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Item Some physiological effects of the herbicide bromacil (5-bromo-3-sec-butyl-6-methyluracil) on Asparagus officinalis L. : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science at Massey University(Massey University, 1985) Balasingam, GodwinThe root-absorbed, photosynthesis-inhibiting herbicide bromacil (5-bromo-3-sec-butyl-6-methyluracil) was applied in sand culture to tissue-cultured 18-month-old Mary Washington 500W clone of Asparagus officinalis L. grown under controlled environmental conditions. Dose-response characteristics were determined and ED₂⁰ and ED⁵⁰ values computed by regression analysis for several parameters for asparagus plants exposed to a single application of 0, 2, 4, 8, 16, 32, 64, 128, 256, and 512 p.p.m. bromacil in non-draining pots. The results of this initial broad spectrum studies revealed a drastic decline in visually assessed foliage damage score, shoot growth and root fresh weight, and an increase in shoot death at relatively low concentrations. Good dose-response characteristics were obtained, and time-course data showed that the rate and severity of effects increased with increasing dose. The ED⁵⁰ values 18 days after treatment were: visually assessed damage score, 2.7 p.p.m.; shoot growth, 25 p.p.m.; shoot death, 4.6 p.p.m.; and root fresh weight, 2.1 p.p.m. A catalogue of colour plates showing visual phytotoxic effects was compiled. The injury symptoms observed were: yellowing of cladophyll tips followed by bleaching with the effects extending towards the base, cladophyll tipping and progressive cladophyll death leading to shoot death. Equal increment dose-response experiments were conducted at 0, 2, 4, 6, and 8 p.p.m. bromacil, using a portable fluorometer (Model SF-10) to obtain fluorescence emission measurements. The results showed a dramatic decline in the initial rise in fluorescence yield from the cladophyll tips 156 hours after treatment. The ED⁵⁰ value was computed to be 2.3 p.p.m. Fluorescence emission measurements from cladophyll tips from excised shoots placed in bromacil solution at the same concentrations showed a dramatic decline in fluorescence yield within 17 hours indicating that uptake and translocation was more rapid without the roots. No significant changes in chlorophyll a, chlorophyll b and total chlorophyll concentrations, as determined by 80% acetone extraction technique, were evident in the samples in which a dramatic decline in fluorescence yield occurred. The results of this study, conducted under controlled environmental conditions, showed that the asparagus clone tested readily absorbed bromacil through its roots and translocated it to the foliage causing severe initial damage to the photosynthetic apparatus followed by detrimental effects on other parameters such as shoot growth, root fresh weight and shoot death. Even at a bromacil concentration of 2 p.p.m. the asparagus plants were found to susceptible to herbicide damage.Item Studies with the asparagus "mother fern" culture in a temperate climate : a thesis presented in partial fulfilment of the requirements for the requirements for the degree of Master of Applied Science in Plant Science at Massey University(Massey University, 1997) Lekholoane, Lekholoane IgnatiusIn temperate regions, asparagus is normally harvested in spring. An extended harvest season could prolong the supply of fresh asparagus and perhaps lead to an economic gain through high off-season prices. High production costs and low yield of some alternative strategies compared to the normal spring harvest seem to discourage their commercial use. However, field investigations on the mother fern system in a temperate climate have not been done. From 1995 through to 1996, field and controlled climate growth cabinets studies were conducted to evaluate the asparagus mother fern system in New Zealand. Separate field experiments, for UC 157 and Rutgers Beacon were carried out. Harvesting treatments were, normal spring harvest (September-early December) and two mother fern treatments, run from October-March and December-March. The carry-over effects of the experiment was determined in the spring of 1996, when the crop was harvested for one month (September-October) using the normal spring harvest system only. In the field study, peak spear production occurred in early December and mid-January, for normal spring harvest and mother fern treatments, respectively. Production of spears declined steadily from January to the end of March. The mother fern treatments resulted in a harvest season, which was 15 weeks longer than the normal harvest. However, the total-, marketable- and cumulative yields, and mean spear weight were significantly lower than for a 'normally' harvested crop. The normal spring harvest produced thicker and heavier spears than mother fern treatments. Spears from the latter were also more seedy than those from normal harvest. Environmental factors (insufficient moisture level, decreasing temperature) and possibly correlative inhibition may have been the causes of the reduced production of the mother fern system. UC 157 produced higher yields