Public-Private Partnerships and Undernutrition: Examples and Future Prospects

In this chapter, we clarify what is meant by public-private partnerships (PPPs), provide examples of both successful and less successful PPPs and describe some broad lessons. We see scope for PPPs that would reduce aspects of undernutrition. However, this optimism comes with significant caveats. First, while there would appear to be a large body of evidence on this topic, closer examination shows that there are few independent, rigorous assessments of the impact of commercial sector engagement in nutrition. Considerable caution is therefore warranted when assessing either commendations or criticisms of PPPs in nutrition. Second, progress in this area requires that the private sector recognize that past and current actions by some firms have created an environment of mistrust and that the public sector accept that sustainable PPPs permit private firms to generate profits. Progress also requires recognition that PPPs involving multiple firms can be problematic either because such partnerships force competitors to collaborate or because they create the potential for the involved firms to lock out firms that are not members of the partnership. Lest this all sound too negative, from a nutrition perspective, we note that there may be significant scope for the involvement of the private sector in driving innovations that could reduce undernutrition. More speculatively, there may also be scope for the private sector to act as a financier of investments to improve children's nutritional status. For PPPs to succeed, there must be open discussions of the objectives, roles and expectations of all parties along with potential conflicts of interest.

Understanding the Rapid Reduction of Undernutrition in Nepal, 2001-2011

South Asia has long been synonymous with unusually high rates of undernutrition. In the past decade, however, Nepal has arguably achieved the fastest recorded decline in child stunting in the world and has done so in the midst of civil war and post-conflict political instability. Given recent interest in reducing undernutrition–particularly the role of nutrition-sensitive policies–this paper aims to quantitatively understand this surprising success story by analyzing the 2001, 2006, and 2011 rounds of Nepal’s Demographic Health Surveys. To do so, we construct models of the intermediate determinants of child and maternal nutritional change and then decompose predicted changes in nutrition outcomes over time. We identify four broad drivers of change: asset accumulation, health and nutrition interventions, maternal educational gains, and improvements in sanitation. Many of these changes were clearly influenced by policy decisions, including increased public investments in health and education and community-led health and sanitation campaigns. Other factors, such as rapid growth in migration-based remittances, are more a reflection of household responses to changing political and economic circumstances.

What determines adult cognitive skills? Influences of pre-school, school, and post-school experiences in Guatemala

Most empirical investigations of the effects of cognitive skills assume that they are produced by schooling. Drawing on longitudinal data to estimate production functions for adult verbal and nonverbal cognitive skills, we find that: (1) School attainment has a significant and substantial effect on adult verbal cognitive skills but not on adult nonverbal cognitive skills; and (2) Pre-school and post-school experiences also have substantial positive significant effects on adult cognitive skills. Pre-school experiences captured by height for age at 6 years substantially and significantly increase adult nonverbal cognitive skills, even after controlling for school attainment. Post-school tenure in skilled jobs has significant positive effects on both types of cognitive skills. The findings (1) reinforce the importance of early life investments; (2) support the importance of childhood nutrition ("Flynn effect") and work complexity in explaining increases in nonverbal cognitive skills; (3) call into question interpretations of studies reporting productivity impacts of cognitive skills that do not control for endogeneity; and (4) point to limitations in using adult school attainment alone to represent human capital.

Adult consequences of growth failure in early childhood

BACKGROUND

Growth failure is associated with adverse consequences, but studies need to control adequately for confounding.

OBJECTIVE

We related height-for-age z scores (HAZs) and stunting at age 24 mo to adult human capital, marriage, fertility, health, and economic outcomes.

DESIGN

In 2002-2004, we collected data from 1338 Guatemalan adults (aged 25-42 y) who were studied as children in 1969-1977. We used instrumental variable regression to correct for estimation bias and adjusted for potentially confounding factors.

RESULTS

A 1-SD increase in HAZ was associated with more schooling (0.78 grades) and higher test scores for reading and nonverbal cognitive skills (0.28 and 0.25 SDs, respectively), characteristics of marriage partners (1.39 y older, 1.02 grade more schooling, and 1.01 cm taller) and, for women, a higher age at first birth (0.77 y) and fewer number of pregnancies and children (0.63 and 0.43, respectively). A 1-SD increase in HAZ was associated with increased household per capita expenditure (21%) and a lower probability of living in poverty (10 percentage points). Conversely, being stunted at 2 y was associated with less schooling, a lower test performance, a lower household per capita expenditure, and an increased probability of living in poverty. For women, stunting was associated with a lower age at first birth and higher number of pregnancies and children. There was little relation between either HAZ or stunting and adult health.

