title: Carbohydrate storage and remobilisation: The mechanisms involved in woody stem tissue of apple trees

authors: McQueen, Joanna C.

abstract: This thesis investigated the storage and remobilisation of carbohydrate reserves in perennial woody stem tissue, using one-year-old apple stems. In this study, the theories developed in herbaceous annual species were applied to woody perennial plants. Perennial plants are more complicated to study as they need reserves over a longer temporal scale and the woody tissue makes experimental manipulation difficult. In addition, apple is a multiple carbohydrate transporter and sorbitol (a sugar alcohol) is a major translocation product. These complications were overcome in this thesis, allowing hypotheses, developed from knowledge of carbohydrate movement in herbaceous plants, to be tested. The hypotheses were tested by manipulating sink conditions, 14C and 11C tracer experiments, use of inhibitors and enzyme extractions. 
The findings allowed models of carbohydrate storage and remobilisation in stem tissue of apple to be made. The sieve elements of apple are leaky pipes and assimilates are lost through passive leakage or active unloading during their journey from source to terminal sink. During remobilisation of carbohydrate in spring, retrieval of this leaked assimilate back into the phloem stream is up-regulated. This retrieval is likely to be directly into the sieve elements and involves carriers similar to those found in herbaceous annuals. Buffering also occurs along the stem length to prevent interruption to flow from short-term changes in photoassimilate supply. Buffering, leakage and retrieval probably occur into the apoplast. Starch is initially remobilised from storage cells closest to the phloem region in the spring. Sorbitol in the stem probably cannot be metabolised, which allows sorbitol to exist in high concentrations in the stem where it could act as a temporary (days to weeks) storage pool and could play a buffering role, maintaining a constant flow of sorbitol to sink tissue. 
During storage in autumn, when terminal sink tissue is either removed or saturated, assimilates continue to be lost from the leaky sieve tubes. However, retrieval is down-regulated so high concentrations of sugars build up in the stem apoplast. This results in storage of carbohydrate as starch, initially into the cells surrounding the phloem. Storage in the stem is given the lowest priority in terms of accumulating available carbohydrate and only occurs when there is an excess of photoassimilate, such as when higher priority sinks like fruit are removed or saturated. Eventually starch storage will saturate (at a concentration of 50mg g-1 in trees growing in the Hawkes Bay). Saturation of storage is likely to reduce concentration gradients between sieve elements and the apoplast, leading to a build up of sugars in the sieve elements and reduced assimilate flow. This is likely to result in a reduction or stoppage of photosynthesis, followed by leaf senescence. 
The results of this thesis show that most of the processes of carbohydrate storage and remobilisation in herbaceous plants also occur in woody perennial plants and this has increased our knowledge of basic plant processes. In order to manipulate source-sink relationships in plants to increase crop yields, we need to understand the physiological processes involving the movement of carbohydrates. The retrieval and release of sugars along the transport phloem is important, as there is a balance between supplying terminal sinks with photosynthate and retention of photosynthate along the pathway. In addition, physiological studies into apple trees are sparse. It was important to go to the next stage of carbohydrate studies in apple trees, beyond orchard management, and understand the physiological processes involved in carbohydrate movement and remobilisation. Apple is a high yielding crop and knowledge of the carbohydrate processes in this plant could help to increase yields in other commercially important tree species.

text: Carbohydrate storage and remobilisation: The mechanisms involved in woody stem tissue of apple trees This thesis investigated the storage and remobilisation of carbohydrate reserves in perennial woody stem tissue, using one-year-old apple stems. In this study, the theories developed in herbaceous annual species were applied to woody perennial plants. Perennial plants are more complicated to study as they need reserves over a longer temporal scale and the woody tissue makes experimental manipulation difficult. In addition, apple is a multiple carbohydrate transporter and sorbitol (a sugar alcohol) is a major translocation product. These complications were overcome in this thesis, allowing hypotheses, developed from knowledge of carbohydrate movement in herbaceous plants, to be tested. The hypotheses were tested by manipulating sink conditions, 14C and 11C tracer experiments, use of inhibitors and enzyme extractions. 
The findings allowed models of carbohydrate storage and remobilisation in stem tissue of apple to be made. The sieve elements of apple are leaky pipes and assimilates are lost through passive leakage or active unloading during their journey from source to terminal sink. During remobilisation of carbohydrate in spring, retrieval of this leaked assimilate back into the phloem stream is up-regulated. This retrieval is likely to be directly into the sieve elements and involves carriers similar to those found in herbaceous annuals. Buffering also occurs along the stem length to prevent interruption to flow from short-term changes in photoassimilate supply. Buffering, leakage and retrieval probably occur into the apoplast. Starch is initially remobilised from storage cells closest to the phloem region in the spring. Sorbitol in the stem probably cannot be metabolised, which allows sorbitol to exist in high concentrations in the stem where it could act as a temporary (days to weeks) storage pool and could play a buffering role, maintaining a constant flow of sorbitol to sink tissue. 
During storage in autumn, when terminal sink tissue is either removed or saturated, assimilates continue to be lost from the leaky sieve tubes. However, retrieval is down-regulated so high concentrations of sugars build up in the stem apoplast. This results in storage of carbohydrate as starch, initially into the cells surrounding the phloem. Storage in the stem is given the lowest priority in terms of accumulating available carbohydrate and only occurs when there is an excess of photoassimilate, such as when higher priority sinks like fruit are removed or saturated. Eventually starch storage will saturate (at a concentration of 50mg g-1 in trees growing in the Hawkes Bay). Saturation of storage is likely to reduce concentration gradients between sieve elements and the apoplast, leading to a build up of sugars in the sieve elements and reduced assimilate flow. This is likely to result in a reduction or stoppage of photosynthesis, followed by leaf senescence. 
The results of this thesis show that most of the processes of carbohydrate storage and remobilisation in herbaceous plants also occur in woody perennial plants and this has increased our knowledge of basic plant processes. In order to manipulate source-sink relationships in plants to increase crop yields, we need to understand the physiological processes involving the movement of carbohydrates. The retrieval and release of sugars along the transport phloem is important, as there is a balance between supplying terminal sinks with photosynthate and retention of photosynthate along the pathway. In addition, physiological studies into apple trees are sparse. It was important to go to the next stage of carbohydrate studies in apple trees, beyond orchard management, and understand the physiological processes involved in carbohydrate movement and remobilisation. Apple is a high yielding crop and knowledge of the carbohydrate processes in this plant could help to increase yields in other commercially important tree species.