than Rutgers Beacon. The latter produced a large number of thin spears, which resulted in a high rejection rate. The follow up experiment did not show any marked treatment differences in total yield and number of spears. The experiment conducted in controlled climate growth cabinets studied the effects of temperature and harvesting systems (normal harvest and mother fern system) on spear and fern growth. Potted, one-year old plants, cvs. UC 157 and Jersey Giant, were grown at constant temperatures ranging from 15°C to 35°C at increments of 5°C. Spears (>8mm basal diameter, with closed tips) were harvested from these plants and used to visually assess postharvest shelf life at 20°C. The relative spear growth rate, spear production rate per plant increased with rising temperature from 15°C through to 30°C, beyond which they declined. Relative spear growth rate, spear production rate per plant and average basal spear diameter of mother fern plants were lower than for those under the normal harvest. Average spears diameter did not show any trend with respect to growing temperature. Correlative inhibition and respiratory activity of the fern, including the production of new roots and buds may have led to a reduction in reduced performance of the mother fern plants. The relative spear growth rate of Jersey Giant was higher than UC 157. The postharvest storage life of spears stored at 20°C in unperforated polythene bags averaged seven days. Growing temperature, harvesting system, cultivar did not influence the storage life of spears.Item Growth and physiological responses of asparagus (Asparagus officinalis L.) at high temperatures : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Horticultural Science at Massey University(Massey University, 1993) Yen, Yung-FuAsparagus is now planted in tropical climates, hence a series of experiments were carried out to examine the physiological responses of asparagus to high temperature. These included analysis and modelling of growth, and the measurement of heat tolerance of four asparagus cultivars at high temperatures. Asparagus seeds of four cultivars were sown and grown in controlled climate rooms. These results showed that growth of young asparagus plants was exponential, and thus the parameters RLGR (relative leaf area growth rate), RFGR (relative fern dry weight growth rate), RCGR (relative crown dry weight growth rate), RPGR (relative total plant dry weight) were constant for any specific temperature regime or cultivar. The growth rate could be classified according to the parameters NAR (net assimilation rate), LAR (leaf area ratio) and RGR (relative growth rate), and could be grouped into high : 'D25/N25°C and D30/N30°C', normal : 'D20/N20°C, D30/N20°C, D35/N15°C, and D35/N25°C', and poor growth rates : 'D35/N35°C, D40/N20°C, and D40/N30°C'. The effects of these temperature regimes on growth were greater than the differences among cultivars, although there were different responses at high temperature among cultivars. Generally, NARs decreased with increasing age, while LARs increased with age. Both NARs and LARs varied with temperature regime, plant age and cultivar. The effects of high temperature on NAR or LAR were greater than the differences between cultivars. The leaf production rate was the largest contributor to total plant relative growth rate, followed by the root, the stem, and the rhizome production rate. The stem and the rhizome production rates declined with age, the leaf production rate increased, and the root production rate was maintained nearly constant. The allometric coefficients of root in relation to fern for cultivars and for the various temperature regimes were essentially the same. On the contrary, the allometric intercepts between plants at various temperatures or between cultivars were significantly different, with Tainan No.1 having the highest and Larac the lowest root/ shoot ratio except at supra-optimal temperatures. The lower temperature regimes had the higher root: shoot ratios. The root: shoot ratio was higher with a 10°C day/night temperature differential compared to the equivalent constant temperature regimes. Day or night temperatures around 26.5°C were optimal for RLGR, RFGR and RPGR, but a night temperature of 23.8°C was optimal for RCGR. The experiment on spear yield and fern development showed that not only did high temperature depress spear yield and quality, but it also depressed total fern weight and individual fern height. The plant characteristics such as the first branch height and fern height were also depressed at high temperature. Brocks and UC157 maintained better fern characteristics than the others at high temperatures. From the parameters of Richard's equation on fern, and of the RSGRs on spear, the ability of adaptation to high temperature was in the order: Tainan No.1 > Brocks > UC157 > Larac. In a high temperature study with germinated asparagus seedlings, the higher the temperature was the more stunted the growth. High concentrations of ABA application also markedly depressed seedling growth. There was an additive effect of heat stress and application of high ABA concentration on seedling