Thesis (Doctoral)--University of Stockholm, 1983. / Includes articles on which author's Review is based. Includes bibliographical references.

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One of the factors that affect the post-harvest behavior of seeds is provenance. Different geographical locations are characterised by different environmental conditions, hence, plant materials harvested from different locations may respond differently to laboratoryinduced stresses. The aim of the present study was to assess the role that provenance plays on the degree of recalcitrance of a single species – a factor that needs to be taken into consideration when choices are to be made for plant germplasm conservation. In this study, seeds of Trichilia dregeana, which have been shown to display recalcitrant post-harvest behavior, were harvested from four locations that were slightly different in climatic conditions: Mtunzini (MTZN), Durban (DBN), Pietermaritzburg (PMB) and Port Edward (P.ED), all within the KwaZulu-Natal province of South Africa. Clean seeds, whose aril and seed coat have been removed, were subjected to different drying and chilling stresses and their responses to the stresses are examined. Excised embryonic axes of the seeds were also subjected to flash (very rapid) drying and their responses to the stress are shown. Although the vegetation of these locations can be categorized as being sub-tropical, the present study suggests that there may be ‘degrees’ in the sub-tropical nature based on the rainfall and maximum temperature data. The ‘degree of sub-tropicality’ is suggested to be in the order MTZN > DBN > P.ED > PMB. Mean seed size assessed as seed length, width and fresh mass varied significantly across the four regions, with seeds from MTZN being the smallest and those from P.ED being the largest. The shedding water content of the embryonic axes of the seeds for 150 min. However, shoot production, root and shoot length and dry mass accumulation showed that axes of seeds from MTZN were the most adversely affected by rapid drying while those from PMB were the least sensitive. When clean whole seeds were dried slowly by burying in silica gel for 36 h, all seeds of the four provenances still retained more than 50% of their shedding water. MTZN seeds lost viability completely from the 24 h of slow drying while seeds from the other three locations retained some viability after 36 h. The order of survival of slow drying was MTZN < DBN < P.ED = PMB. Storage of cleaned whole seeds at chilling temperatures (3oC, 6oC and 16oC) caused increase in the water content of the embryonic axes of the seeds across the four locations. All seeds of the four provenances had lost more than 50% survival after they had been stored at 3oC for 10 weeks. Survival was completely lost from the 12th week for MTZN seeds, from the 14th week for DBN and P.ED seeds and from the 16th week for PMB seeds. There was no survival recorded for seeds across the four regions at the 18th week. The seeds were able to tolerate storage at 6oC for a little longer than those stored at 3oC. Only MTZN seeds completely lost viability at the 18th week; seeds from the other three locations retained some viability throughout the 18 weeks of storage. Storage at 16oC was the most tolerable, as all seeds from the four provenances maintained some viability until the 18th week in storage, with MTZN having the least survival and those from P.ED having the highest survival. Phylogenetic analysis of the internal transcribed spacer (ITS) region of the DBN and PMB samples showed intraspecific levels of genetic variation, and were separated by a genetic distance of 0.9%, an indicator that differences in storage behavior, chilling and desiccation sensitivity between seeds obtained from different collection localities may be genetically based. This study showed that MTZN seeds were the most sensitive, while seeds from PMB and P.ED were the most tolerant, to drying and chilling treatments, respectively. The prevailing climatic conditions may have a bearing on the responses observed in this study. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2011.

Bibliography: leaves 155-182. Most agricultural crop seeds are 'orthodox' ie. desiccation is a necessary feature of their complete life cycle. Low moisture content lengthens the storage life of orthodox seeds. Recalcitrant seeds, which do not tolerate low moisture content, lose viability in dry storage. The thesis studies the role of sugars in desiccation tolerance in developing seeds and investigates other mechanisms which might be involved in desiccation tolerance and desiccation sensitivity.