CONCLUSION

Growth failure in early life has profound adverse consequences over the life course on human, social, and economic capital.

The economic rationale for investing in stunting reduction

This paper outlines the economic rationale for investments that reduce stunting. We present a framework that illustrates the functional consequences of stunting in the 1000 days after conception throughout the life cycle: from childhood through to old age. We summarize the key empirical literature around each of the links in the life cycle, highlighting gaps in knowledge where they exist. We construct credible estimates of benefit-cost ratios for a plausible set of nutritional interventions to reduce stunting. There are considerable challenges in doing so that we document. We assume an uplift in income of 11% due to the prevention of one fifth of stunting and a 5% discount rate of future benefit streams. Our estimates of the country-specific benefit-cost ratios for investments that reduce stunting in 17 high-burden countries range from 3.6 (DRC) to 48 (Indonesia) with a median value of 18 (Bangladesh). Mindful that these results hinge on a number of assumptions, they compare favourably with other investments for which public funds compete.

Parental Resources, Schooling Achievements, and Gender Schooling Gaps: Evidence of Change over 25 years in Rural Guatemala

We use village census data and linear regression models to examine changes between 1975 and 2002 in the associations of parental resources with boys' and girls' schooling in four rural Guatemalan villages. Levels of schooling in 1975 were universally low for children 7-17 years. Large increases in schooling achievements occurred between 1975 and 2002. By 2002, schooling levels were comparable for younger boys and girls (7-12 years, N = 3,525) and favored older boys compared to older girls (13-17 years, N = 2,440) by about 0.5 grades. The associations of household standard of living and maternal schooling with schooling among girls diminished over time and became more comparable with these associations among boys, and the associations of household standard of living with schooling among older boys declined and became more comparable with these associations among girls. Thus, as increased social investments reduce the costs of schooling or increase the supply and quality of schooling to families, the magnitudes of the associations between parental resources and children's schooling decline and become more gender equitable at all ages. However, our results show that older boys may benefit more than older girls from social investments in schooling. These changes suggest potential needs to monitor gender gaps in schooling retention among older children, to insure gender equitable access to social investments in schooling, and to encourage parents to invest in schooling as joint measures to achieve greater schooling achievements of girls and boys.

Disability and self-rated health among older women and men in rural Guatemala: the role of obesity and chronic conditions

Unprecedented population aging in poorer settings is coinciding with the rapid spread of obesity and other chronic conditions. These conditions predict disability and poor self-rated health and often are more prevalent in women than men. Thus, gender gaps in obesity and other chronic conditions may account for older women's greater disability and worse self-rated health in poor, rural populations, where aging, obesity, and chronic conditions are rapidly emerging. In a survey of 604 adults 50 years and older in rural Guatemala, we assessed whether gender gaps in obesity and other chronic conditions accounted for gender gaps in disability and self-rated health. Obesity strongly predicted gross mobility (GM) disability, and the number of chronic conditions strongly predicted all outcomes, especially in women. Controlling for gender gaps in body-mass index (BMI) and especially the number of chronic conditions eliminated gender gaps in GM disability, and controlling for gender gaps in the number of chronic conditions eliminated gender gaps in self-rated health. We recommend conducting longitudinal cohort studies to explore interventions that may mitigate adult obesity and chronic conditions among poor, rural older adults. Such interventions also may reduce gender gaps in later-life disability and self-rated health.

Individual capital and cognitive ageing in Guatemala

Using data from adults 50 years and older in Guatemala (N = 643), we assessed to what extent measures of individual capital-economic, social, intellectual, and biological-were associated with and account for variation in cognitive functioning, as measured by the Modified Mini-Mental Status Exam (M-MMSE). Measures of these components of individual capital are positively associated with cognitive functioning, and together with other attributes, account for 29.6 per cent of its variance. Schooling accounts for the largest unique share (5.3 per cent) of the variance, followed by household standard of living (2.0 per cent), church attendance (1.3 per cent), and z-score for height (0.9 per cent). In a setting like Guatemala-with low schooling, widespread poverty, malnutrition, and infectious disease-early life investments that increase schooling and improve nutrition may be valuable as investments to mitigate cognitive impairment in older adults and its contribution to the disease burden.

