Thesis (MScAgric)--University of Stellenbosch, 2007. / Bibliography. Also available via the Internet.

Thesis (MSc.)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: Pinus patula is one of the most important softwood species planted in South Africa for fibre and timber production and also the main species to be planted in the North Eastern Cape managed by Mondi Forests. Pinus patula is an exotic species to South Africa and therefore only commercially exists in man made plantations. Transplants are being grown in containerised nurseries and flowing from this regime are root alterations with potential root deformity risks. Current difficulties include poor root development and instability. The so-called old land syndrome also occurs in old agricultural soils. In this study my objective was to investigate the extent of this problem and whether the problem could be solved by better silvicultural practises. Literature indicated that bad root development occurs within the period in which transplants are kept in the nursery. Old land soils have numerous possible variables that could be investigated and tested. Trials were conducted where different dimensions of transplants, cuttings and seed were planted under different soil, climate and chemical conditions. Root development, root weight, root growth potential, shoot growth and survival were measured in order to establish the ideal containerised seedling dimension for optimum survival and growth. Ideal growth conditions for optimal transplant and later tree development in old land soils were also determined. It was evident that smaller seedlings had better chances of survival and growth. The effects of container volume and dimension on root development were unfortunately not tested. My results indicated it a very important factor in root development. Taproots should not be pruned and the laterals should not start to grow in a horizontal circular direction, as it will cause an altered root development. Old lands do not have a single individual factor causing bad survival and growth but rather a combination of factors. Weed competition weakens the transplants and other detrimental factors such as pathogens, soil structure deterioration, sub standard transplants, toxins and soil nematodes aggravate matters. / AFRIKAANSE OPSOMMING: Pinus patula is van die mees belangrike sagtehout spesies tans aangeplant in Suid Afrika vir vesel en saaghout doeleindes. Genoemde spesie is die hoofspesie geplant in die studie area naamlik die Noord Oos Kaap bestuur deur Mondi forests. Pinus patula is ‘n uitheemse spesie en kom kommersieel slegs in plantasievorm voor. Saailinge word in houer kwekerye gekweek en wortel misvorming kan hieruit voortvloei. Swak wortel ontwikkeling en onstabiliteit is twee van die hoofprobleme wat met laasgenoemde ondervind kan word. Die sogenaamde oulandsindroom word in ‘n erge graad in die studie area ondervind My studie poog om die omvang van genoemde probleme te ondersoek en of die probleme opgelos kan word deur verbeterde boskultuurpraktyke al dan nie. Literatuur dui daarop dat die wortelmisvormingsprobleem hoofsaaklik spruit uit die tydperk waar die saailing in die kwekery deurbring. Die oorsaak van mortaliteit in oulande is ook ondersoek. Eksperimente is uitgele waar verskillende dimensies van saailinge, steggies en saad geplant en getoets is in verskillende grond, en klimaats toestande. Wortel ontwikkeling, wortel gewig, wortel groeipotensiaal, lootgroei en oorlewing is gemeet ten einde die ideale saailing dimensie en groeitoestande vir optimum oorlewing en groei vas te stel. Saailinge met ‘n kleiner dimensie het ‘n groter kans tot normale oorlewing en groei. Houerdimensie en volume is nie in hierdie studie getoets nie. Hierdie studie dui daarop dat houerdimensie en volume ‘n belangrike faktor is in die ontwikkeling van wortels. Die studie dui ook daarop dat dit belangrik is om nie in ‘n praktyk te verval waar die penwortel gesnoei word en laterale wortels horisontaal sirkelvormig begin groei nie. Genoemde sal wortel vervorming tot gevolg he. Geen enkel faktor kon vir die swak groei en hoe mortaliteit in oulande verantwoordelik gehou word nie maar wel ‘n kombinasie van kompeteerders. Onkruid kompetisie het wel die saailinge onderdruk en gevoelig gemaak vir ander ouland beperkings soos patogene, grondstruktuurverval, lae standaard saailinge, toksiene en grondnematode.

