Photosynthetic acclimation to elevated CO2 is modified by source:sink balance in three component species of chalk grassland swards grown in a free air carbon dioxide enrichment (FACE) experiment

Artificial chalk grassland swards were exposed to either ambient air or air enriched to 600 ?mol mol–1 CO2, using free-air CO2 enrichment technology, and subjected to an 8 week simulated grazing regime. After 14 months of treatment, ribulose-1,5-bisphosphate carboxylase (Rubisco) activity (Vc,max) and electron transport mediated ribulose-1,5-bisphosphate (RuBP) regeneration capacity (Jmax), estimated from leaf gas exchange, were significantly lower in fully expanded leaves of Anthyllis vulneraria L. (a legume) and Sanguisorba minor Scop. grown in elevated CO2. After a change in source:sink balance brought about by defoliation, photosynthetic capacity was fully restored in A. vulneraria and S. minor, but acclimation continued in the grass Bromopsis erecta (Hudson) Fourr. Changes in net photosynthesis (Pn) with growth at elevated CO2 ranged from a 1·6% reduction in precut leaves of A. vulneraria to a 47·1% stimulation in postcut leaves of S. minor. Stomatal acclimation was observed in leaves of A. vulneraria (reduced stomatal density) and B. erecta (reduced stomatal conductance). The results are discussed in terms of whole-plant resource-use optimization and chalk grassland community competitive interactions at elevated CO2

Women's and Men's Work: The Production and Marketing of Fresh Food and Export Crops in Papua New Guinea

© 2019 Oceania Publications Fresh food markets have been a fixture of the social and economic landscape of urban and rural PNG since colonial times. They were often the first points of engagement with the market economy, especially for women, who as small-scale producers, sold surplus produce from their food gardens located on communally-owned land. Although local food markets have remained an important livelihood for women, the later adoption and expansion of perennial export cash crops like coffee and cocoa overshadowed food production for local markets as men dominated export crop production on land alienated from communal ownership for decades or permanently. New forms of social relations of production and more exclusive forms of land tenure emerged to accommodate export crop production that were very different from those governing the production and marketing of fresh food. Market values and a trend towards individualisation of production with less capacity to mobilise labour through reciprocal labour exchange networks have characterised export crop production. With the income benefits captured largely by men, women began redirecting their labour to fresh food production where they were able to exercise more control of production and income while still mobilising labour through indigenous labour exchange arrangements. Attempts by men to appropriate the income of women and sons’ labour in export cropping were greater during flush periods when income levels were high, and they were less likely to attempt to appropriate this income in low crop periods when incomes were lower. However, with the recent emergence of female entrepreneurers earning relatively large sums of money in large-scale, profit-driven vegetable production, the moral frameworks governing food production are coming to resemble those governing export crops, and making labour more difficult to mobilise. Despite women being key players in these changes, we argue there is an emerging risk that men will attempt to assert control over this income or move into vegetable production themselves and possibly marginalise women in the process