Nutritional supplementation in girls influences the growth of their children: prospective study in Guatemala

BACKGROUND

Better early childhood nutrition improves schooling, adult health, skills, and wages, but there is little evidence regarding its effect on the next generation.

OBJECTIVE

We assessed whether nutritional supplementation in children aged <7 to 15 y affected their children's nutritional status 29-38 y later.

DESIGN

We studied 791 children 0-12 y who were offspring of 401 Guatemalan women who had participated as children in a nutritional supplementation trial in which 2 villages were randomly assigned to receive a nutritious supplement (atole) and 2 were assigned to receive a less-nutritious supplement (fresco). We compared anthropometric indicators between the offspring of mothers exposed to atole and the offspring of mothers exposed to fresco.

RESULTS

Compared with the offspring of women exposed to fresco, the offspring of women exposed to atole had a 116-g (95% CI: 17, 215 g) higher birth weight, were 1.3-cm (0.4, 2.2 cm) taller, had a 0.6-cm (0.4, 0.9 cm) greater head circumference, had a 0.26 (0.09, 0.43) greater height-for-age z score, and had a 0.20 (0.02, 0.39) greater weight-for-age z score. The association for height differed by offspring sex. Sons of women exposed to atole were 2.0-cm (95% CI: 1.0, 3.1 cm) taller than the sons of women exposed to fresco. Supplementation was not associated with 6 other offspring anthropometric indicators that reflect measures of adiposity. Supplementation in boys did not affect their children's anthropometric measures.

CONCLUSION

Nutritional supplementation in girls is associated with substantial increases in their offsprings' (more for sons) birth weight, height, head circumference, height-for-age z score, and weight-for-age z score.

Height for age increased while body mass index for age remained stable between 1968 and 2007 among Guatemalan children

Promotion of optimal growth while preventing the emergence of obesity in childhood requires an understanding of the dynamics over time of linear growth and weight for height. To assess long-term secular trends in height-for-age and BMI for age in children <6 y old, we analyzed a series of cross-sectional surveys conducted between 1968 and 2007 in 4 villages in eastern Guatemala. We used height and weight of children <6 y old (n = 507, 606, 627, 704, 526, and 502 for survey years 1968, 1972, 1977, 1988, 1997, and 2005-7, respectively) to compute height-for-age Z-score (HAZ) and BMI-for-age Z-score (BMIZ) based on WHO growth standards. HAZ was -2.73 +/- 1.12 (mean +/- SD) in 1968 and -1.16 +/- 1.16 in 2005-7 (P < 0.001). The prevalence of stunting (HAZ <-2.0) was 73.0% in 1968 and 23.1% in 2005-7 (P < 0.001). Among children 57-63 mo old, HAZ in 2005-7 was 1.20 (95% CI, 0.79, 1.62) SD units higher than in 1968, corresponding to 5.6 cm in boys and 5.7 cm in girls. For all survey years except 2007, BMIZ increased through age 36 mo, then declined; for the 2005-7 sample, BMIZ did not vary by age. The prevalence of BMIZ >1.00 was 21.1% in 1968 and 19.6% in 2005-7 (P > 0.05); for BMI <-1.00, the respective prevalences were 7.9% and 5.2% (P > 0.05). There have been long-term improvements in child growth, as measured by HAZ, without concurrent increases in BMI over successive generations of children.

Effect of a nutrition intervention during early childhood on economic productivity in Guatemalan adults

BACKGROUND

Substantial, but indirect, evidence suggests that improving nutrition in early childhood in developing countries is a long-term economic investment. We investigated the direct effect of a nutrition intervention in early childhood on adult economic productivity.