growth, while there was an ameliorative effect with the application of ABA at a low concentration (0.1 - 1 μM) on heat stressed seedlings. At high temperature the sensitivity difference to ABA between cultivars was clearly expressed and thus the difference in heat tolerance of asparagus cultivars may be determined by ABA insensitivity. The studies of the effect of high temperature on endogenous ABA levels showed that the endogenous ABA levels decreased with temperature and then increased to a peak around 38°C for Larac and Tainan No.1, but peaked at around 36°C or lower for Brocks and UC157 for both roots and shoots. The spears of Tainan No.1 had an extremely high ABA content at 28°C and 33°C and fell to similar levels as the other cultivars at 36°C. It is concluded that the peak of endogenous ABA occurred at supra-optimal temperature and then decreased to low levels at extreme high temperatures. The assay of membrane thermostability (Tm) is a potentially valuable means of determining heat tolerance of asparagus. Tm varied with genotype, age, and heat acclimation. Heat acclimation may increase the membrane thermostability of young tissues. UC157 may be expected to be best adapted to tropical climate on the basis of membrane thermostability, because UC157 had the highest Tm of spears grown at high temperature. Tainan No.1, Larac and Brocks grown at high temperature also had increased heat tolerance, presumably due to heat acclimation. The study on the differences between cultivars in heat shock protein production showed that changes in protein synthesis occurred when asparagus was heat shocked at 34°C or 37°C for 2 or 6 hours. Specific heat shock proteins were produced and the levels of normal proteins changed. Most of the HSPs were of low molecular weight (about 24 kD to 13 kD). A small number of the HSP's appeared to be cultivar specific. A number of ABA induced proteins might be HSPs, but ABA also depressed the production of some HSPs. However most HSPs were induced at high temperature even in the presence of ABA.Item Effects of temperature on seasonal changes in growth and carbohydrate physiology of asparagus (Asparagus officinalis L.) : a thesis presented in partial fulfilment of the requirements for the degree of Doctorate of Philosophy in Plant Science at Massey University(Massey University, 1992) Hughes, Avis RosalieIn a temperate climate, most of the visible, seasonal changes in asparagus growth are induced by or dependent on changing temperature regimes. Senescence of ferns in autumn occurred below 13C, but was prevented by 20C. Crowns required chilling at temperatures below 12.5C to release the internal dormancy which occurred during winter. Although budbreak was never completely suppressed, the minimum temperature at which budbreak could occur changed during winter dormancy. Budbreak did not occur at 12.5C in some cultivars at maximum dormancy. The optimum temperature for the growth of young plants was between 25C and 30C. A model was developed which simulated seasonal changes in carbohydrate accumulation and utilisation, and the changing source-sink relationships within male and female plants. The model used temperature, indirectly, to determine the times at which seasonal changes in plant growth occurred. The basic unit for carbohydrate production and allocation in cultivars with well defined rhizomes, e.g.'Rutger's Beacon', was a rhizome and it's attached developing axillaries. An axillary rhizome became independent very soon after it had developed fern. The basic unit may differ in cultivars such as 'UC157' which have less well defined rhizomes. The strength of correlative inhibition within a cultivar appears to affect both rhizome morphology and budbreak patterns during spear harvest. In summer, young fern had a higher mobilising ability for assimilate than older fern or roots in male plants. In late summer-early autumn, roots became a stronger sink than the fern. On female plants, reproductive sinks (i.e, berries) had the highest competitive and mobilising ability. Crown carbohydrate concentration appeared to reach a physiological maximum of 65% in late summer. Most of the carbohydrate pool was long chain fructans, i.e, with degree of polymerisation above eight. The size of the crown carbohydrate pool increased during autumn and senescence as crown dry weight increased. The concentration of disaccharide increased during senescence indicating that it may have a role in cold tolerance. There was little change in crown dry weight or carbohydrate concentration of chilled plants until after the plants had been chilled for five weeks and the minimum temperature for budbreak had decreased. Respiration then increased as internal dormancy was further released. Changes in the composition of carbohydrate reserves are associated with the chilling process, and may affect the release of internal dormancy. Dormant plants required exposure to temperatures below 12.5C to increase the monosaccharide concentration above 4.5% dry weight and to depolymerise long chain fructans. Both these factors would decrease the substrate for some energy requiring process which must occur before budbreak can occur. 