Pinus patula Schiede ex Schlect. & Cham. is the most widely planted softwood species for both pulpwood and saw timber in the South African forestry industry. High mortality of this species, often in excess of 20%, following planting is currently of major concern and has the potential to limit future deployment for commercial timber. Water stress is often reported to be a cause of mortality during regeneration in commercial forestry plantations yet, prior to 2007, there was no published research on the water relations of P. patula during regeneration in South Africa. This, together with questions raised by the industry as to the role of using water in the planting operation, initiated the series of studies conducted for this thesis. Water planting (application of water into the planting hole at the time of planting) of P. patula seedlings has been used commercially to reduce post-planting water stress and buffer against potentially extreme weather conditions immediately after planting. However, the primary role of the water, as well as its success in increasing survival following planting, has never been critically assessed. Since the use of water in the planting operation is expensive, it was essential that the benefits to using water were quantified, in terms of survival and growth, and justified, in terms of any monetary investment. In addition, there was a lack of local studies investigating the physiological characteristics of P. patula seedlings, particularly their tolerance to low soil water availability. To understand the role of water during the regeneration of P. patula in terms of plantation management and seedling physiology, a variety of research methodologies were used that included: applied field trials, multivariate methods (a retrospective investigation), pot trials and the development of a simple financial model. Four field trials were implemented to test the response in P. patula survival to water applied at planting. Two trials each were situated in the KwaZulu-Natal (KZN) Midlands and Mpumalanga Escarpment. The first trial at each site was planted in spring (October) and the second in summer (February). Watering treatments consisted of different quantities of water used in the planting operation and included 0.5 litres, 2 litres, 4 litres and no water (dry plant). Only at the spring planted trial in the KZN Midlands was survival of the dry planted seedlings significantly lower than that of the seedlings planted with water, at 90 days after planting. This may have been due to low rainfall during the week before and two weeks after planting, or the small size of the seedlings used in the trial. Application of 0.5 litres of water to the planting pit was sufficient to increase survival to a level equivalent to that where 2 or 4 litres of water was used, yet only increased soil moisture in the area immediately surrounding the seedling. This suggested that the role of the water applied during planting was increased root to soil contact. Overall, these four trials indicated that planting with water had the potential to increase survival only when soil water availability was low and rainfall sporadic. There was no effect of water applied at planting on early tree growth. While the results of the four field trials provided an indication of the effect of planting with water on subsequent survival of P. patula seedlings, there was concern that the results of the four trials may not be a true reflection of a dynamic situation. Survival in response to water applied at planting may vary from year to year and across forestry regions due to the unpredictable nature of rainfall and high air temperatures during the planting season, as well as the wide range of forestry sites across which P. patula seedlings are planted. To improve our understanding, a database of 58 trials was compiled where water and dry planting had been carried out. In this way it was possible to investigate whether the results from the four field trials were reflected in a range of previously conducted field trials implemented across time and space. The trials incorporated into the dataset were all planted to P. patula between 1990 and 2005 in the summer rainfall region of southern Africa. Data related to the climate, local weather, physiography and site management at each trial were also included. Summary statistics, linear correlation and multiple regression were used to determine if site-associated variables were related to an increase in survival in the water relative to the dry planted treatments. The analyses indicated that for all 58 trials, survival was lowest during the summer months, regardless of planting treatment. Planting with water was most likely to increase survival when used during spring, autumn and winter planting, although (as with the four applied field trials) there was no overall significant relationship between water planting and survival. Based on these results it was anticipated that an understanding of the water stress physiology of P. patula seedlings was required to explain the observed trends from a more fundamental perspective; if planting with water did not always increase survival, why not? Three pot trials were conducted to increase the understanding of the water relations of P. patula seedlings. These trials were also used to provide benchmark physiological data related to stressed (water) and unstressed seedlings. The first pot trial highlighted the importance of root plug moisture at the time of planting for increasing subsequent survival. The subsequent two pot trials were aimed at investigating the interaction between planting stock quality (as determined by measures of size) and soil water availability and the effect on survival, growth and physiology of P. patula seedlings. These results indicated that P. patula seedlings were not as sensitive to high air and soil temperatures (above 30°C) and low soil water availability (below -1.5 MPa) as previously thought. The seedlings were able to tolerate low soil water availability for several weeks and, following rewatering, were able to recover from moderate and severe water stress (a shoot water potential of below -1.5 MPa). This data supported the results from the four applied field trials and retrospective study of 58 trials, where the application of water to the seedlings at planting did not substantially increase survival. In the pot trials, stomatal conductance started to decrease when shoot water potential approached -0.8 to -0.9 MPa. Stomatal closure occurred at a shoot water potential between -1.2 MPa to -1.5 MPa. Mortality due to water stress occurred only in response to extended periods of low soil water and was associated with a shoot water potential of below -3.0 MPa. There was variability between seedlings in their potential for survival and growth. Inherently bigger seedlings had a greater capacity for new root growth following planting. New root growth, as well as a greater mass of new roots, was associated with higher shoot water potentials and higher rates of transpiration under conditions of low soil water availability. This indicated that seedling quality, as determined by size, may play a role in sensitivity to water stress. The field trials, retrospective study and pot trials indicated that the practice of planting with water was not always critical to the survival of P. patula seedlings. A simple financial model was developed to estimate whether planting with water represented a cost that could be used as a decision criterion, given certain growth parameters and management scenarios. The data projected by the model were also compared to actual research data for water versus dry planting (and the inclusion of an insecticide in the water). While these comparisons were specific to the parameters included in the model for this study, as well as the results of the research trials used in the benchmarking exercises, the model indicated that; 1) costs for planting with water were likely to be recovered only when no blanking (replacing of dead trees) was carried out, with capital invested at a low return rate (3%), 2) including an insecticide in the water increased the likelihood of cost recovery, and 3) site quality had an impact on the increase in survival required to recover planting method costs, with a greater percentage increase in survival required on lower quality sites. Lower quality sites often have a lower mean annual precipitation (associated with higher rainfall variability), or shallow soils (associated with lower soil water availability) and therefore are also likely to be sites where foresters may want to use water to reduce (drought related) mortality. The impact of site quality is thus also an important factor to include in any decisions regarding planting methods (i.e. using water) and their costs. Further investigations should be aimed at examining; 1) the interaction of root plug size (as determined by container type) and soil water availability on growth and physiology of P. patula seedlings, 2) the methods of grading seedlings within a population to select those that have a high potential for survival and growth, and 3) the effects of soil water availability on the physiology, survival and growth of P. patula cuttings, as well as other pine species and hybrids grown in South Africa, such as P. elliottii, P. elliottii x P. caribaea and P. patula x P. tecunumanii. It is likely that the proportion of forestry regions planted to these hybrids will increase in the future. / Thesis (Ph.D.)-University of KwaZulu-Natal, 2008.

