Bibliography: leaves 229-250. / xxi, 250 leaves : ill. (chiefly col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / The aims of the study were to develop a reliable method for screening for Zn efficiency as an alternative to the current field-based methods, and to determine the extent of genotypic variation in tolerance to Zn deficiency in barley. / Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Science, 1999

Bibliography: leaves 229-250. The aims of the study were to develop a reliable method for screening for Zn efficiency as an alternative to the current field-based methods, and to determine the extent of genotypic variation in tolerance to Zn deficiency in barley.

Transplanting is a common practice for many horticultural crops and some field crops. Recently, transplanted oilseed rape (Brassica napus L.) crops have been reported to be sensitive to zinc (Zn) deficiency. However, Zn nutrition in transplanted field crops has not been investigated in detail. The objectives of this present research were to investigate whether transplanting increases external Zn requirements of transplanted oilseed rape, and the mechanisms of root function, growth and Zn uptake after transplanting including rhizosphere modification capacity by plant roots. The second objective was to examine the relative effects of root pruning and transplanting on Zn responses of oilseed rape, and the third objective was to determine external and internal Zn requirements of transplanted oilseed rape for diagnosing and predicting Zn deficiency. An experiment on a low Zn sand (DTPA extractable Zn 0.14 mg kg-1) was set up to determine whether transplanted oilseed rape had a higher Zn requirement than that of direct-sown plants. Low Zn supply depressed shoot dry weight, however, root growth was relatively more strongly suppressed than shoots. Maximum root dry weight required much higher external Zn for transplanted plants compared to direct-sown plants, whilst shoot dry weight required a similarly low external Zn supply. In addition, transplanted plants were sensitive to zinc deficiency during the early post-transplanting growth, and the response weakened as the plants recovered from root injury or transplanting stress. However, the transplanted plants also experienced root pruning before transplanting and so in this experiment the higher Zn requirement could have been due to root pruning or transplanting or both. A further experiment was undertaken to determine the comparative external Zn requirements of direct-sown and transplanted plants in well-stirred chelate-buffered solution culture where a rhizosphere effect on plant availability of Zn forms is absent and the effects of poor root-soil contact on post-transplanting growth are minimized. In solution culture at the same level of Zn supplied, direct- sown plants produced higher shoot and root dry matter and greater root length than those of transplanted plants. However, since a higher external Zn requirement was found for transplanted plants in buffered solution culture than for direct- sown plants, it was concluded that the higher Zn requirement was not related to decreased rhizosphere modification, to greater demand for Zn or to poor root-solution contact, but rather to the time required for transplanted plants to recover from transplanting and root injury. The recovery of root function in solution culture was more rapid than that in soil culture and expressed as a higher Zn requirement for shoot as well as root growth. It suggested that the delay in root recovery in soil culture was due to slower absorption of Zn from the soil after transplanting than was the case in solution culture. Chelate-buffered nutrient solution culture and harvesting plants successively at 5 day intervals until 25 days after transplanting was used to examine the mechanisms of the recovery of root growth and function. In this experiment, the external Zn requirement of transplanted plants was investigated with unpruned or pruned root systems. Plants with unpruned root system and sufficient Zn supply exhibited faster recovery from transplanting than those with pruned root system plants. The results suggest that root pruning impaired Zn uptake by plant roots and slowed down the root and shoot growth after transplanting. Increased solution Zn partly alleviated the effects of root pruning and presumably this is a major reason why transplanted oilseed rape had a high external Zn requirement. However, root pruning also appeared to impair water uptake, and may have suppressed shoot growth through sequestering carbon for new root growth and through decreased phytohormone production by roots. Since rapid root recovery of transplanted plants is essential for successful of growth in the field, Zn application to the nursery bed was explored as a starter fertilizer to stimulate root growth after transplanting. The objective of this experiment was to determine whether increasing the seedbed Zn would stimulate new root growth of transplanted oilseed rape, and therefore would alleviate the need for increased external Zn for post-transplanting growth. Results showed that adequate Zn concentration in the seedbed promoted the post-transplanting growth by stimulating the new root growth especially increased root length, and also hastened the recovery of root systems. However, high Zn concentration at transplanting still had a more dominant effect in stimulating the new root growth of oilseed rape after transplanting. The final experiment was set up using rhizobags with three rates of Zn supply and unpruned or pruned root systems. The purpose of this study was to investigate the chemical change in the rhizosphere and non-rhizosphere or bulk soil and its relationship to the recovery of root function after transplanting, and also to identify and quantify the organic acids in soil extracts of direct-sown and transplanted plants. The rhizosphere soil pH was lower than that of non-rhizosphere soil, and the decrease of soil pH was suggested as the mechanism of the increase of Zn availability and mobility in the rhizosphere soil. Direct-sown plants were more efficient in utilizing Zn than those of transplanted plants especially compared to those of plants with pruned root system. Zinc deficient plants excreted higher concentration of organic acids particularly citric acid, suggesting this was a mechanism of Zn mobilization and Zn uptake by roots of oilseed rape. The main implications of the present study for the management of Zn nutrition of transplanted crops were: the need to increase the Zn application to crops in the nursery and at transplanting compared to direct-sown plants; the possibility that external requirements of other nutrients will be greater in transplanted crops also requires further consideration; and in cropping systems where transplanting is practised, greater attention should be given to the avoidance of root damage during the transplanting.