'Rutger's Beacon' required approximately 500 chilling units (calculated using the Utah model) to release 50% of the basal buds from internal dormancy and permit growth at 12.5C. The chilling response curve for asparagus appears to be flatter than the Utah model. This thesis confirmed earlier work which indicated that improved agronomic performance may be related to increased partitioning into carbohydrate storage tissue i.e, the crown. Genotypic differences in depth of internal dormancy and spear growth rate will also affect yield. Differences in carbohydrate metabolism are not the reason for agronomic differences between male and female plants. The strong sink effect of berries on female plants reduces crown dry weight and thus the crown carbohydrate pool.Item Growth in the field and CO2 exchange characteristics in relation to temperature of young asparagus (Asparagus officinalis L.) : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Horticultural Science at Massey University(Massey University, 1993) Sudjatmiko, Sigit; Sudjatmiko, SigitStudies on asparagus plants were conducted in the field and in growth rooms during 1990 to 1992. The field experiment was carried out to study the growth and development of young asparagus using successional plantings, from September to March, with two commonly grown cultivars, namely UC157 and Jersey Giant. The growth room study was divided into three separate experiments with the following four cultivars: UC157, Brocks, Tainan 1 and Larac. The first experiment studied the effects of high temperatures (30/20, 35/25 and 40/30°C) on the ontogenetic changes of photosynthesis, the second the effects of temperatures (20/20, 25/25, 30/20, 35/15 and 40/20°C) on plant respiration and ACi curve. The final experiment examined the effects of high temperatures (20/20, 25/25, 30/20, 35/15 and 40/20°C) on the light response curve. In the field experiment, a logistic model based on a heat unit time scale was used to describe changes in total, crown and shoot dry weight. The curves showed that the earlier plantings resulted in larger plants at the end of the season. UC157 performed best from the September planting, while Jersey Giant suffered from low temperatures resulting in the differences between the September and October plantings being marginal. In addition, plant dry weight at the final harvest (autumn) decreased as the planting date was delayed. Planting later than October resulted in inferior plant quality based on carbohydrate storage and shoot, bud and root numbers criteria. In general the effect of treatment was carried over into the spring. A sharp decrease in total plant RGR late in the season was due, in particular, to the fall in shoot RGR. The fall in the shoot RGR was greater than the fall in crown RGR. The shoot to root dry weight ratio in the first season increased up until February and then decreased regardless of planting date and cultivar. The allometric relationship between shoot and crown dry weight showed a similar trend. It was suggested that the change in the ratio and in the allometric relationship was due to a seasonal factor, probably temperature. In early spring of the second season the ratio increased for a short period of time and then decreased or stabilised. Shoot, bud and root production increased exponentially for earlier plantings, particularly for UC157. UC157 had a higher number of these three plant parts than Jersey Giant. However, Jersey Giant had larger shoots, buds and roots as the total dry weights of these organs were not different to UC157. The bud to shoot number ratio increased as the season progressed suggesting that shoot growth predominated over bud production during early growth. Meanwhile the cumulative shoot plus bud to root number ratio was high and similar for all plantings during early growth suggesting that young plants gave priority to shoot and bud development. The ratio then decreased sharply before stabilising late in the season. At the final harvest the cumulative shoot plus bud was supported by about two roots for the early plantings. The CO2 exchange studies of asparagus seedlings found that maximum photosynthesis was achieved on fern of an intermediate age regardless of cultivars. Photosynthesis of young and mature ferns was similar. Photosynthesis decreased as temperature increased from 20 to 40°C. Brocks had a lower photosynthesis at 20/20°C compared to Tainan 1 and Larac, while at high temperatures both Brocks and UC157 had a higher photosynthetic rate than Tainan 1 and Larac. Shoot and crown dark respiration all increased with temperature but the Q10 was low. The low Q10 of crown respiration was possibly due to low oxygen availability and the capacity of storage roots to conserve storage carbohydrate. The fern photorespiration and dark respiration also increased with temperature, but at 40/20°C the photorespiration rate decreased. The decrease suggests that photorespiratory enzymes are labile to temperature compared to dark respiratory enzymes. There was a trend for Brocks to have a higher photorespiration rate compared to Tainan 1 and Larac at 20/20°C, while at 35/15°C the photorespiration