No description available.

Immature, green female cones of Pinus patula Scheide et Deppe. were collected on a weekly basis during the South African summer months from December 1991 to February 1992 and from December 1992 to March 1993. Embryogenic tissue was initiated from excised megagametophyte explants containing immature zygotic embryos. Embryogenic induction was achieved using both MSG (BECWAR, NAGMANI & WANN 1990) and DCR (GUPTA & DURZAN 1985) media. The highest induction frequency was obtained on DCR1 (Douglas-fir Cotyledon Revised) medium supplemented with 0.5 mg 1 ¯¹ BA and 3.0 mg 1 ¯¹ 2,4-D, using L-glutamine as the major nitrogen source. Embryogenic tissue was translucent-to- white and mucilaginous in nature, composed of elongated, suspensor-like cells. The tissue was extruded from the micropylar end of the female gametophyte. In comparison, nonembryogenic tissue was produced from the gametophytic tissue itself and consisted of small, compact, spherical cells, crystalline in nature. Anatomical studies of developing patula seed demonstrated that the production of embryogenic tissue from the immature explants co-incided with the period, approximately two weeks after fertilization and with the occurrence of cleavage polyembryony in the developing zygotic embryos. Embryogenic tissue was maintained in culture by a recapitulation of the cleavage process. Transfer of the embryogenic tissue to DCR2 medium containing 1.3 mg 1 ¯¹ ABA resulted in tissue maturation and in the subsequent development of somatic embryos. Presence of ABA in the culture medium stimulated the development of cotyledonary initials in the apical region of the embryos. Elongated embryos, possessing small cotyledons, were rooted (50 to 60 %) on MSG6 medium containing no plant growth regulators. Somatic plantlets were successfully hardened-off under greenhouse conditions. Liquid culture methods were found to be a useful means of rapidly increasing the volume of embryogenic suspensor masses. Maturation , in terms of somatic embryo development and the production of cotyledonary initials, though , was not obtained in suspension. Reestablishment onto agar-solidified medium (DCR2) was required before maturation could occur. ABA is also responsible for stimulating reserve deposition and mobilization. In this regard, lipid accumulation in the developing somatic embryos was quantified and found to be significantly lower than in developing zygotic embryos. Similarly, non-matured embryogenic tissue contained less lipid deposits than matured (ABA-treated) tissue, indicating the requirement for ABA during maturation. Quantification of the lipids deposits is useful in determining the potential for somatic embryos to acclimatize to ex vitro conditions since their further growth and development is based on their ability to accumulate storage reserves. Somatic embryogenesis was found to be a useful method of propagation, producing plantlets with seedling-like qualities. This development has important consequences for the production of clonal plantlets in the Forestry Industry. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1994.

A study of factors contributing to successful controlled pollinations of Pinus patula Scheide et Deppe was undertaken. The pollen morphology of P. patula, P. oocarpa, P. greggii, P. elliottii, P. tecunumanii, P. caribaea and P. radiata was studied and the mean size of pollen grains was determined for these species. Clonal differences in pollen size within P. patula were also determined. The impact of pollen management practices on pollen viability was highlighted and a protocol for in vitro pollen viability testing of P. patula and other pine species was determined. A one percent agar solidified distilled water medium gave the best germination results after 72 hours incubation at 30 °C for a number of different Pinus species and P. patula clones. The addition of boric acid increase germination, although not significantly. The addition of sucrose to the pollen germination medium had a negative effect on pollen germination of P. patula, P. greggii and P. caribaea. Re-hydration of pollen for two hours prior to in vitro germination testing improved germination significantly. Incubation temperatures of above 38 °C were detrimental to germinating pollen grains. Stored pollen with low humidity (less than 10 %) of P. patula, P. greggii and P. caribaea could tolerate temperatures of up to 70 °C while still retaining some level of viability. The initiation and growth of the pollen tube was also studied and differences in pollen tube-lengths germinated at 30 °C for 72 hours were found between species studied. Flowering of different P. patula clones was monitored over seven seasons. Flowering periods varied in length between 4 and 14 days amongst five clones over the different seasons. The best cone-survival after controlled pollination was achieved with breathable micro-fibre material. Seed yields were also highest when breathable material was used for controlled pollination. The role of pollen viability in controlled pollination was also determined in pollination studies with low viability resulting in low cone survival and low seed yields. The temperature and relative humidity inside isolation bags were monitored and temperatures above 40 °C were reached inside bags constructed of nonbreathable material. These temperatures were lethal to pollen germinating in vitro. Relative humidity of between 80 and 100 % was maintained in non-breathable bagging material, constituting a risk of diseases causing cone-mortality. The application of fungicide before, during and after controlled pollination was ineffective in improving cone survival. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2002.

The major focus of this study was to provide better understanding of the potential of / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2007