METHODS

We obtained economic data from 1424 Guatemalan individuals (aged 25-42 years) between 2002 and 2004. They accounted for 60% of the 2392 children (aged 0-7 years) who had been enrolled in a nutrition intervention study during 1969-77. In this initial study, two villages were randomly assigned a nutritious supplement (atole) for all children and two villages a less nutritious one (fresco). We estimated annual income, hours worked, and average hourly wages from all economic activities. We used linear regression models, adjusting for potentially confounding factors, to assess the relation between economic variables and exposure to atole or fresco at specific ages between birth and 7 years.

FINDINGS

Exposure to atole before, but not after, age 3 years was associated with higher hourly wages, but only for men. For exposure to atole from 0 to 2 years, the increase was US$0.67 per hour (95% CI 0.16-1.17), which meant a 46% increase in average wages. There was a non-significant tendency for hours worked to be reduced and for annual incomes to be greater for those exposed to atole from 0 to 2 years.

INTERPRETATION

Improving nutrition in early childhood led to substantial increases in wage rates for men, which suggests that investments in early childhood nutrition can be long-term drivers of economic growth.

Economic and nutritional analyses offer substantial synergies for understanding human nutrition

There is growing recognition that interventions designed to improve human nutritional status have, in addition to their intrinsic value, instrumental value in terms of economic outcomes. In many cases, productivity gains alone provide sufficient economic returns to justify investments using benefit and cost criteria. The often-held belief that nutrition programs are welfare interventions that divert resources that could be better used in other ways to raise national incomes is incorrect. Many investments in nutrition are in fact very good economic investments. This recognition has developed out of work that integrates insights from nutrition and economics. Further exploration of this interface is the focus of this article, which seeks: 1) to outline recent contributions that integrate research results from both economics and nutrition, particularly in the context of poor countries; and 2) to describe some areas in which enhanced collaboration is likely to have substantial payoffs in terms of both improved knowledge and more informed policy choices. Collaborative cross-disciplinary research on the topics described here is likely to have substantial payoffs, not only in terms of our understanding of nutritional and economic issues, but also in the improved design of programs and policies that seek to benefit nutritional-related outcomes.

Physical activity level, dietary habits, and alcohol and tobacco use among young Guatemalan adults

Physical activity, diet, and alcohol and tobacco use are all related to the development of obesity, diabetes, coronary heart disease, osteoporosis, and cancer. We examined the distribution of measures of these behaviors in a cohort of individuals born in four villages in Guatemala between 1962 and 1977 and who were 26-41 years old in 2003. Response rates to the instruments averaged 80% of cohort members known to be living in Guatemala. Physical activity levels were moderate, and were lowest among migrants to Guatemala City. Dietary habits reflect early phases of the nutrition transition, with high carbohydrate and moderate fat intakes. Migrants to Guatemala City reported higher intakes of meat and of dairy products, while those remaining in or near the original study villages reported higher consumption of tortillas and of vegetables and fruits. One-third of men reported consuming alcohol and 42% were current smokers. Very few women reported alcohol or tobacco use.

Physical fitness, body composition, blood pressure, and blood metabolic profile among young Guatemalan adults

We assessed the distribution of several risk factors related to health: muscular strength (handgrip strength), cardiovascular endurance (step test), flexibility (sit and reach test), anthropometry and body composition, blood pressure, fasting plasma glucose, lipid profile, and hemoglobin in a cohort of Guatemalan adults who were born in four rural villages between 1962 and 1977. By 2002 approximately 32% had migrated to Guatemala City or elsewhere in the country. Men are more physically fit and leaner than women. Fatness, poor physical fitness, and metabolic syndrome are highly prevalent in women living in both rural and urban areas. Risk profiles worsen with increasing age. Men who migrated to Guatemala City have lower physical fitness, greater fatness and systolic blood pressure, and worse lipid profile than men who still live in their original villages. Such a pattern was not evident in women, except that blood pressure was higher in urban women than in women who lived in their original villages.

Validity of rapid estimates of household wealth and income for health surveys in rural Africa

STUDY OBJECTIVE

To test the validity of proxy measures of household wealth and income that can be readily implemented in health surveys in rural Africa.

DESIGN

Data are drawn from four different integrated household surveys. The assumptions underlying the choice of wealth proxy are described, and correlations with the true value are assessed in two different settings. The expenditure proxy is developed and then tested for replicability in two independent datasets representing the same population.

SETTING

Rural areas of Mali, Malawi, and Côte d'Ivoire (two national surveys).

