Gall-Insect Community on Big Sagebrush Varies With Plant Size but not Plant Age

2015 ◽  
Vol 44 (4) ◽  
pp. 1095-1100 ◽  
Author(s):  
Kayla A. Spawton ◽  
William C. Wetzel
2017 ◽  
Vol 107 (6) ◽  
pp. 768-776 ◽  
Author(s):  
C.I. Rodríguez-Álvarez ◽  
M. Muñiz ◽  
G. Nombela

AbstractWhitefly, Bemisia tabaci, is one of the most important pests of tomato, Solanum lycopersicum L. The Mi-1 gene mediates tomato resistance to the Middle East-Asia Minor 1 (MEAM1) and Mediterranean (MED) species of B. tabaci, three species of root-knot nematodes, Meloidogyne spp., and the potato aphid, Macrosiphum euphorbiae. Tomato seedlings bearing the Mi-1 gene are resistant to nematodes soon after germination but resistance to aphids is developmentally regulated; a reliable conclusion about Mi-1 resistance to B. tabaci was not available to date. In the present work, 3-, 5- and 8-week-old plants of the tomato cultivars Motelle and Moneymaker (bearing and lacking the Mi-1 gene, respectively) were simultaneously tested under free-choice (antixenosis) and no-choice (antibiosis) conditions, to assess the real influence of plant age on the Mi-1-mediated resistance to the MED species of B. tabaci. Subsequently, plants of the same age but with different level of development were compared to check whether the plant size can also affect this tomato resistance. Obtained results demonstrated that Mi-1-mediated resistance to B. tabaci is developmentally regulated, as variations in the age of bearing-Mi-1 plants affects most infestation parameters tested. Differences between cultivars with and without the Mi-1 gene were significant for 8- but not for 3-week-old plants. For 5-week-old plants, differences between cultivars were less pronounced than in older plants, expressing an intermediate level of resistance in Motelle. Plant size also influenced whitefly infestation and reproductive activity on the resistant cultivar. However, plant age has more impact than plant size on the Mi-1-mediated resistance of tomato to B. tabaci.


1983 ◽  
Vol 61 (10) ◽  
pp. 2581-2591 ◽  
Author(s):  
Sandra J. Newell

Demographic data were gathered on populations of Viola incognita Brainard, V. pallens (Banks) Brainard, and V. adunca Ait. in Newfoundland. Density, recruitment, and mortality varied within and among species; but most populations expanded tremendously during the 4-year study period. Increasing density in V. pallens and V. incognita populations resulted in decreasing mean size of ramets. Density effects on plant size in V. adunca were obscured by the addition of many small seedlings to the populations. Seedling density and survivorship were relatively high, and disturbance appears to play an important role in violet population dynamics. Relative plant age (i.e., cohort) and plant size seldom were associated with plant survival over a 1-year period. An association between plant size and survival existed in V. adunca only because one-leaf plants had a higher mortality rate than plants with two or more leaves. Low survivorship was associated with reproduction in V. incognita, but no such association existed in the other species. Levels of herbivory were low, and herbivory and subsequent survival over 1 year were not associated.


HortScience ◽  
1990 ◽  
Vol 25 (12) ◽  
pp. 1612-1613 ◽  
Author(s):  
Deborah A. Tolman ◽  
Alexander X. Niemiera ◽  
Robert D. Wright

Seedlings of 30-, 35, 40-, -45, and 50-day-old marigold (Tagetes erecta Big. `Inca Gold') in 500-ml plastic pots containing a 1 peat: 1 perlite (v/v) medium were treated with several fertilizer levels (N at 20, 50, 80, and 110 mg·liter-1); solution nutrient levels in the medium were determined 6 hours later. Older/larger container-grown plants absorbed more N, P, and K from the medium solution than younger/smaller plants. Also, older plants (>40 days) absorbed at least 88% of the solution N regardless of N treatment. Nitrogen absorption, regardless of plant age, increased as N application rates increased. The latter result implies that even though total N absorption increases with plant age/size, nutrient levels in the medium solution for optimal growth and nutrient uptake may be similar regardless of plant size.


2013 ◽  
Vol 14 (1) ◽  
pp. 60-70 ◽  
Author(s):  
R. P. Karrfalt ◽  
N. Shaw

2011 ◽  
Vol 12 (3) ◽  
pp. 263-267 ◽  
Author(s):  
R. D. Cox ◽  
L. H. Kosberg ◽  
N. L. Shaw ◽  
S. P. Hardegree

Author(s):  
Lyudmila Ashmarina

The directions and results of many years of research on the development and prevalence of diseases on perennial leguminous grasses (meadow clover, pannonian clover, sainfoin, sowing alfalfa) in Western Siberia are presented. A whole range of diseases was revealed, the intensity of development, which depends on weather conditions, resistance of varieties, plant age, etc.


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