Environmentally controlled phenotypic plasticity of morphology and polypeptide expression in two populations of Daphnia pulex (Crustacea: cladocera)

Two local Daphnia pulex populations which are subject to different types of seasonally varying predation pressures were studied. Individuals from both populations were raised in laboratory environments which simulated either summer or winter temperatures and photoperiods. When individuals from the same parthenogenetic clone were raised in different seasonal environments, each clone exhibited phenotypic variation specific to each of the seasonal environments. Intraclonal phenotypic plasticity was found in both populations at two different levels: variation in morphological characters, and variation in the expressed polypeptide phenotypes. Summer environmental conditions induced predator-resistant morphological traits, while winter conditions induced predator-susceptible ones. From 65% to 71% of over 200 major polypeptides were specifically expressed in either one seasonal environment or the other. This is evidence for the existence of environmentally induced switching between alternate developmental programs. Clones from the population with the least year to year predictability of seasonal predation pressure showed more interclonal variation in environment specific phenotypic expression than clones from the more predictably fluctuating environment.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47754/1/442_2004_Article_BF00379879.pd

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Not AvailablePunjab is an agriculture intensive state where traditional rice-wheat cropping system has contributed towards food security of the nation. The productivity of this system has stagnated, even declined in certain areas due to depletion of native nutrient reserves and emergence of their defi ciencies, lowering of under-ground water table and resurgence of insects and diseases due to over exploitation. This has accentuated the need for diversifi cation from this system. Agroforestry has emerged as one of the viable alternatives for diversifi cation from existing rice-wheat rotation. Diff erent tree species are traditionally grown in the various agroclimatic zones of the state. The main tree species adopted by the farmers on their agriculture fi elds as block and boundary plantations are poplar, eucalyptus and dek. Appropriate tree species, their quality planting material and remunerative crop combinations have to be selected for higher returns. The productivity and economic returns from the agroforestry systems can also be increased by adopting the appropriate cultural and management practices.Not Availabl