PARTICIPANTS

Random sample of rural households in each setting (n=275, 707, 910, and 856, respectively).

MAIN RESULTS

In both Mali and Malawi, the wealth proxy correlated highly (r>/=0.74) with the more complex monetary value method. For rural areas of Côte d'Ivoire, it was possible to generate a list of just 10 expenditure items, the values of which when summed correlated highly with expenditures on all items combined (r=0.74, development dataset, r=0. 72, validation dataset). Total household expenditure is an accepted alternative to household income in developing country settings.

CONCLUSIONS

It is feasible to approximate both household wealth and expenditures in rural African settings without dramatically lengthening questionnaires that have a primary focus on health outcomes.

The influence of light quality and carbon dioxide enrichment on the growth and physiology of seedlings of three conifer species. I. Growth responses

Plant growth responds to light quality, as evaluated by the red/far-red (R/FR) quantum flux ratio, and to the level of CO2. Pinus banksiana, Picea mariana and Picea glauca seedlings were raised at 350, 700, or 1050 μL∙L−1 CO2 and high or low R/FR ratios and growth was measured over a 16-week growth period. Far-red rich light enhanced the whole plant and height relative growth rates of Pinus banksiana. The three species showed species specific responses in plant organ relative growth rates and partitioning ratios. On the basis of their biomass partitioning the species would be ranked Pinus banksiana < Picea mariana < Picea glauca for shade tolerance. In commercial operations, seedlings grown for outplanting are selected, in part, on the basis of plant form as described by the stem height/diameter ratio. More desirable ratios were obtained at ambient CO2 concentrations for Pinus banksiana and Picea mariana in red rich light and for Picea glauca in far-red rich light. Keywords: seedling growth, light quality, CO2 enrichment.

The influence of light quality and carbon dioxide enrichment on the growth and physiology of seedlings of three conifer species. II. Physiological responses

Pinus banksiana, Picea mariana, and Picea glauca were grown at 350, 700, or 1050 μL∙L−1 CO2 and either high or low red/far-red quantum flux ratios. After a 16-week, long day growth period, seedlings were subjected sequentially to short daylengths, then short days with low temperatures. Various physiological parameters were determined at the end of each treatment phase to monitor how those treatments influenced the onset of seedling dormancy. After the long day treatments, high ratios increased the total chlorophyll content and reduced the original level of chlorophyll fluorescence and the shoot total nonstructural carbohydrate content in very shade-intolerant Pinus banksiana. In shade-tolerant Picea mariana, high CO2 levels caused the main effects on these parameters while neither light quality or CO2 had significant effects on them in shade-tolerant Picea glauca. Short days and low temperature induced a proportional increase in the partitioning of total nonstructural carbohydrate to the roots in all species and produced other species and treatment-specific responses. Keywords: light quality, CO2 enrichment, chlorophyll fluorescence.

The influence of aluminum on growth, carbohydrate, and organic acid content of an aluminum-tolerant and an aluminun-sensitive cultivar of wheat

An aluminum-sensitive cultivar (Katepwa) and an aluminum-tolerant experimental line (PT741) of Triticum aestivum were grown in nutrient solutions containing 0–400 μM aluminum at pH 4.5. After 18 days of growth, plant fresh weight was reduced in the Al-sensitive and Al-tolerant germ plasm by as little as 100 and 200 μM Al, respectively, and a number of changes in carbon allocation were observed. Shoot to root ratios increased with Al concentration in the Al-sensitive 'Katepwa' and remained constant in the Al-tolerant PT741.In both 'Katepwa' and PT741, shoot carbon was increasingly deposited into starch and fructan pools with increasing Al concentration. However, fructan deposition was more marked in the Al-sensitive 'Katepwa', possibly reflecting a failure to export carbon to the roots. Differences between Al-tolerant and Al-sensitive germ plasm were also observed in some organic acid levels. Contrary to several previous reports, higher concentrations of organic acids were found in the roots of Al-sensitive 'Katepwa'. In shoots, higher concentrations of organic acid were found in the Al-tolerant PT741. These results suggest that allocation of carbon to specific pools is affected by the concentration of Al. However, synthesis of organic acids and subsequent chelation of intracellular Al does not appear to represent a tolerance strategy in wheat. Observed changes in metabolic levels more likely represent a broad array of toxic lesions, with the magnitude of changes being greater in the Al-sensitive 'Katepwa' than in the Al-tolerant PT741. Key words: stress, aluminum tolerance, aluminum sensitivity, fructans.

