosperm cells: the effect of exposure to short-term high temperature (2000)

Engelen-Eigles, G. ; Jones, R. J. ; Phillips, R. L.

Oxford, UK : Blackwell Science Ltd

Plant, cell & environment 23 (2000), S. 0

add to mindlist on the mindlist

Details

ISSN: 1365-3040

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: DNA endoreduplication in Zea mays L. (cv. A619 × W64A) endosperm peaks between 16 and 18 d after pollination (DAP). The physiological function of DNA endoreduplication is not known but it is believed to be important in maize kernel development. In the present study, we investigated how 2, 4 or 6 d of high temperature (35 °C) affected DNA endoreduplication and maize kernel development in comparison with control kernels grown at 25 °C. Data were collected on fresh weight (FW), nuclei number, mitotic index, and DNA endoreduplication. Maize endosperm FW and nuclei number were reduced by exposure to 4 or 6 d of high temperature. At 18 DAP, the 2 d high temperature treatment (HTT) caused a reduction in FW and nuclei number, but had no effect on DNA endoreduplication and average DNA content per endosperm. However, when the exposure to high temperature was increased to 4 or 6 d, FW, nuclei number and the magnitude of DNA endoreduplication were progressively reduced, and the peak mitotic index was delayed compared with the control endosperm. At 18 DAP, the 4 d treatment showed 54·7% of the cells were 3 or 6 C, whereas only 41·2% were 12 C or higher. Six days of high temperature also resulted in a reduction in endosperm FW, nuclei number and a delay in the peak of mitotic index. DNA endoreduplication occurred in the kernels exposed to this treatment, although the magnitude was severely reduced compared with the control kernels. Nuclear DNA content was highly correlated (r= 0·93) with kernel FW, suggesting an important role of DNA endoreduplication in determining endosperm FW. The data suggest that high temperature during endosperm cell division exerted negative effects on DNA endoreduplication by dramatically reducing the nuclei number, leaving fewer nuclei available for DNA endoreduplication. However, the data also suggest that prolonged exposure to high temperature restricts entry of mitotic cells into the endoreduplication phase of the cell cycle.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1365-3040.2000.00564.x

Permalink

	Location	Call Number	Expected	Availability

Others were also interested in ...

Paper (German National Licenses)

Fulltext

Electronic Resource

Supporting Timing Analysis by Automatic Bounding of Loop Iterations (2000)

Healy, Christopher ; Sjödin, Mikael ; Rustagi, Viresh ; [et al.]

Springer

Real-time systems 18 (2000), S. 129-156

add to mindlist on the mindlist

Details

ISSN: 1573-1383

Keywords: hard real-time systems ; worst-case execution time ; static analysis

Source: Springer Online Journal Archives 1860-2000

Topics: Computer Science

Notes: Abstract Static timing analyzers, which are used to analyze real-time systems, need to know the minimum and maximum number of iterations associated with each loop in a real-time program so accurate timing predictions can be obtained. This paper describes three complementary methods to support timing analysis by bounding the number of loop iterations. First, an algorithm is presented that determines the minimum and maximum number of iterations of loops with multiple exits. Even when the number of iterations cannot be exactly determined, it is desirable to know the lower and upper iteration bounds. Second, when the number of iterations is dependent on unknown values of variables, the user is asked to provide bounds for these variables. These bounds are used to determine the minimum and maximum number of iterations. Specifying the values of variables is less error prone than specifying the number of loop iterations directly. Finally, a method is given to tightly predict the execution time of inner loops whose number of iterations is dependent on counter variables of outer level loops. This is accomplished by formulating the total number of iterations of a loop in terms of summations and solving the resulting equation. These three methods have been successfully integrated in an existing timing analyzer that predicts the performance for optimized code on a machine that exploits caching and pipelining. The result is tighter timing analysis predictions and less work for the user.