N. J. Taylor

• PhD (Horticultural Science)
• Senior Lecturer at University of Pretoria

The current rapid increase in ambient carbon dioxide concentration ([CO 2 ]) and global temperatures have major impacts on the growth and yield of crops. Potato is classified as a heat-sensitive temperate crop and its growth and yield are expected to be negatively affected by rising temperatures, but it is also expected to respond positively to inc...

Thermal remote sensing has been introduced as a robust technology for monitoring water status in plants, in a real-time and non-destructive approach, under a variety of environments. Canopy temperature is a key indicator of water stress and is extensively used for the determination of the water status in crops. A previous planting date study conduc...

Rosellinia necatrix is the causal agent of white root rot (WRR), a fatal disease affecting many woody plants, including avocado (Persea americana). As with other root diseases, an integrated approach is required to control WRR. No fully effective control methods are available, and no chemical or biological agents against R. necatrix have been regis...

Macadamia F. Muell is a recently domesticated nut crop characterized by a certain amount of drought tolerance. Whilst stomatal regulation of gas exchange and water relations has been documented in macadamia, there are no reports on non-stomatal limitations to photosynthesis and if changes occur over a season in relation to different phenological st...

Exceptionally high yielding (>100 t ha⁻¹) apple orchards (Malus domestica Borkh.) are becoming common in South Africa and elsewhere in the world. However, no accurate quantitative information currently exists on the water requirements of these orchards. Information is also sparse on the water use of young apple orchards. This paucity of data may ca...

Subtropical fruit crops form an important part of the fruit industry in many countries. Many of these crops are grown in semi-arid regions or subtropical regions where rainfall is seasonal and as a result the vast majority of these perennial, evergreen orchards are under irrigation. This represents a significant irrigation requirement and with more...

Apple production for the export market is in South Africa entirely dependent on irrigation. In recent years, high performing orchards yielding up to 120 t of fruit ha-1 are becoming common in a country where the average yield is between 60 and 80 t ha-1. This raises important questions regarding the sustainability of the exceptionally high yields g...

The accurate estimation of evapotranspiration (ET) of orchard crops is critical for judicious irrigation water management and planning. However, it is impossible to measure ET under all possible combinations of climate and management practices, which necessitates the use of ET models. Although empirical models are more likely to be adopted by consu...

Wheat straw has generally been used as the main substrate for cultivating oyster mushrooms (Pleurotus ostreatus); however, in South Africa it is becoming expensive for small-scale farmers to utilise. Therefore, the main objective of the study was to investigate the use of alternative, but suitable substrates for planting oyster mushrooms. Wheat str...

The effect of four different mulches on fruit quality was quantified, either directly via mineral nutrient contributions or indirectly, by increasing nutrient uptake efficiency in the soil. We hypothesised that fruit nutrient levels would increase more when an organic mulch, containing nutrients, was applied to the soil, with smaller/no increases w...

Agriculture, as the largest user of fresh water worldwide, is under close scrutiny to justify its use of water due to the increase in competition from a number of end-users. Apart from on-farm measures to increase water use efficiency, government intervenes through policy instruments to influence water use behaviour. Citrus growers need to take hee...

The estimation of crop water use is critical for accurate irrigation scheduling and water licenses. However, the direct measurement of crop water use is too expensive and time-consuming to be performed under all possible conditions, which necessitates the use of water use models. The FAO-56 procedure is a simple, convenient and reproducible method,...

The quantification of water use of citrus orchards is important in order to prevent stress developing in the orchard and to avoid wasting precious water resources. Measurement of citrus orchard water use is not possible under all environmental and management combinations because of the expense and time it takes to make the measurements. Models whic...

Losses in the production of avocado (Persea americana (Mill.)) are incurred due to Phytophthora root rot (PRR), a disease of the feeder roots that results in tree-dieback and eventual tree death. Avocado is also a flood-sensitive species and flooding exacerbates the effects of PRR. The avocado industry relies on the use of rootstocks tolerant to PR...

Heat pulse velocity sap flow measurement techniques are considered reliable and accurate for estimating tree water use in woody species. In order to be representative and scalable, probes are typically installed in a number of sample trees and inserted to stratified depths to account for heterogeneity in hydraulic conductivity exhibited by the sapw...

This study was done to identify random amplified polymorphic DNA (RAPD) markers that may associate with seven important traits in tea. Sixty RAPD primers were first screened using 18 cultivars under each of the 7 traits, followed by confirmatory screening of 20 promising primers with 32 tea cultivars. Six RAPD primers generated a total of nine spec...