Differential tolerance of manganese among cultivars of Triticum aestivum

Thirty cultivars of Triticum aestivum differed in tolerance of manganese (Mn) as determined by relative root growth in solution culture. Based upon a root weight index (RWI = root weight in the presence of 500 μM Mn divided by control root weight), Mn tolerance ranged from 0.08 to 0.88. All Canadian Western Red Spring (CWRS) cultivars tested were Mn sensitive. Cultivars bred for high yield were more Mn tolerant, especially 'Norquay' (RWI = 0.88) which was the only cultivar with a RWI > 0.70. The cultivars 'Norquay' and 'Columbus' were selected as standards for Mn tolerance and Mn sensitivity, respectively. 'Norquay' showed maximum root growth at 100 μM Mn, a concentration which was toxic to 'Columbus', and differential tolerance was maintained up to 1000 μM Mn in solution. Differences between 'Norquay' and 'Columbus', grown in excess Mn, were also observed in the accumulation of biomass with time. In contrast with previous studies, Mn tolerance was positively correlated with Al tolerance (R2 = 32.7, p = 0.001) in the cultivars tested.

The influence of elevated carbon dioxide concentrations on the partitioning of carbon in source leaves of Phaseolus vulgaris

Plants may alter their growth pattern in response to being grown in elevated CO2 concentrations. The nature of the change in carbon partitioning underlying those alterations was investigated in Phaseolus vulgaris cv. Gold Crop grown to the third trifoliate leaf stage in CO2 concentrations of 380, 800, and 1400 ppm. There was no effect of the CO2 concentration on plant height, leaf area, or dry weight, but the specific leaf weight increased significantly with the CO2, concentration, indicating a denser leaf structure. The starch content of the leaves also increased significantly as the CO2 level increased. A primary leaf was pulse labelled with 14CO2 and the depletion of label from that source leaf was monitored with a GM tube. The depletion of the count rate with time was described by a nonlinear curve fitting procedure that allowed the derivation of rate constants to describe the partitioning of carbon in a two-compartment model. Rates of carbon storage decreased in the light with increasing CO2 concentrations with no effect on the rates of export or remobilization. Both export and storage were reduced in the dark at all CO2 levels, with an increase in the residence time of carbon in the export pool. Reducing the CO2 concentration around the source leaf just after labelling did not change carbon partitioning compared to controls. Increasing the CO2 concentration around the source leaf just after labelling increased all carbon flux rates and reduced the residence times in the leaf pools.

The effects of oil spill chemicals on carbon translocation rates in Phaseolus vulgaris L

Phaseolus vulgaris L. cv. Black Valentine when sprayed with Corexit dispersants shows a rapid inhibition of photosynthesis. The plant retains the ability to translocate fixed carbon, and this involves mobilising previously fixed carbon in the sprayed leaf or the repartitioning of carbon from unsprayed regions of the plant towards the growing sink regions. The ability to maintain carbon translocation while photosynthesis is declining maximises the regrowth potential of the plant.

The effect of crude oil and oil spill chemicals on nitrogen fixation in the cyanobacteria Nostoc sp

The effects of crude oil and three oil spill dispersants (Corexit 9600, 9550 and 7664) on nitrogenase activity in the cyanobacteria Nostoc sp. were examined. The addition of oil to Nostoc sp. cultures resulted in a catastrophic decline in nitrogenase activity with activity ceasing 7 h after treatment. The addition of a dispersant with the oil did not ameliorate this effect. Cultures exposed to high concentrations of dispersants showed lower rates on nitrogenase activity than untreated cultures. However, it is unlikely that dispersant concentrations of this magnitude would occur in the field. At the lowest concentration tested, which approximates the manufacturer's recommended application rate, the effects of the dispersant appear to be negligible.