Desiccation-sensitive seeds show differential viability characteristics during drying at different rates. A number of studies have demonstrated that rapid dehydration permits survival to lower water contents than does slower desiccation. The aim and objective of the present study was to test the hypothesis which states that rapid drying of desiccation-sensitive seeds removes water sufficiently fast to reduce the accumulation of metabolic damage. In addition, the hypothesis that wet storage subjects desiccation-sensitive seeds to mild, but increasingly severe, water stress causing oxidative damage if additional water is not supplied, was tested. In the present study, axes of germinating orthodox seeds of Pisum sativum and newlyshed recalcitrant counterparts of Quercus robur, Strychnos madagascariensis, Trichilia emetica, Trichilia dregeana and Avicennia marina were subjected to rapid or slow drying or wet storage. For those species where more than one harvest was investigated, differences were observed in water contents at shedding. For all the species studied, the dehydration rate could be described by an exponential and a modified inverse function for both desiccation regimes, and the water content remained constant with wet storage. The level of tetrazolium staining and germination percentage of axes decreased sharply drying and hydrated storage such that the marked decline took place at lower water contents upon rapid than slow dehydration. The conductivity of electrolyte leachate increased progressively during desiccation and moist storage of axes of all species investigated. Greater membrane leakage occurred upon slow, than rapid dehydration in axes of all species studied. Activities of respiratory enzymes which have a potentially regulatory role in glycolysis, phosphofructokinase (PFK), or the tricarboxylic acid cycle, malate dehydrogenase (MDH), and levels of the oxidized form of the coenzyme, nicotinamide adenine dinucleotide (NAD), of the enzymes of the electron transport chain, NADH dehydrogenases ofNADH-ubiquinone (coenzyme Q) reductase (complex I) and NADHcytochrome c reductase (complex IV), were monitored in the present investigation. v In addition, the role of free radical activity in the form of lipid peroxidation, which has been implicated in loss of viability in seeds, was examined by assaying the levels of hydroperoxides. The involvement of the free radical processing enzymes, superoxide dismutase (SOD), catalase (CAT) and glutathione reductase (GR), and the antioxidant, ascorbic acid (AsA), was also ascertained. The activity of PFK in axes of P. sativum remained constant during drying and wet storage. However, PFK activity increased as rapid dehydration and hydrated storage of Q. robur axes proceeded. In contrast, the activity of PFK in axes of Q. robur decreased during slow desiccation. Similarly, PFK activity was reduced upon drying, and moist storage, of T. dregeana axes such that higher activity of PFK was seen during rapid than slow dehydration. The activity ofPFK inA. marina axes also declined upon desiccation. The activity ofMDH in axes of P. sativum was also unchanged during drying and wet storage. However, an increase in MDH activity was recorded in Q. robur axes during dehydration and hydrated storage such that the activity of MDH was higher upon slow than rapid desiccation. In contrast, MDH activity in axes of T. dregeana decreased as drying proceeded. Similarly, the activity of J\.1DH declined during dehydration and moist storage of A. marina axes. An increase in the level of NAD occurred in axes of P. sativum during drying. In contrast, a decrease in NAD levels was seen upon dehydration and wet storage of Q. robur axes such that the level of NAD was higher upon rapid than slow desiccation. There was an enhancement of the level of NAD in axes of T. dregeana during hydrated storage. Conversely, NAD levels declined during drying ofA. marina axes. A decrease in the level of hydroperoxides in axes of P. sativum was seen as rapid drying proceeded. In contrast, hydroperoxide levels increased during wet storage of P. sativum axes. Similarly, the levels of hydroperoxides were enhanced upon dehydration and hydrated storage of Q. robur axes such that they were higher in axes during slow desiccation compared to those dried rapidly. Conversely, the