rate of Brocks was lower compared to the other cultivars. The CO2 compensation point (Γ) increased as the temperature increased. The increase was mainly due to photorespiration but at 40°C dark respiration made a more significant contribution. The carboxylation efficiency (CE) was the major limitation at low temperature but as temperature increased stomatal limitation (1g) became an important factor. The increase in 1g was possibly due to the effect of a high VPD. Mature fern photosynthesis responded biphasically to increasing light intensities. The only difference in the light response curve between cultivars was at 35/15°C, where Brocks had a higher rate of photosynthesis than other cultivars at light intensities ranging from 300 to 750 μmol m-2 s-1. Furthermore, the quantum yield (α) and maximum photosynthesis at light saturation (Pmax) decreased and the light compensation point (LCP) increased as the temperature was raised. Tainan 1 had a higher LCP and lower α than other cultivars, while UC157 had a higher Pmax. Thus overall decrease in carbon accumulation with temperature was mainly due to an increase in stomatal limitation, a decrease in quantum yield, an increase in photorespiration (low carboxylation efficiency), and an increase in dark respiration.Item Asparagus somatic embryogenesis : detection of somaclonal variation using molecular and cytological analyses : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Horticultural Biotechnology at Massey University(Massey University, 1998) Hollingsworth, Wendy; Hollingsworth, WendyThe embryogenic potential for six asparagus cultivars (Aspiring, Karapiro, Pacifica, Turoa, Syn4, and UC157), and the genetic stability of the somatic embryogenic system were investigated. Experiments 1 to 3 investigated the embryogenic potential of select cultivars, whereas experiments 4 to 7 analysed the genetic stability of embryogenic cells and plantlets. In experiment 8, morphological, anatomical, cytological and molecular techniques were used to characterise different types of calli identified during the study. For all cultivars, embryogenic callus was promoted on Murashige and Skoog (MS) media containing 3% sucrose, 1% agar and one of the following plant growth regulator (PGR) concentrations: 0.3, 1, 3, and 10 µM 2,4-D and 1.0 µM NAA/ 0.1 µM Kinetin. Plant genotype, PGR concentration and length of time in culture significantly influenced both the number of explants producing calli and the type of calli developing from explants. The following sequence was found to be most effective in producing complete plantlets from embryogenic calli: callus induction (CI) on Murashige and Skoog (MS) media containing 3% sucrose, 1% agar and either of 1.0, 3.0 and 10 µM 2,4-D, followed by transfer onto liquid embryo induction media (EI) containing MS + 6% sucrose and finally regeneration on regeneration media (Rg4) containing MS + 0.2 g/l glutamine + 3% sucrose + 1% agar. Treatment of 'Pacifica' globular embryos at -15°C for 3 hr produced the highest percent converted plantlets (34 and 26% for 6-month-old embryogenic calli and 1 year-old embryogenic suspension cells respectively). The number of in vitro-regenerated asparagus plantlets surviving acclimatisation was increased by acclimatising plantlets with minicrowns that contain 2-5 storage roots, and by removal of in vitro-formed cladophylls prior to acclimatisation. Random amplified polymorphic DNA (RAPD) markers distinguished among asparagus cultivars, and revealed differences within seed-raised commercial cultivars. The RAPD technique also detected changes in genomic DNA structure induced during culture of embryogenic cells. No change in genomic structure of plantlets regenerated from somatic embryos was detected. Cytological analysis, using chromosome counts and DNA content analysis, were used to determine the genetic stability of embryogenic calli, suspension cells, and plantlets regenerated through somatic embryogenesis. The basic chromosome number of 20 (2n = 20) remained unchanged for all samples. The DNA content of explants and plantlets was similar, indicating that plantlets were diploid. The experiment was unable to detect somaclonal variation, revealed by altered ploidy level indicating that cytological analysis is not as sensitive as RAPD analysis for detecting somaclonal variation. Extracellular protein profiles generated for embryogenic cells grown in suspension culture were influenced by PGR concentration and length of time in culture, and were therefore not suitable for monitoring somaclonal variation. Overall, individual cultivars produced between 6 to 8 different calli types for all PGR treatments. Plant genotype and PGR treatment influenced the phenotype of calli developed for each cultivar. The results indicate that, for the six asparagus cultivars investigated in this study, nodular calli or nodular mucilaginous calli have more embryogenic potential than other calli types. These calli were also noted to produce embryogenic cells in suspension, and could, therefore, be used to successfully inoculate liquid cultures either for small or large-scale production of asparagus somatic embryos.