The influence of plant temperature on photosynthesis and translocation rates in bean and soybean

Phaseolus vulgaris cv. Black Valentine and Glycine max cv. Maple Arrow and cv. Evans were grown at 20 °C. They were pruned to a simple source – sink system and placed in a steady-state 14C-labeling system, where their photosynthesis and translocation rates were determined at the growth temperature. The temperature of each plant was then raised or lowered and the rates were measured again. All three varieties showed net photosynthetic optima near the growth temperature. Translocation rates increased sigmoidally from 5 to 35 °C in Phaseolus, giving a decreasing Q10 value, but exponentially from 5 to 40 °C in Glycine, giving a Q10 of about 2.0. Rates were suboptimal at the highest temperatures used. Plants grown at 30 °C and exposed to higher or lower temperatures responded in parallel to the 20 °C grown plants. When grown at 12.5 °C and exposed to higher temperatures, the plants responded in parallel to the 20 °C grown ones, but at lower temperatures translocation was higher than predicted for cv. Maple Arrow.

The effects of oil spill chemicals on transpiration, CO2 exchange, and cuticular structure in Salix interior

The effects of three oil spill chemicals (Corexit 9600, 9550, and 7664) on cuticular structure and function in the sandbar willow Salix interior were assessed from direct observations of the leaf surface, using scanning electron microscopy, and from measurements of water loss through transpiration. Rates of CO2 exchange in the light and dark were also measured. Although the Corexits coated the leaf surfaces, wax plates (crystals) associated with the cuticle were not visibly altered. The dispersants did not increase rates of evaporative water loss. Rates of net CO2 assimilation in the light, however, were reduced by 54, 63, and 94% 1 h after contact with Corexit 7664, 9550, and 9600, respectively. Measurements of surface contact angles and observations on the movement of dye–dispersant mixtures indicated that the rapid inhibition of CO2 assimilation resulted from the spontaneous infiltration of stomata by the dispersants and direct action on the internal tissues of the leaf. Rates of dark respiration were initially unaffected but decreased after 1 day. Further reductions in rates of CO2 exchange were observed over the first 4 days (associated with extensive leaf chlorosis and necrosis); then the rates increased following new tissue growth. Although the dispersants are potent contact poisons, damage to the protective cuticle in Salix interior does not appear to be a major contributing factor to their toxicity.

The responses of photosynthesis and translocation rates to changes in the ζ ratio of light

The influence of wide spectrum illumination conditions, with red and far-red light mixed to simulate sun and shade conditions, upon rates of photosynthesis and translocation was observed. A steady-state 14CO2 labeling apparatus was used to measure the two processes simultaneously during a light quality change. Sun conditions supported lower rates of photosynthesis and translocation to illuminated sink leaves than shade conditions, but the rate of translocation was lower than expected on the basis of the decline in photosynthesis. Translocation rates to darkened sinks remained constant as the photosynthetic rates were altered by changing light quality. Sink leaflet growth rates were lower in sun than shade light. We conclude that this decline in growth rate, which is also a decline in sink strength, results in light quality exerting a smaller effect on translocation than on photosynthesis.

Alterations in source-sink patterns by modifications of source strength

Bean plants, trimmed to a simplified "double source, double sink" translocation system (the paired primary leaves serving as the double source and the paired lateral leaflets of the immature first trifoliate leaf as the double sink) were used to study the magnitude and short-term time course of change in the allocation ratio (partition ratio) of assimilates translocated from the labeled primary leaf to its respective "near" and "far leaflet" sinks in response to an increase or decrease in the source strength of the opposite primary leaf (the "control" leaf). If the rates of net photosynthesis in the two primary leaves were similar, assimilates from the labeled source leaf partitioned to the leaflet sinks in the ratio of 5:1 or higher, the dominant sink being the leaflet "nearer" to the labeled source leaf. If the rate of net photosynthesis in the control leaf was increased substantially above that of the labeled source leaf, the rate of translocation from the labeled source to either the near leaflet sink or far leaflet sink remained unaffected, despite, presumably, a higher translocation rate from the control leaf, and hence a higher phloem pressure gradient (or increased cross-sectional area) in the transport pathway from the control leaf to the leaflet sinks. If the control leaf was excised, thus reducing the source leaf area by about a half, the translocation rate from the remaining source leaf rapidly doubled, the partition ratio becoming equal to unity. If the control leaf was darkened, the partition ratio adjusted to an intermediate value. Although export rates from the labeled source leaf were increased either by excising or darkening the control leaf, the rate of net photosynthesis in the labeled leaf remained constant.