hydroperoxide level in axes of T. dregeana was reduced upon rapid dehydration. In contrast, an elevation of the level of hydroperoxides was observed during moist storage. The levels of hydroperoxides remained constant as desiccation and wet storage ofA. marina axes proceeded. vi The activity of SOD in axes of P. sativum decreased during rapid drying. In contrast, SOD activity increased upon slow dehydration and wet storage ofP. sativum axes. There was a decline in the activity of SOD in Q. robur axes during slow desiccation. Similarly, SOD activity was diminished upon drying of axes of T. dregeana. The activity ofSOD in T. dregeana axes was enhanced during hydrated storage. An elevation in SOD activity also took place during rapid dehydration and moist storage of axes ofA. marina. The activity of CAT did not change during drying of axes of P. sativum. However, a decrease in CAT activity in Q. robur axes was seen upon slow dehydration and wet storage. Similarly, the activity of CAT declined as desiccation of axes of T. dregeana proceeded. In contrast, CAT activity inA. marina axes increased during slow drying. Whereas the activity of GR in axes of P. sativum increased during drying and wet storage, GR activity decreased in A. marina axes upon all treatments such that the activity ofGR was higher during rapid than slow dehydration. GR activity also declined upon slow desiccation and hydrated storage ofaxes of Q. robur. Similarly, the activity of GR in T. dregeana axes was reduced during moist storage. Finally, a decrease in the level of AsA in axes of P. sativum took place during drying. Nonetheless, dehydration and wet storage of Q. robur axes were associated with no siginificant change in AsA levels. There was also a decline in the level of AsA in axes of T. dregeana as rapid desiccation proceeded. Similarly, a reduction in AsA level occurred upon slow drying ofaxes ofA. marina. The results presented here are consistent with the observation that drying and wet storage adversely affected the respiratory enzymes, PFK, MDH and NADH dehydrogenase. It is suggested that the resultant metabolic imbalance led to more leakage of electrons from the mitochondrial electron transport chain than normal, and through lipid peroxidation increased levels of hydroperoxides. In addition, dehydration and hydrated storage may depress the activities of free radical processing enzymes, SOD, CAT and GR and levels of antioxidant, AsA. This phenomenon was less pronounced during rapid, in comparison to slow, desiccation and moist storage. However, it appears that the above biochemical events are overtaken by physical damage at higher water contents in the highly recalcitrant seeds. It was concluded that the differential effects of VII the drying rate and wet storage on responses of desiccation-sensitive seeds varies with tissue, harvest, species and the degree of desiccation sensitivity. / Thesis (Ph.D.)-University of KwaZulu-Natal, 2004.

Bibliography: leaves 155-182. / xiv, 182, [10] leaves, [11] leaves of plates : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Most agricultural crop seeds are 'orthodox' ie. desiccation is a necessary feature of their complete life cycle. Low moisture content lengthens the storage life of orthodox seeds. Recalcitrant seeds, which do not tolerate low moisture content, lose viability in dry storage. The thesis studies the role of sugars in desiccation tolerance in developing seeds and investigates other mechanisms which might be involved in desiccation tolerance and desiccation sensitivity. / Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Science, 1996?

Thesis (PhD (Food Sc))--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Maize kernels consists of two types of endosperm, a harder vitreous endosperm and a softer floury endosperm, and the ratio of the vitreous and floury endosperm present mainly determines the hardness of the kernel. Maize (Zea mays L.) is a staple food in many countries, including South Africa, and is industrially processed into maize meal using dry-milling. For optimal yield and higher quality products, hard kernels are favoured by the milling industry. Despite many maize hardness methods available, a standardised method is still lacking, furthermore, no dedicated maize milling quality method exists. Using an