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Atkinson Christopher J. Policarpo Michaelangelo Webster Anthony D. Kuden Ayzin M. 《Plant and Soil》1999,206(2):223-235
The drought tolerance of the commercial apple ( Malus domestica Borkh.) rootstocks M9, M26, M27 and MM111, and some new selections
from the rootstock breeding programme at HRI-East Malling (AR69-7, AR295-6, AR360-19, AR486-1 and AR628-2), was assessed using
potted, glasshouse-grown, unworked rootstocks. After an initial period of growth under well-watered conditions the amount
of irrigation was gradually reduced, for some treatments, to simulate natural drying in the soil. At the end of a six-month
growth period, the rootstocks were harvested and the production of dry matter and its partitioning to various plant parts
determined. The rootstocks exhibited large differences in shoot and root dry matter, and root length but not all the rootstocks
showed declines in root mass or length in response to the droughting treatment. The dwarfing rootstocks tended to have smaller
amounts of both coarse (>2 mm diameter) and fine roots (<2 mm diameter), than the more vigorous rootstocks. Irrespective of
rootstock or irrigation treatment there was a close linear relationship between coarse and fine root. There was also no change
in the length/weight relationship for fine roots irrespective of rootstock or irrigation treatment, i.e. 42 m of fine root
weighed 1 g dry weight. In some cases the amount of root produced could be directly correlated with the rootstock known potential
to control scion vigour, but this was not true for all the rootstocks examined. The absence of this relationship was particularly
evident in some of the new selections of rootstock. The possible causes for these differences, compared with commercially
used rootstocks, is discussed in relation to the origin and parentage of the rootstock selections. Despite this lack of a
root length/vigour relationship, the amount of dry matter partitioned to shoot growth reflected the rootstocks' known vigour.
The different responses of these rootstocks to drought are discussed along with their implications for understanding the mechanisms
by which rootstocks are thought to dwarf scion shoots. 相似文献
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Michaelangelo Tabone Bard Ermentrout Brent Doiron 《Journal of theoretical biology》2010,266(3):391-5659
Proper pattern organization and reorganization are central problems facing many biological networks which thrive in fluctuating environments. However, in many cases the mechanisms that organize system activity oppose those that support behavioral flexibility. Thus, a balance between pattern organization and pattern flexibility is critically important for overall biological fitness. We study this balance in the foraging strategies of ant colonies exploiting food in dynamic environments. We present discrete time and space simulations of colony activity that uses a pheromone-based recruitment strategy biasing foraging towards a food source. After food relocation, the pheromone must evaporate sufficiently before foraging can shift colony attention to a new food source. The amount of food consumed within the dynamic environment depends non-monotonically on the pheromone evaporation time constant—with maximal consumption occurring at a time constant which balances trail formation and trail flexibility. A deterministic, ‘mean field’ model of pheromone and foragers on trails mimics our colony simulations. This reduced framework captures the essence of the flexibility-organization balance, and relates optimal pheromone evaporation to the timescale of the dynamic environment. We expect that the principles exposed in our study will generalize and motivate novel analysis across a broad range systems biology. 相似文献
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