The influence of simulated canopy light on the growth of six acrocarpous moss species

Six moss species were grown in two growth chambers with similar environmental conditions except for their ç ratios (E660:E730). One chamber simulated a sunlit situation the other a subcanopy shade situation. Different growth responses were observed for several species in the two chambers, which were often in the opposite direction to observations made on vascular plants. The ç ratio may be an important factor in regulating the distribution of mosses in the natural environment.

Rapid influences of water stress on photosynthesis and translocation in Phaseolus vulgaris

A steady-state 14C labelling system is used to simultaneously measure rates of photosynthesis and translocation before and after the onset of an osmotic shock to the base of rooted or rootless Phaseolus vulgaris plants. In all experiments, the photosynthetic rate declines soon after the onset of a shock owing to rapid stomatal closure. The translocation rate, following a brief transient change, remains almost constant for several hours, indicating less sensitivity to osmotic shock than is shown by the photosynthetic rate. The transient changes in translocation rate are due to transient changes in the leaf relative water content. The direction of the transient depends on the nature of the osmoticum and the presence or absence of roots.

Effect of light and ontogenetic stage on sink strength in bean leaves

Light (about 3,000 foot-candles) neither increased nor decreased the sink strength of young, rapidly expanding leaves of Phaseolus vulgaris L. cv. Black Valentine, as measured by the comparative rates of import of (14)C-labeled photosynthates by sink leaves in the light versus dark in short term experiments. Although irradiated sink leaves accumulated more (14)C activity, the difference was fully accounted for by photosynthetic reabsorption of respiratory CO(2) derived from substrates translocated to the sink leaves.Maximum sink strength was attained when the sink leaf reached 7 to 8 cm(2) in area (9 to 10% of its fully expanded size). Thereafter sink strength declined rapidly and asymptotically to a near zero value at about 45% final area. During this period, however, the rapid decline in translocation was offset by a rapid rise in the photosynthetic rate of the sink leaf, maintaining a near constant relative rate of dry weight increase until the sink leaf had expanded to about 17% of its final area. Although the increasing photosynthetic capacity was associated with a decreasing import capacity, suggesting that the rate of translocation to the sink leaf was controlled by the developing capacity of the sink leaf for photosynthesis, it was not possible to vary the total (true) translocation rate to the sink leaf by varying the photosynthetic rate of the sink leaf in short term light-dark experiments. Despite a high ratio of source to sink in these experiments, no evidence accrued that translocation into young bean leaves was ever sink-limited.

Translocation of 14C-labeled assimilates in petioles and phloem loops of Heracleum lanatum

The translocation of 14C-assimilates in intact petioles of Heracleum lanatum Michx. was compared with that in wounded petioles with isolated phloem loops. Wounding the petiole in isolating the loops interfered with normal translocation by stopping movement of 14C-assimilates in the isolated loop but not in the rest of the petiole. The isolated loop, however, took up and transported sucrose-6-6′ T, both acropetally and basipetally, from a solution in which a 1-cm length was bathed. A range of buffer and other solutions was used to bathe the petiole and loops during and after wounding, but translocation of 14C-assimilates in the loops could not be restored. The inability of isolated loops to translocate 14C-assimilates did not appear to be caused by desiccation, slime-plugging, or callosing. The mechanisms involved in transport of externally applied sucrose in isolated phloem loops appear to be different from those involved in the translocation of assimilates. Incision seemed to affect the latter in a region at some distance from the site of wounding.

A study of the carbohydrates in the cell walls of some species of the Entomophthorales

The cell walls of some members of the Entomophthorales were isolated and analyzed for their carbohydrate composition. Genera were found to differ qualitatively, while the species of Entomophthora differed only quantitatively. Among the differences, the glucose–mannose ratio emerged as the most useful taxonomic criterion. Differences in cell wall carbohydrate composition paralleled differences in lipid composition previously reported in species of Entomophthora. Because of the absence of chitosan, the Entomophthorales should not be grouped with the Mucorales on the basis of their cell wall carbohydrates, but should form a new group of chitin–glucan fungi.