scholarly journals Movement of bristle precursors contributes to the spacing pattern in Drosophila

2002 ◽  
Vol 119 (2) ◽  
pp. 201-211 ◽  
Author(s):  
Olivier Renaud ◽  
Pat Simpson
Keyword(s):  
Development ◽  
1996 ◽  
Vol 122 (3) ◽  
pp. 997-1005 ◽  
Author(s):  
J.C. Larkin ◽  
N. Young ◽  
M. Prigge ◽  
M.D. Marks

Arabidopsis trichomes are single-celled epidermal hairs that serve as a useful model for the study of plant cell differentiation. An examination of the distribution of trichomes early in their development revealed that developing trichomes occur adjacent to another trichome much less frequently than would be expected by chance. Clonal analysis of epidermal cell lineages ruled out a role for cell lineage in generating the observed minimum-distance spacing pattern. Taken together, these results are consistent with a role for lateral inhibition in the control of trichome development. We also report the identification of a new locus, Reduced Trichome Number (RTN), which affects the initiation of trichomes. This locus was initially detected by the reduced number of leaf trichomes on Landsberg erecta plants compared to that on Columbia plants. Quantitative Trait Locus mapping revealed that more than 73% of the variation in trichome number was due to a major locus near erecta on chromosome 2. The reduced number of trichomes conditioned by the Landsberg erecta allele of this locus appeared to be due to an early cessation of trichome initiation. The implications of these observations are discussed with regard to previously published models of trichome development.


1969 ◽  
Vol 29 (2) ◽  
pp. 407-413 ◽  
Author(s):  
Merrill F. Elias

The relationship between pattern area and pattern discrimination learning was explored. The possibly confounding effects of pattern spacing, height, contiguity, and manipulation were removed or controlled by: (a) presenting illuminated .25-, 1-, and 4-sq. in. patterns in a totally dark room, (b) alternating correct and incorrect patterns in a randomly determined temporal succession, (c) equating pattern height for all pattern-area conditions, (d) prohibiting pattern manipulation. Increasing pattern height from 1 to 4 sq. in. still resulted in improved learning. Results were interpreted in terms of utilization of brightness and/or size differences as cues to pattern discrimination.


Mammal Study ◽  
2003 ◽  
Vol 28 (2) ◽  
pp. 121-128 ◽  
Author(s):  
Toru Suzuki ◽  
Toshiki Aoi ◽  
Koji Maekawa

Author(s):  
Kateřina Houšková ◽  
Oldřich Mauer

Quality of the above-ground part of European beech planted at different densities and spacing patterns for the purpose of artificial forest regeneration was monitored 3, 4 and 6 years after planting. The initial numbers of beech transplants were 5,000 pcs.ha−1, 10,000 pcs.ha−1, 15,000 pcs.ha−1 and 20,000 pcs.ha−1. The spacing pattern of transplants was either square or rectangular nearly in all variants: 1.4 × 1.4 m, 2 × 1 m, 1 × 1 m, 0.8 × 0.8 m, 1 ×0.65 m, 0.7 × 0.7 m and 1 × 0.5 m. Conclusions following out from the research are as follows: 1. neither the chosen density of transplants nor their spacing pattern had an essential influence on the after-planting loss or damage of trees; 2. through the planting of larger-diameter transplants it is possible to achieve canopy closure more rapidly as well as faster growth of the plantation; these beech plants keep the edge in growth and quality even 6 years after planting; 3. the higher is the beech plantation density, the less individuals occur in such a plantation with inappropriate stem form; 4. beech plants of the worst quality were found on plots with the lowest initial density of transplants (5,000 and 10,000 pcs.ha−1), yet the number of promising trees was sufficient even there. Thus, none of the experimental numbers of transplants per hectare or spacing arrangements of the European beech transplants can be claimed as inappropriate; however, further monitoring of the plots is necessary.


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