The determination of accurate figures for orchard water use is critical for improved irrigation scheduling and for the issuing of water licenses. Under- or overestimations can have serious implications for production and water resources in water scarce countries, such as South Africa. In order to meet this need for more definite water use figures t...

Labour costs and shortages and cost of production has resulted in the tea industries in central and southern Africa becoming unprofitable. This has led to the full mechanization of shoot harvesting by using hand-held and ride-on machines. However, it is evident that yield has declined with mechanical harvesting. Under mechanical harvesting, due to...

The water use of ‘Cripps Pink’ apples and ‘Delta’ Valencia oranges was estimated for different seasons in 2008 and 2009. Heat pulse velocity (HPV) systems were used to monitor sap flow rates from the apple and orange trees. Total evaporation was estimated using the surface renewal (SR) and eddy covariance (EC) methods. Total evaporation and transpi...

Final fruit size is the consequence of complex metabolic events that occur between fruit set and maturation. Disruption of these biochemical and molecular processes at any stage during fruit growth will impact on final fruit size. Because fruit size is a function of cell number rather than cell size, factors affecting cell division cycle activity a...

Endogenous embryo factors, which act mainly in the radicle, prevent germination in Tagetes minuta at high temperatures. These factors act to prevent cell elongation, which is critical for radicle protrusion under optimal conditions. Once the radicle has emerged both cell elongation and cell division are required for post-germination growth. Germina...

An investigation into the role of carbohydrates in flowering of the endangered species Kniphofia leucocephala Baijnath. (Asphodelaceae) in vitro revealed that a carbohydrate source is essential for the induction of inflorescences. Both the concentration and type of sugar influenced the percentage of flowering, with 60gl−1 fructose and 10μM N6-benzy...

Thermoinhibition in Tagetes minuta achenes is tightly and rapidly regulated with regard to its imposition and release, with both processes occurring within 2-3h. Germination at high temperatures is almost exclusively regulated by the embryo, while the pericarp appears to play only a minor role. Thermoinhibition in T. minuta could not be alleviated...

The role of cytokinins in the promotion of flowering in the endangered species Kniphofia leucocephala Baijnath. was investigated using shoots maintained in culture for 3 years. The highest percentage flowering (65%) was obtained on media containing 20 mu M benzyladenine (BA). The inclusion of isopentenyladenine and zeatin in the media also resulted...

Plant hormones play an important regulatory role in growth and development of fleshy fruits and often these are synthesized in a sequence that is tissue- and/or fruit-specific. Previous studies using Hass avocado and its small-fruit phenotype as a model demonstrated a relationship between the cytokinin/abscisic acid ration and final fruit size. Mor...

The contribution of xanthine dehydrogenase (XDH, EC 1.1.1.204) to fruit size was investigated using the normal and small-fruit variants of Persea americana Mill. cv. 'Hass'. Inhibition of XDH by treatment of normal fruit, in the linear phase of growth (phase II), with allopurinol (Allo) arrested fruit growth. Adenine (Ade), a less effective inhibit...

Although 40 years have passed since the first discovery of a naturally occurring cytokinin (CK) in plants, the biosynthetic pathway still remains unresolved. Numerous factors have contributed to the lack of success in this area, but most alarming has been the reliance upon unproven hypotheses and preconceived ideas. The greatest obstacle has been t...

Control of plant hormone homeostasis is crucial for normal organdevelopment in plants. To elucidate the contribution of plant hormonehomeostasis to fruit growth, tissue distribution and activity of xanthinedehydrogenase (XDH), abscisic aldehyde (AB-ald)- and indole acetaldehyde(IA-ald) oxidase, and cytokinin oxidase (CKOX) were determined in seed,...

The sucrose non-fermenting-1-related protein kinase (SnRK1) complex is considered to play a central role in sugar sensing and signalling in growth and development of plants/plant parts. This paper reviews the SnRK1 complex and its role in the regulation of key metabolic pathways contributing to cell growth and development. Based on results from stu...

Avocado fruit growth is the result of sustained cell division and cell expansion. Studies have revealed that cell division is the limiting factor in the control of fruit growth and that the endogenous cytokinin to auxin to abscisic acid ratio is critical in supporting continued fruit growth. Detailed biochemical studies have led to the proposal tha...

Avocado trees are extremely sensitive to both soil-flooding and the root rot caused by Phytophthora cinnamomi. It is well known that flooding exacerbates the effects of Phytophthora root rot (PRR), causing significant damage that leads to devastating losses worldwide. Early symptoms of plant stress often include decreases in stomatal conductance (g...