Bibliography: leaves 149-173.

Crop-available zinc is affected by P-Zn interactions in soils. Orthophosphate (OP) additions may decrease or have no effect, while pyrophosphate (PP) may increase or have no effect on Zn solubility. Mechanisms involved in the interactions are not well understood and need to be quantified on agricultural soils subjected to P fertilization. / Top and sub-samples from three Quebec agricultural soils were equilibrated with OP or PP solutions, then with Zn solutions, and finally with solutions containing neither P nor Zn. The first equilibration evaluated P sorption effects on soil cation exchange capacity (CEC), the second equilibration evaluated Zn sorption (Zn$ sb{ rm s}$) after P sorption, and the third Zn desorption (Zn$ sb{ rm D}$) as related to added P. Subsequently, Zn fractions were extracted sequentially with KNO$ sb3$ (Zn$ sb{ rm KNO3}$), NaOH (Zn$ sb{ rm NaOH}$) solutions and concentrated HNO$ sb3$ + H$ sb2$O$ sb2$ (Zn$ sb{ rm HNO3}$). Autoclaved soils were used for OP and PP comparisons, and non-autoclaved soils were used for OP determinations. / Autoclaving reduced dithionite-citrate extractable Fe and Al materials. In both autoclaved and non-autoclaved soils, one mmole sorbed P as PP or OP resulted in increases in CEC from 0.52-1.24 mmole (+). Comparison between OP and PP in the autoclaved soils indicated that the increased CEC per mmole sorbed was greater with sorbed OP than with PP, while at the same rate of P addition, the absolute increased CEC was more with sorbed PP than with OP due to greater P sorption as PP compared to OP. Both sorbed OP or PP in autoclaved soils and sorbed OP in non-autoclaved soils increased specific Zn sorption in association with oxide materials. The effect was more significant with PP than with OP, as indicated by the observations: (1) P sorption increased Zn sorption but reduced Zn desorption, (2) P sorption reduced KNO$ sb3$- but increased NaOH- and HNO$ sb3$-extractable Zn, and (3) P sorption increased the difference between Zn sorbed and Zn extracted with KNO$ sb3$. These effects were more significant in coarser than finer textured soils. Results suggested that Zn fertilizers should be separated from P fertilizers to avoid enhanced Zn sorption and reduced Zn desorption.

Bibliography: leaves 149-173. / xiv, 173 leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Science, 1994

Thesis (M.E.)--University of Canterbury, 2009. / Typescript (photocopy). "November 2009." Includes bibliographical references (leaves 73-78). Also available via the World Wide Web.

No description available.

