The tropical rainforest mesocosm within the Biosphere 2 Laboratory, a model system of some 110 species developed over 12 years under controlled environmental conditions, has been subjected to a series of comparable drought experiments during 2000-2002. In each study, the mesocosm was subjected to a 4-6 week drought, with welldefined rainfall events before and after the treatment. Ecosystem CO 2 uptake rate ( A eco ) declined 32% in response to the drought, with changes occurring within days and being reversible within weeks, even though the deeper soil layers did not become significantly drier and leaf-level water status of most large trees was not greatly affected. The reduced A eco during the drought reflected both morphological and physiological responses. It is estimated that the drought-induced 32% reduction of A eco has three principal components: (1) leaf fall increased two-fold whereas leaf expansion growth of some canopy dominants declined to 60%, leading to a 10% decrease in foliage coverage of the canopy. This might be the main reason for the persistent reduction of A eco after rewatering. (2) The maximum photosynthetic electron transport rate at high light intensities in remaining leaves was reduced to 71% for three of the four species measured, even though no chronic photoinhibition occurred. (3) Stomata closed, leading to a reduced ecosystem water conductance to water vapour (33% of pre-drought values), which not only reduced ecosystem carbon uptake rate, but may also have implications for water and energy budgets of tropical ecosystems. Additionally, individual rainforest trees responded differently, expressing different levels of stress and stress avoiding mechanisms. This functional diversity renders the individual response heterogeneous and has fundamental implications to scale leaf level responses to ecosystem dynamics.Key-words : chlorophyll fluorescence; drought; leaf area; leaf fall; leaf growth; net ecosystem CO 2 exchange; photosynthesis; photosynthetic electron transport; tropical rainforest; tropical trees.Abbreviations : A eco , ecosystem photosynthetic CO 2 uptake rate ( m mol CO 2 m -2 s -1 ); c i , apparent intercellular CO 2 concentration (p.p.m.); ET, ecosystem evapotranspiration (mmol H 2 O m -2 s -1 ); ETR, photosynthetic electron transport rate ( m mol electrons m -2 s -1 ); F 0 , ground fluorescence of the dark-adapted leaf; F m , maximum fluorescence of the dark-adapted leaf; F , fluorescence of the light-adapted leaf; F m ¢ , maximum fluorescence of the light-adapted leaf; F v / F m , pre-dawn potential quantum yield of photosystem (PS) II (
In this paper we describe the very peculiar life-history2 of Chelonus texanus Cresson. In brief the adult Chelonus deposits its eggs in the eg!!;sof its hosts but the parasite emerges not from the egg, but from the larva developed therefrom. Oviposition in the host's egg' and retarded development of the parasite to permit the host to hatch and grow to considerable size has been pointed out by Marchal (Summarized by Bugnion, 1907. Smithsonian Report for 1906. pp. 310-314) with reference to the Encyrius fuscicollis Dalman which oviposits in the eggs of Hyponomeuia malinella, etc., and by Silvestri (Biologia del Liiomastix irt/llcaicUus (Dalm.). Portici, pp. 4, 5, 10. 1906) with reference to Litomastix iruncateUus Dalman. which oviposits in the eggs of Plusia gamma Limucus and other Lepidoptera .. Litomastix truncatellus is polyemhryonic and possibly prndogenetic in alternate generations; Encyrtus fuscicollis is also polyembryonic, hut the Chelonus we have observed is a single and simple parasite. The Litomastix adult measures only 1.9 mm: in length and the egg of Plusia measures 0.6 mm. in diameter. Chelonus measures fully 5 mm. and the eggs of Heliothis measure about 0.5 mm. in diameter, while those of Laphygma are still smaller. Thus the contrast is much more striking when one observes Chelonus ovipositing than it would be in observing Litomastix.
Unknown super. CatolacC'lLs hunteri-1 example. B"acon mellitor super. unknown-19. Calolaccus sp. super. Bracon mellitor-19. Catolaccus hunteri super. unknown-1 9. Calolaceus hunteri super. Bracon mellitor-19. CatolaCC'US incertus super. Bracon mellitor-2 9. Cerambyeolnus C'UShmanisuper. Braeon mellitor-8 0' (7), 99. Cerambycobius cyanieeps super. unknown-1 0'. Cerambycolnus cyanieeps super. Bracon mellitor-23 <3' (6), 28 9. Cerambyeolnus cyanieeps super. CatolaeC'lLs hunteri-2 <3' , 29. •Cerambycobius eyaniceps super. Catolaeeus incertus-1 r:l' , 3 '1. Eurytoma tylodermatis super. unknown-1 0' (3),29. Eurytoma tylodermatis super. Braeon mellitor-8 r:l' (2), 2 '1.
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