Effect of nitrogen supply on leaf appearance, leaf growth, leaf nitrogen economy and photosynthetic capacity in maize (Zea mays L.)

Leaf area growth and nitrogen concentration per unit leaf area, N-a (g m(-2) N) are two options plants can use to adapt to nitrogen limitation. Previous work indicated that potato (Solanum tuberosum L.) adapts the size of leaves to maintain Na and photosynthetic capacity per unit leaf area. This paper reports on the effect of N limitation on leaf area production and photosynthetic capacity in maize, a C4 cereal. Maize was grown in two experiments in pots in glasshouses with three (0.84-6.0 g N pot(-1)) and five rates (0.5-6.0 g pot(-1)) of N. Leaf tip and ligule appearance were monitored and final individual leaf area was determined. Changes with leaf age in leaf area, leaf N content and light-saturated photosynthetic capacity, P a,, were measured on two leaves per plant in each experiment. The final area of the largest leaf and total plant leaf area differed by 16 and 29% from the lowest to highest N supply, but leaf appearance rate and the duration of leaf expansion were unaffected. The N concentration of expanding leaves (N-a or %N in dry matter) differed by at least a factor 2 from the lowest to highest N supply. A hyperbolic function described the relation between P-max and N-a. The results confirm the 'maize strategy': leaf N content, photosynthetic capacity, and ultimately radiation use efficiency is more sensitive to nitrogen limitation than are leaf area expansion and light interception. The generality of the findings is discussed and it is suggested that at canopy level species showing the 'potato strategy' can be recognized from little effect of nitrogen supply on radiation use efficiency, while the reverse is true for species showing the 'maize strategy' for adaptation to N limitation. (c) 2004 Elsevier B.V. All rights reserved.

Attitude change and the public-private attitude distinction

In this paper, we highlight the importance of the distinction between public and private attitudes in research on attitude change. First, we clarify the definitions of public and private attitudes by locating the researcher as a potential source of influence. In a test of this definition, we compare participant reports of potentially embarrassing behaviour and the study's importance between participants responding when a researcher has potential access to their reports (public condition), and participants whose reports the researcher has no potential access to (private condition). Participants high in public self-focus or low in defensive self-presentation reported the study to be more important in the public condition than the private condition. Further, participants in the public condition reported less frequency of engaging in embarrassing behaviours than those in the private condition, an effect not moderated by individual differences. We conclude that the public-private distinction is an essential element in attitude change theory.

Virtual reality exposure therapy: 150-degree screen to desktop PC

Virtual reality exposure therapy (VRET) developed using immersive or semi-immersive virtual environments present a usability problem for practitioners. To meet practitioner requirements for lower cost and portability VRET programs must often be ported onto desktop environments such as the personal computer (PC). However, success of VRET has been shown to be linked to presence, and the environment's ability to evoke the same reactions and emotions as a real experience. It is generally accepted that high-end virtual environments ( VEs) are more immersive than desktop PCs, but level of immersion does not always predict level of presence. This paper reports on the impact on presence of porting a therapeutic VR application for Schizophrenia from the initial research environment of a semi-immersive curved screen to PC. Presence in these two environments is measured both introspectively and across a number of causal factors thought to underlie the experience of presence. Results show that the VR exposure program successfully made users feel they were present in both platforms. While the desktop PC achieved higher scores on presence across causal factors participants reported they felt more present in the curved screen environment. While comparison of the two groups was statistically significant for the PQ but not for the IPQ, subjective reports of experiences in the environments should be considered in future research as the success of VRET relies heavily on the emotional response of patients to the therapeutic program.

Enhancing Life in the Hyper-surveillance Mini-world of a Space Station: The Role of Situation Awareness, Communication, and Reality TV in the Life of Astronauts

This is the third article of a series entitled Astronauts as Audiences. In this article, we investigate the roles that situation awareness (SA), communications, and reality TV (including media communications) might have on the lives of astronauts in remote space communities. We examined primary data about astronauts’ living and working environments, applicable theories of SA, communications, and reality TV (including media communications). We then surmised that the collective application of these roles might be a means of enhancing the lives of astronauts in remote space communities.

An examination of the effects of print media exposure and contact on subjective social reality and acculturation attitudes

This study draws upon cultivation theory, acculturation theory, and works on intergroup relations to examine the effects of print media exposure and contact on subjective social reality and acculturation attitudes of Chinese immigrants in Australia. Data was gathered via a survey administered to 265 respondents with Chinese origin. Results indicate that exposure to mainstream newspapers is only positively related to one indicator of subjective reality, namely, outgroup perception whereas exposure to ethnic newspapers was not significantly related to any of the indicators of subjective reality. Acculturation attitudes, on the other hand, are more closely related to group perception and contact but not closely associated with exposure to print media. These findings have again challenged the direct effect assumption of cultivation theory, paved the ground for combining mediated communication variables with interpersonal communication variables in acculturation research and suggested policy implications for interethnic coexistence. (c) 2005 Elsevier Ltd. All rights reserved.