year: 2003

title: The Window-motif in Rilke's poetry

authors: Mills, Philip John

abstract: In this dissertation my object is twofold: to examine where and how Rilke used the motif of the window, and also to discover the meaning this had for him. To this end, I propose to briefly review the chronology of the major window- poems and the broad background to them in Chapter I. This will in itself reveal just how significant the motif is and where it occurs. The following chapters will be given over to detailed analyses of those poems most significant to the second object of my investigation. Therefore, Chapter II will deal entirely with the earliest of these, "Die Fensterrose", Chapter III with the cycle Les Fenêtres, and Chapter IV with that poem which 'sums up' what Rilke wrote on the window, "LÄNGST, von uns Wohnenden fort,…”. Finally, a conclusion will not only summarize my findings, but also indicate the development to the final vision of the window .es. Definition of the “Intentional Community"

text: The Window-motif in Rilke's poetry In this dissertation my object is twofold: to examine where and how Rilke used the motif of the window, and also to discover the meaning this had for him. To this end, I propose to briefly review the chronology of the major window- poems and the broad background to them in Chapter I. This will in itself reveal just how significant the motif is and where it occurs. The following chapters will be given over to detailed analyses of those poems most significant to the second object of my investigation. Therefore, Chapter II will deal entirely with the earliest of these, "Die Fensterrose", Chapter III with the cycle Les Fenêtres, and Chapter IV with that poem which 'sums up' what Rilke wrote on the window, "LÄNGST, von uns Wohnenden fort,…”. Finally, a conclusion will not only summarize my findings, but also indicate the development to the final vision of the window .es. Definition of the “Intentional Community"

year: 1972

title: Life history of fluvial and lacustrine land-locked koaro (Galaxias brevipinnis) Günther (Pisces: galaxiidae) in the Tarawera lakes

authors: Young, Kim D.

abstract: Biological diversity in New Zealand has been seriously degraded as a result of human induced disturbances which include the introduction of many exotic species. Freshwater ecosystems have not escaped damage, with the introduction of primarily sports fish suspected to be a significant contributing factor in diminished native biological freshwater values. This is reflected by range and population reductions of several native fish species. 

One of these species is koaro (Galaxias brevipinnis), for which abundance in land-locked populations in the central North Island lakes has significantly declined. Koaro were once abundant in these lakes, and pre-European harvest in both its juvenile (whitebait) and adult (kokopu) form, comprised an important food resource for inland Maori. Since the introduction of recreational trout species to these lakes in the late 1880s, followed by the introduction of common smelt (Retropinna retropinna) in the early 1900s, the abundance of koaro has dramatically declined to the extent that, in these lakes, the species is now considered rare. 

To date, the interactions between recreational trout species, common smelt, and koaro populations have not been established, and the life-history of land-locked koaro is not fully understood. In particular, the extent of movement between lake and stream habitats remains unclear. However, a collaborative project between the indigenous people of the Rotorua Lakes (Te Arawa) and the Department of Conservation to restore a koaro population in one Rotorua lake, has driven a need to gain a better understanding of the biology and ecology of land-locked koaro. This includes identifying threats to important life-history stages and understanding the role of tributary streams.

During July 1999 to February 2001, lacustrine and fluvial koaro were studied in Lake Tarawera and Lake Okareka and their tributary streams. Both lakes are part of the Tarawera lakes group, a subgroup of the Rotorua lakes situated in the central North Island. Fyke netting was used to sample lacustrine koaro on a monthly basis from January 2000 to February 2001, and seasonal two-pass reduction electric fishing at five sites in the tributary streams took place in April, July and November 2000 and February 2001. All fish larger than 70 mm total length were tagged with a passive implant transponder. Spawning season and location, together with size and growth of lake and stream fish were determined. Movement of lake fish within the littoral zone was also investigated. 