Summary: The future mass propagation of elite families of Pinus patula by cuttings is a realistic method of deployment if the short-term performance of cuttings and seedlings are confirmed at harvesting. This will impact significantly on the future outlook of forestry in South Africa as softwood yields are improved substantially through the introduction of material of high genetic value in commercial plantings. This, however, will require significant changes in future silviculture and other management practices as foresters and plantation staff learn to regenerate, maintain, and schedule the harvesting of cutting stands according to a different set of demands as a result of the change in plant type. Contrary to operational experience, cutting survival was similar to seedling survival in all field studies. This indicates that factors other than those that were studied and reported on, such as planting techniques, may be contributing to mortality. Also, due to the different root structure of cuttings they may be more fragile. The similar survival observed in these trials, therefore, may have been due to the close supervision given to the planting operations by the research staff. Although survival was similar, both plant types survived unacceptably poorly in the majority of studies with an average stocking of approximately 50% at one year. It is therefore anticipated that commercial stands will require several blanking operations in order to achieve an acceptable stocking in excess of 85% by the following planting season. The reduction in expected profitability as a result of blanking costs, delayed establishment, and the loss of improved genetic plant material, indicates that this is an area that still requires further research irrespective of what plant type is being planted. The pathogen, Fusarium circinatum, was commonly isolated from the planting stock before and after planting in two studies. Due to its virulent nature, it was assumed that mortality on the trees on which F. circinatum was isolated was principally due to this pathogen. At planting all plants were observed to be healthy and free of disease indicating that this pathogen maybe carried from the nursery to the field in a cryptic form, either inside or outside the plant tissue , which results in the death of the newly planted tree. In two field studies, where F. circinatum was commonly isolated, the application of Benomyl fungicide and to some extent the biological control agent Trichoderma harzianum at planting appeared to improve survival although this improvement was not significant. Laboratory studies, designed to determine alternatives to Benomyl fungicide, indicated that three fungicides (Octave, Folicur and Tilt), three sterilants (Sporekill®, Prasin®and Citex®) , as well as a biological control agent (T.harzianum), were all highly successful in controlling F. circinatum colony growth in vitro. It is recommended that these products undergo nursery testing , where the plant material is inoculated with F. circinatum spores, in order to test their efficacy and possible phytotoxicity in vivo before commercial application. Post-planting survival was also affected by site climate . Greater temperature extremes, as well as lower humidity and less rainfall resulted in poor survival. Plant dimension at planting was found to interact with site quality where it was a significant factor on a poor quality site. Optimal cutting dimensions at planting was a root collar diameter of 2.8 - 3.2 mm, and a stem height greater than 7 cm at planting for cuttings produced in cavities 90 ml in volume. Optimal seedling dimensions at planting were a root collar diameter of 1.8 - 2 mm, and a stem height of 10 - 15 cm for seedlings produced in cavities 80 ml in volume. In a separate study, plant morphological criteria influenced medium-term growth, where greater root mass and thicker cutting root collar diameters at planting improved field growth performance for seven years after planting. A greater root mass at planting was achieved by raising cuttings in containers that could support greater medium volume. From the study it was concluded that cuttings should be raised for an approximate period of 9 months in container cavities no smaller than 80 ml in volume and possess an oven-dry root mass of 0.3 - 0.5 g at planting. In addition to similar survival, the cuttings in this study grew either similarly to, or in some cases out-performed, the seedlings that were used as a control. Several other published studies indicate that hedge maturation poses the greatest threat to the success of softwood cutting deployment. This is especially true in clonal forestry and methods to maintain juvenility, such as cold storage of shoots and cryopreservation, require further research before clonal plantations of P. patula can be realised. In the studies carried out on family hedges in this report, the effect of donor hedge maturation was found to influence nursery management practice and the characteristics of rooted cuttings. The nursery data indicates that rooting efficiency, root system quality, and stem size and form, all decline with increasing hedge age particularly from two years after the date of sowing. A decline in root system quality was particularly apparent and was observed prior to a decline in rooting efficiency. If field trials indicate poorer performance from older hedges , it may be necessary to determine whether the causes are purely ontogenetic, morphological, or both before drawing final conclusions about hedge longevity. Until such results are known, it is recommended that P. patula cuttings should be propagated from seedling donors maintained as hedges , approximately 15 cm high, for a period not more than three years from the date of sowing. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2005.

Thesis (M.S.)--Oregon State University, 1990. / Typescript (photocopy). Includes bibliography (leaves 64-67). Also available on the World Wide Web.

Thesis (MSc)--University of Stellenbosch, 2005. / Bibliography. Also available via the Internet.