industrial guideline (chop percentage), a sample set of different maize hybrids was ranked based on milling performance. Unsupervised inspection (using principal component analysis (PCA) and Spearman’s rank correlation coefficients) identified seven conventional methods (hectoliter mass (HLM), hundred kernel mass (HKM), protein content, particle size index (PSI c/f), percentage vitreous endosperm (%VE) as determined using near infrared (NIR) hyperspectral imaging (HSI) and NIR absorbance at 2230 nm (NIR @ 2230 nm)) as being important descriptors of maize milling quality. Additionally, Rapid Visco Analyser (RVA) viscograms were used for building prediction models, using locally weighted partial least squares (LW-PLS). Hardness properties were predicted in the same order or better than the laboratory error of the reference method, irrespective of RVA profile being used. Classification of hard and soft maize hybrids was achieved, based on density measurements as determined using an X-ray micro-computed tomography (µCT) density calibration constructed from polymers with known densities. Receiver operating classification (ROC) curve threshold values of 1.48 g.cm-3 , 1.67 g.cm-3 and 1.30 g.cm-3 were determined for the entire kernel (EKD), vitreous (VED) and floury endosperm densities (FED), respectively at a maximum of 100% sensitivity and specificity. Classification based on milling quality of maize hybrids, using X-ray µCT derived density and volume measurements obtained from low resolution (80 µm) µCT scans, were achieved with good classification accuracies. For EKD and vitreous-to-floury endosperm ratio (V:F) measurements, 93% and 92% accurate classifications were respectively obtained, using ROC curve. Furthermore, it was established that milling quality could not be described without the inclusion of density measurements (using PCA and Spearman’s rank correlation coefficients). X-ray µCT derived density measurements (EKD) were used as reference values to build NIR spectroscopy prediction models. NIR spectra were acquired using a miniature NIR spectrophotometer, i.e. a microNIR with a wavelength range of 908 – 1680 nm. Prediction statistics for EKD for the larger sample set (where each kernel was scanned both germ-up and germ-down) was: R2 V = 0.60, RMSEP = 0.03 g.cm-3 , RPD = 1.67 and for the smaller sample set (where each kernel was scanned only germ-down): R2 V = 0.32, RMSEP = 0.03 g.cm-3 , RPD = 1.67. The results from the larger sample set indicated that reasonable predictions can be made at the fast NIR scan rate that would be suitable for breeders as a rough screening method. / AFRIKAANSE OPSOMMING: Mieliepitte bestaan uit twee tipes endosperm, ‘n harder glasagtige endosperm en ‘n sagter melerige endosperm, en die verhouding waarin die twee tipes endosperm aangetref word, bepaal hoofsaaklik die hardheid van die pit. Mielies (Zea mays L.) is ‘n stapelvoedsel in baie lande, insluitende Suid-Afrika, en word industrieël geprosesseer na mieliemeel deur van droë-vermaling gebruik te maak. Vir optimale produksie en beter kwaliteit produkte, word harde pitte deur die meule verkies. Ongeag die beskikbaarheid van verskeie mielie hardheid metodes, ontbreek ‘n gestandardiseerde metode nog, en verder bestaan ‘n metode om mielies se maalprestasie te bepaal ook nie. ‘n Monsterstel, bestaande uit verskillende mieliebasters, is op grond van maalprestasie ingedeel deur van ‘n industriële riglyn (chop persentasie) gebruik te maak. Inspeksie sonder toesig (deur gebruik te maak van hoofkomponentanalise (HKA) en Spearman’s rangkorrelasiekoëffisiënte) het sewe onkonvensionele metodes (hektoliter massa, honderd pit massa, protein inhoud, partikel grootte indeks, persentasie glasagtige endosperm soos bepaal deur gebruik te maak van naby-infrarooi (NIR) hiperspektrale beelding en NIR absorbansie by 2230 nm) identifiseer as belangrike beskrywers van maalprestasie. Daarbenewens, is Rapid Visco Analyser (RVA) viskogramme gebruik om voorspellingsmodelle te bou deur gebruik te maak van plaaslik geweegte gedeeltelike kleinstekwadrate (PG-GKK) wat hardheidseienskappe kon voorspel met laer, of in dieselfde orde, laboratorium foute van die verwysingsmetodes, ongeag die gebruik van verskillende RVA profiele. Klassifikasie tussen harde en sagte mieliebasters was moontlik, gebasseer op