title: Water relations and carbon dioxide exchange of epiphytic lichens in the Namib fog desert

authors: Lange, Otto L.

subjects: dew

abstract: Although there is only negligible rainfall, frequent nocturnal fog, dew and high air humidity support a luxurious lichen vegetation in the coastal zone of the central NamibDesert (Namibia). In earlier publications, we have studied ecophysiological performance of a series of epilithic and terrestrial lichens. Here, we have extended this work to three epiphytic species (Heterodermia namaquana, Ramalina lacera, and Xanthoria turbinata) that inhabit the sparse perennial shrubs growing in this area. Our intention, monitoring lichen CO₂ exchange, their waterrelations and microclimate conditions, was to determine the functional mechanisms that allow these epiphytes to exist under the special conditions of a fogdesert. Measurements were conducted mainly during the spring season.
The epiphyticlichens showed response patterns very similar to the epilithic and epigaeic species at the same site. Their metabolism was activated through moistening by dew and/or fog during the night and, in the very early morning, they exhibited the typical brief peak of net photosynthesis (NP) between sunrise and desiccation. The thalli were almost completely dry for the remainder of the day. Average duration of the positive NP during the morning peak was about 3 h. Dew condensation, alone, resulted in activation that provided 58–63% of integrated carbon income (ΣNP) as compared to fog (plus dew). In the late afternoon, there was a tendency for hydration to increase again, due to water vapour uptake at higher air humidity, and this allowed on some days a brief additional period of very low rates of photosynthesis shortly before sunset.
Light response of photosynthesis showed “sun-plant” characteristics with saturation around 1000 μmol m⁻² s⁻¹ photosynthetically active photon flux density (PPFD). Light compensation point (LCP) of CO2exchange after sunrise was highly dependent on actual water content (WC) for X. turbinata: at low hydration it was ca. 10 μmol m⁻² s⁻¹ PPFD whilst, at high WC, it was almost 80 μmol m⁻² s⁻¹ PPFD. In contrast, LCP of R. lacera was almost independent of WC. This phenomenon was probably due to differences in thallus structure.
Maximal attained NP and daily ΣNP both showed a saturation-type response to previous maximal nocturnal WC. Neither parameter was increased substantially when higher maximal thallus WCs were produced by experimental moistening in the night. All three species, despite their different morphologies, performed optimally at the highest nocturnal moistening achieved by natural fog and were not able to make use of higher hydration.
The three studied epiphytes were similar in their chlorophyll-related rates of NP. Due to lower chlorophyll content, dry weight and carbon-related NP of X. turbinata was only about one-third of that of the other two species. The average carbon income on days with fog and/or dew hydration during the spring season amounted to 2.4 and 2.1 mgC (gC)⁻¹ day⁻¹ (related to thallus carbon content) for H. namaquana and R. lacera, respectively. This primary production was of similar magnitude to those found for the terrestrial species at the same site.

text: Water relations and carbon dioxide exchange of epiphytic lichens in the Namib fog desert Although there is only negligible rainfall, frequent nocturnal fog, dew and high air humidity support a luxurious lichen vegetation in the coastal zone of the central NamibDesert (Namibia). In earlier publications, we have studied ecophysiological performance of a series of epilithic and terrestrial lichens. Here, we have extended this work to three epiphytic species (Heterodermia namaquana, Ramalina lacera, and Xanthoria turbinata) that inhabit the sparse perennial shrubs growing in this area. Our intention, monitoring lichen CO₂ exchange, their waterrelations and microclimate conditions, was to determine the functional mechanisms that allow these epiphytes to exist under the special conditions of a fogdesert. Measurements were conducted mainly during the spring season.
The epiphyticlichens showed response patterns very similar to the epilithic and epigaeic species at the same site. Their metabolism was activated through moistening by dew and/or fog during the night and, in the very early morning, they exhibited the typical brief peak of net photosynthesis (NP) between sunrise and desiccation. The thalli were almost completely dry for the remainder of the day. Average duration of the positive NP during the morning peak was about 3 h. Dew condensation, alone, resulted in activation that provided 58–63% of integrated carbon income (ΣNP) as compared to fog (plus dew). In the late afternoon, there was a tendency for hydration to increase again, due to water vapour uptake at higher air humidity, and this allowed on some days a brief additional period of very low rates of photosynthesis shortly before sunset.
Light response of photosynthesis showed “sun-plant” characteristics with saturation around 1000 μmol m⁻² s⁻¹ photosynthetically active photon flux density (PPFD). Light compensation point (LCP) of CO2exchange after sunrise was highly dependent on actual water content (WC) for X. turbinata: at low hydration it was ca. 10 μmol m⁻² s⁻¹ PPFD whilst, at high WC, it was almost 80 μmol m⁻² s⁻¹ PPFD. In contrast, LCP of R. lacera was almost independent of WC. This phenomenon was probably due to differences in thallus structure.
Maximal attained NP and daily ΣNP both showed a saturation-type response to previous maximal nocturnal WC. Neither parameter was increased substantially when higher maximal thallus WCs were produced by experimental moistening in the night. All three species, despite their different morphologies, performed optimally at the highest nocturnal moistening achieved by natural fog and were not able to make use of higher hydration.
The three studied epiphytes were similar in their chlorophyll-related rates of NP. Due to lower chlorophyll content, dry weight and carbon-related NP of X. turbinata was only about one-third of that of the other two species. The average carbon income on days with fog and/or dew hydration during the spring season amounted to 2.4 and 2.1 mgC (gC)⁻¹ day⁻¹ (related to thallus carbon content) for H. namaquana and R. lacera, respectively. This primary production was of similar magnitude to those found for the terrestrial species at the same site.