Four experiments were performed to test the feasibility of using taxonomic composition and abundance of attached algae to identify treatments of zinc (Zn) alone and in combination with treatments of phosphate, snail grazing, and pH. In the experiment presented in chapter 2, three treatments of zinc (0.05, 0.5, 1.0 mg Zn•l⁻¹) and a control could be identified by different algal communities in outdoor, flow-through, stream mesocosms. Established communities were continuously exposed to Zn, and samples were collected on days 0, 2, 5, 10, 20, and 30 after treatment began. Experiments were conducted in spring, summer, and fall 1984. Control stream mesocosms could be identified by diatoms in all seasons. The 0.05 mg Zn•l⁻¹ treatment could be identified by certain diatom taxa being more abundant than in the control in all seasons and by a filamentous green·alga in summer and fall. The 0.5 mg Zn•l⁻¹ treatment could be identified a filamentous green alga in fall. The 1.0 mg Zn•l⁻¹ treatment could be identified by unicellular green-algae in all seasons and by a filamentous blue-green alga in summer. A similarity index (SIMI) indicated that Zn stressed samples generally became less similar to control samples as Zn concentration increased from 0.05 to 1.0 mg Zn•l⁻¹. Total biovolume·density of all taxa responded more slowly than did individual taxa in spring and failed to distinguish between Zn treatments in summer and fall. Zn bound to periphyton (microbial community on solid substrates) was more reliable than total Zn in water for identifying Zn treatments. Zn treatments as low as 0.05 mg Zn•l⁻¹ changed algal species composition. This conflicts with the criterion (0.047 mg Zn•l⁻¹) of the U. S. Environmental Protection Agency for the 24-hour average of total recoverable Zn. ln the experiment presented in chapter 3, individual and combined effects of phosphate (P) and zinc (Zn) on the abundance of dominant algae and protozoa in a community were observed. Nutrient·diffusing artificial substrates were colonized in Douglas Lake, Michigan, and then placed in laboratory microcosms containing one of five Zn treatments (control, 0.1, 1.0, 3.0, and 10.0 mg Zn•l⁻¹). After one week of exposure in the laboratory the substrates were scraped and algal and ciliated protozoan abundances determined. Ten of thirteen algae and five of eight ciliated protozoa responded to experimental treatments. Some algae (diatoms and green algae) and ciliated protozoa were stimulated by high P, some stimulated by intermediate P, and some inhibited by high P. One alga and four protozoa responded positively to Zn. Two algae and three protozoa responded to a significant interaction between P and Zn so that abundances were from 3 to 19 times higher than the added effects of individual P and Zn treatments. Total algal abundance was increased by high P and total protozoan abundance was increased by intermediate P but at control levels for high P. The number of protozoan species was increased by P. Total algal abundance was increased by · combinations of Zn P and the number of protozoan species was decreased by Zn P. Altered abundance by combinations of Zn and P had not been demonstrated for a community of algae and protozoa previously. Although concentrations of Zn were initially above the level considered safe by the U.S. Environmental Protection Agency, many factors may prevent Zn stress. In the experiment presented in chapter 4, effects of 0.5 mg Zn•l⁻¹ and snail grazing (400 snails m⁻²) on density of dominant algal taxa were examined using established (12-day colonization) periphyton communities in flow-through stream mesocosms with four treatments (Zn, snails, Zn and snails, control) for 30 days. Grazing and Zn similarly reduced the abundance of 5 of 10 dominant taxa during the first 10 days of treatment. Temperature may play a very important role in determining the effect of snail grazing on attached algal communities. Cold temperatures (< 15 C) may have inhibited snail grazing to the extent that abundance of four taxa increased to levels found in non·snail treatments. However, one diatom was more than twice as abundant in snail treatment over non-snail treatment -- apparently stimulated by the presence of snails during cold conditions; and two diaoms remained at low abundance in snail treatment despite rapid growth in non-snail treatment -- apparently inhibited or selected as a food source by snails during cold con- ditions. No algal taxa replaced the diatoms inhibited by 0.5 mg Zn•l⁻¹ in this October-November, 1984, experiment by day 10. This is in contrast to an experiment performed one month earlier, in September-October, in which a community characteristic of this treatment developed by day 5. Testing individual and combined variables that affect attached algal communities will enhance understanding of population dynamics in algal ecology and pollutant assessment. In the experiment presented in chapter 5, attached-algal communities were employed to test the US Environmental Protection Agency’s (USEPA) guidelines for zinc (Zn) and pH. The experiment was designed to determine whether algal community composition and abundance would be altered by (a) ph 6 or 9, (b) 0.05 mg Zn•l⁻¹, or (c) the combination of ph 6 or 9 and 0.05 mg Zn•l⁻¹. Stream mesocosms were continuously supplied with natural water from the New River, VA, USA. Established (12-day colonization) communities on artificial substrates were sampled on days 0, 5, 10, 20, and 30 after treatment began on 9 July 1985. Zinc and pH treatments changed algal community composition from diatoms and a filamentous blue-green alga to different diatom taxa, green algae, or a coccoid blue-green alga. Total algal abundance was moderately increased by pH 6 treatment. Treatments of pH 6 and 0.05 mg Zn•l⁻¹ significantly altered attached-algal community composition even though these levels are considered "safe' by the USEPA. The pH 9 treatment did not significantly alter community composition, most likely because ambient pH was near this level. / Ph. D. / incomplete_metadata

Bibliography: leaves 174-204. "This work provides a starting point for understanding the molecular mechanisms of zinc uptake and the regulation of zinc transport in cereals. Zinc efficient cereals would yield more on soild with low zinc and could potentially result in increased zinc content grain."