The study found that lake and stream koaro may belong to two sub-populations indicated by differences in size, growth rate, spawning time and locality, and return of lake and stream koaro to natal habitats. The life-history of stream koaro has remained similar to that of its diadromous counterparts. Stream fish were found to spawn and hatch in stream environs, rear as larvae in the lake environs, and return to tributary streams as juvenile fish. Lake fish by contrast, most likely spawn in the lake itself, and results suggest that no juvenile migration of lake spawned fish to tributary streams occurs. Consequently, it was concluded that tributary streams may play little role in the life-history of lacustrine koaro.

Abundance of lacustrine koaro in both Lake Tarawera and Lake Okareka was low in comparison to lakes where trout species or common smelt are absent, and abundance of post-whitebait koaro (greater than 45 mm total length coloured and patterned) in both tributary streams studied was also low where rainbow trout (Oncorhynchus mykiss) were proportionally present in greater abundance. Important life-history stages were found to be subject to competition and predation by a combination of rainbow trout and common smelt in both lakes and streams.

Given the above, restoration programmes for land-locked koaro will need to be undertaken at the population level to enhance the survival of larval and juvenile life-history stages. This will need to occur at an ecosystem scale, and include the management of the combined effects of trout and common smelt in both lake and respective tributary stream environs.

text: Life history of fluvial and lacustrine land-locked koaro (Galaxias brevipinnis) Günther (Pisces: galaxiidae) in the Tarawera lakes Biological diversity in New Zealand has been seriously degraded as a result of human induced disturbances which include the introduction of many exotic species. Freshwater ecosystems have not escaped damage, with the introduction of primarily sports fish suspected to be a significant contributing factor in diminished native biological freshwater values. This is reflected by range and population reductions of several native fish species. 

One of these species is koaro (Galaxias brevipinnis), for which abundance in land-locked populations in the central North Island lakes has significantly declined. Koaro were once abundant in these lakes, and pre-European harvest in both its juvenile (whitebait) and adult (kokopu) form, comprised an important food resource for inland Maori. Since the introduction of recreational trout species to these lakes in the late 1880s, followed by the introduction of common smelt (Retropinna retropinna) in the early 1900s, the abundance of koaro has dramatically declined to the extent that, in these lakes, the species is now considered rare. 

To date, the interactions between recreational trout species, common smelt, and koaro populations have not been established, and the life-history of land-locked koaro is not fully understood. In particular, the extent of movement between lake and stream habitats remains unclear. However, a collaborative project between the indigenous people of the Rotorua Lakes (Te Arawa) and the Department of Conservation to restore a koaro population in one Rotorua lake, has driven a need to gain a better understanding of the biology and ecology of land-locked koaro. This includes identifying threats to important life-history stages and understanding the role of tributary streams.

During July 1999 to February 2001, lacustrine and fluvial koaro were studied in Lake Tarawera and Lake Okareka and their tributary streams. Both lakes are part of the Tarawera lakes group, a subgroup of the Rotorua lakes situated in the central North Island. Fyke netting was used to sample lacustrine koaro on a monthly basis from January 2000 to February 2001, and seasonal two-pass reduction electric fishing at five sites in the tributary streams took place in April, July and November 2000 and February 2001. All fish larger than 70 mm total length were tagged with a passive implant transponder. Spawning season and location, together with size and growth of lake and stream fish were determined. Movement of lake fish within the littoral zone was also investigated. 

The study found that lake and stream koaro may belong to two sub-populations indicated by differences in size, growth rate, spawning time and locality, and return of lake and stream koaro to natal habitats. The life-history of stream koaro has remained similar to that of its diadromous counterparts. Stream fish were found to spawn and hatch in stream environs, rear as larvae in the lake environs, and return to tributary streams as juvenile fish. Lake fish by contrast, most likely spawn in the lake itself, and results suggest that no juvenile migration of lake spawned fish to tributary streams occurs. Consequently, it was concluded that tributary streams may play little role in the life-history of lacustrine koaro.

Abundance of lacustrine koaro in both Lake Tarawera and Lake Okareka was low in comparison to lakes where trout species or common smelt are absent, and abundance of post-whitebait koaro (greater than 45 mm total length coloured and patterned) in both tributary streams studied was also low where rainbow trout (Oncorhynchus mykiss) were proportionally present in greater abundance. Important life-history stages were found to be subject to competition and predation by a combination of rainbow trout and common smelt in both lakes and streams.

Given the above, restoration programmes for land-locked koaro will need to be undertaken at the population level to enhance the survival of larval and juvenile life-history stages. This will need to occur at an ecosystem scale, and include the management of the combined effects of trout and common smelt in both lake and respective tributary stream environs.

year: 2002