year: 2007

title: Influence of nitrogen on the primary and secondary metabolism and synthesis of flavonoids in Chrysanthemum morifolium Ramat

authors: Liu, Wei

subjects: Chrysanthemum moriforlium Ramat

abstract: The effects of nitrogen (N) supply on nitrogen metabolism in leaves of Chrysanthemum morifolium Ramat. were examined in five different stages throughout the growing season. The results suggested that flavonoids content was positively related to phenylalanine ammonia-lyase activity through the whole growing stage of the plant but with a decreasing correlation coefficient for increasing nitrogen supply. There was no correlation between flavonoids and 4-coumarate coenzyme A ligase. Soluble protein content was positively correlated with phenylalanine ammonia-lyase activity because there was little competition for the phenylalanine in the leaves under low nitrogen supply. Phenylalanine ammonia-lyase activity decreased gradually with increasing nitrogen supply because of the competition for the phenylalanine in protein synthesizes. The results suggest that nitrogen nutrition plays a key role in biosynthesis of enzymes in the leaves of C. morifolium.

text: Influence of nitrogen on the primary and secondary metabolism and synthesis of flavonoids in Chrysanthemum morifolium Ramat The effects of nitrogen (N) supply on nitrogen metabolism in leaves of Chrysanthemum morifolium Ramat. were examined in five different stages throughout the growing season. The results suggested that flavonoids content was positively related to phenylalanine ammonia-lyase activity through the whole growing stage of the plant but with a decreasing correlation coefficient for increasing nitrogen supply. There was no correlation between flavonoids and 4-coumarate coenzyme A ligase. Soluble protein content was positively correlated with phenylalanine ammonia-lyase activity because there was little competition for the phenylalanine in the leaves under low nitrogen supply. Phenylalanine ammonia-lyase activity decreased gradually with increasing nitrogen supply because of the competition for the phenylalanine in protein synthesizes. The results suggest that nitrogen nutrition plays a key role in biosynthesis of enzymes in the leaves of C. morifolium.

year: 2010

title: In what ways do the perceptions of connectedness of Māori students in Alternative Education secondary schools affect their self-efficacy within the learning environment?

authors: Lemon, Katrina Suezanne

subjects: Alternative Education

abstract: This study has sought to identify connectedness for Māori students within the alternative-education, learning environment and the effect this has had on their self-efficacy. Alternative education in New Zealand is described as a place where second chance learners have access to education (Alternative Education National Body New Zealand, 2016). Generally, students are referred to alternative education due to becoming habitual truants, while other students are deemed as behaviourally-challenging, and are consequently excluded from school (Education Review Office, 2010; Ministry of Education, 2016a). A Critical Theory approach was employed guided by Kaupapa Māori methodology. Data was collected using the qualitative methods of focus-group interviews and one-to-one semi-structured interviews. An open-coded approach was adopted to analyse the data from the interview transcripts where themes were selected, and a summary reflection was written. 

Three distant themes were identified during the data analysis phase: Tāhuhu Kōrero – Kura; Alternative Education – Kura; and Alternative Education Teaching and Learning Approaches.  Within these themes sub-themes were explored: perceptions and experiences of primary and secondary school; Māori in mainstream education; the referring schools involvement; misconceptions; connection to the alternative-education, learning environment; centre and teacher practices; connection with Māori; and pathways, mana, and self-efficacy. An important aspect of this study was to seek to understand these students’ prior educational experiences before gathering their narratives on the alternative-education, learning environment. This was a strength of the study as the student narratives on their entire educational journey provided a depth of understanding for the researcher, and went towards explaining their disconnection, how it happened, and gave context to their referral to alternative education. 