digtheidsmetings soos bepaal met ‘n X-staal mikro-berekende tomografie (µBT) digtheids kalibrasie gebou vanaf polimere met bekende digthede. Ontvanger bedryf kenmerkende (OBK) kurwe drempelwaardes van 1.48 g.cm-3 , 1.67 g.cm-3 en 1.30 g.cm-3 is bepaal vir hele pit, glasagtige en melerige endosperm digthede, onderskeidelik, teen ‘n maksimum van 100% sensitiwiteit en spesifisiteit. Klassifikasie van die mieliebasters, gebasseer op maalprestasie en deur gebruik te maak van X-straal µBT afgeleide digtheid en volume metings soos verkry teen lae resolusie (80 µm) skanderings, was moontlik met goeie klassifikasie akkuraatheid. Vir heel pit digtheid en glasagtigtot-melerige endosperm verhouding metings is 93% en 92% akkurate klassifikasies verkry wanneer OBK kurwes gebruik is. Verder is dit vasgestel (deur gebruik te maak van HKA en Spearman’s rangkorrelasiekoëffisiënte) dat digtheidsmetings ingesluit moet word vir ‘n volledige beskrywing van maalprestasie. X-straal µBT afgeleide digtheid metings is gebruik as verwysings waardes om NIR spektroskopie voorspellings modelle te bou. NIR spektra is verkry deur van ‘n miniatuur NIR spektrofotometer, naamlik ‘n microNIR, bebruik te maak vanaf 908 – 1680 nm. Voorspellings statestiek vir die groter monsterstel (waar elke pit beide kiem-bo en kiem-onder geskandeer is) was vir HPD: R2 V = 0.60, RMSEP = 0.03 g.cm-3 , RPD = 1.67 en vir die kleiner monsterstel (waar elke pit was slegs kiem-onder geskandeer is) vir HPD: R2 V = 0.32, RMSEP = 0.03 g.cm-3 , RPD = 1.67. Die resultate van die groter monsterstel het aangedui dat redelike voorspellings moontlik is, teen die vinnige NIR skaderings tempo wat as rowwe vertoningsmetode geskik sal wees vir telers.

Typescript (photocopy). / Digitized by Kansas Correctional Industries

Managing cattle to disseminate seeds of desirable plants, or alternatively, to restrict weed seed contamination on rangelands is of interest to managers. Four experiments were conducted to determine effects of ruminant digestion on germination of ingested seeds. A number of plant species representing a variety of seed size and seed coat hardness were subjected to in vitro digestion. Experiment one was conducted to determine effect of varying lengths of digestion time on seed germination. Seed germination varied by plant species in response to length of digestion. Germination of large soft-coated seeds, such as bluebunch wheatgrass (Agropyron spicatum (Pursh) Scribn. & Smith Goldar) and basin wildrye (Elymus cinereus Scribn & Merril Magnar), was reduced to 0%. Smaller grass seeds, such as Sherman big bluegrass (Poa secunda Presl. Sherman), survived but germination declined following 24-hour, 48-hour, and 72-hour digestion. Experiment two examined effect of different stages of ruminant digestion on seed germination. The combination of Stage I (rumen-simulated digestion) and Stage II (abomasal-simulated digestion) resulted in greatest seed mortality. Two water treatments were included to evaluate the effects of high temperatures (39��C), moisture uptake, and lack of oxygen. Water + O��� and Water + CO��� reduced germination, however not as much as Stage I and Stage II treatments. The third experiment determined effects of diet quality on seed germination. Seeds digested in rumen fluid collected from steers fed a 72% corn concentrate diet resulted in 0% germination for all species. Grass seed germination was low for seeds digested in rumen fluid collected from steers fed a forage diet. Whitetop (Cardaria draba (L.) Hand.) germination was 24% and 28% for 35-hour and 59-hour roughage treatment, respectively, and germination was 0% for 35-hour and 59-hour concentrate treatments. Germination of water-only treatments for most species was reduced in comparison to the control treatment, but was greater than remaining treatments. Experiment four evaluated germination of seeds exposed to in situ versus in vitro digestion. In situ digestion resulted in lower seed germination than in vitro digestion for all species examined. Large, soft grass seeds may not be suitable candidates for reseeding rangelands. However, it is important for managers to recognize that cattle may distribute viable weed seeds in feces. Confining cattle or supplementing with high concentrate diets may help prevent spread of weedy species. / Graduation date: 1997