The student narratives expressed a strong sense of connection to their primary-school, learning environment, however, a complete disconnection to their secondary-school, learning environment. Students expressed feeling discriminated against for being Māori, that there was no empathy or understanding given to their lived realities despite wanting to succeed at school. They felt that their teachers did not make an effort to connect with them describing a power imbalance between the teachers and themselves. The students felt that expectations were low, and that teachers could not be bothered to help them with their work. The student participants attributed this disconnection to the reason for their truancy and behavioural issues. The student narratives on the alternative-education, learning environment described an environment that was: whānau; where teachers worked at a connection and understood their learners; challenging them academically; where the teachers were highly committed to their students; where trust and respect was built; and where one size did not fit all - flexibility was exercised. Students felt that the alternative-education, learning environment provided them with career ambition, and academic confidence resulting in self-efficacy. 

This study provides student voice from a group that was overlooked within the Te Kotahitanga research project (Bishop, Berryman, Tiakiwai, & Richardson, 2003). To hear the voice of alternative education students is important in seeking to improve educational success and enjoyment for Māori priority learners. If we get to know and understand what works for these priority learners, we can then work towards making a difference for them within mainstream education. This study aims to identify the importance of connectedness for Māori students and how connectedness will positively affect Māori learners and their self-efficacy. 


Kia mau ki tō Māoritanga.
Hold fast to your Māori culture.

text: In what ways do the perceptions of connectedness of Māori students in Alternative Education secondary schools affect their self-efficacy within the learning environment? This study has sought to identify connectedness for Māori students within the alternative-education, learning environment and the effect this has had on their self-efficacy. Alternative education in New Zealand is described as a place where second chance learners have access to education (Alternative Education National Body New Zealand, 2016). Generally, students are referred to alternative education due to becoming habitual truants, while other students are deemed as behaviourally-challenging, and are consequently excluded from school (Education Review Office, 2010; Ministry of Education, 2016a). A Critical Theory approach was employed guided by Kaupapa Māori methodology. Data was collected using the qualitative methods of focus-group interviews and one-to-one semi-structured interviews. An open-coded approach was adopted to analyse the data from the interview transcripts where themes were selected, and a summary reflection was written. 

Three distant themes were identified during the data analysis phase: Tāhuhu Kōrero – Kura; Alternative Education – Kura; and Alternative Education Teaching and Learning Approaches.  Within these themes sub-themes were explored: perceptions and experiences of primary and secondary school; Māori in mainstream education; the referring schools involvement; misconceptions; connection to the alternative-education, learning environment; centre and teacher practices; connection with Māori; and pathways, mana, and self-efficacy. An important aspect of this study was to seek to understand these students’ prior educational experiences before gathering their narratives on the alternative-education, learning environment. This was a strength of the study as the student narratives on their entire educational journey provided a depth of understanding for the researcher, and went towards explaining their disconnection, how it happened, and gave context to their referral to alternative education. 

The student narratives expressed a strong sense of connection to their primary-school, learning environment, however, a complete disconnection to their secondary-school, learning environment. Students expressed feeling discriminated against for being Māori, that there was no empathy or understanding given to their lived realities despite wanting to succeed at school. They felt that their teachers did not make an effort to connect with them describing a power imbalance between the teachers and themselves. The students felt that expectations were low, and that teachers could not be bothered to help them with their work. The student participants attributed this disconnection to the reason for their truancy and behavioural issues. The student narratives on the alternative-education, learning environment described an environment that was: whānau; where teachers worked at a connection and understood their learners; challenging them academically; where the teachers were highly committed to their students; where trust and respect was built; and where one size did not fit all - flexibility was exercised. Students felt that the alternative-education, learning environment provided them with career ambition, and academic confidence resulting in self-efficacy. 

This study provides student voice from a group that was overlooked within the Te Kotahitanga research project (Bishop, Berryman, Tiakiwai, & Richardson, 2003). To hear the voice of alternative education students is important in seeking to improve educational success and enjoyment for Māori priority learners. If we get to know and understand what works for these priority learners, we can then work towards making a difference for them within mainstream education. This study aims to identify the importance of connectedness for Māori students and how connectedness will positively affect Māori learners and their self-efficacy. 


Kia mau ki tō Māoritanga.
Hold fast to your Māori culture.

year: 2017