Kuo-Tan Li

Summer pruning reduces whole-canopy carbon fixation and transpiration in apple trees

Summary Canopy size control is one of the major purposes of summer pruning. However, reducing canopy size might also result in less light interception, consequently decreasing canopy photosynthetic efficiency and carbohydrate production, which might lead to the imbalance of carbohydrate supply and fruit demand. To document the effectiveness of summer pruning on canopy control and the impact on canopy gas exchange, pruning treatments at four levels of intensity (unpruned, light, moderate, and severe) were carried out on mature ‘Empire’/M.9 slender spindle apple trees (Malus domestica Borkh.) on 30 July 1998 and 4 August 1999. Changes in canopy leaf area after summer pruning were estimated. Canopy net carbon exchange rate (NCER) and canopy transpiration before and after summer pruning were monitored. Canopy growth was suppressed by summer pruning and the post-pruning regrowth was insignificant. Canopy NCER was reduced in proportion to the amount of leaf area removed by summer pruning. The result suggests that commercial pruning intensity similar to the moderate to severe treatments in this study could cause a significant reduction in canopy NCER and carbohydrate production. In addition, canopy transpiration was reduced in proportion to pruning intensity. Lower water consumption and improved water status during the growing season after summer pruning might benefit fruit growth and relieve the potential detriment due to carbohydrate shortage.

Summer pruning effects on fruit size, fruit quality, return bloom and fine root survival in apple trees

Summary While many undesirable effects of summer pruning on apple (Malus domestica Borkh.) growth and development have been reported, the results are inconsistent and difficult to interpret. This study resolves the inconsistency by supplying a model that integrates pruning effects with tree physiological crop load, i.e. canopy net carbohydrate exchange rate per fruit. Our previous study suggests that the potential impact of reducing canopy photosynthesis after summer pruning depends on the balance of carbohydrate supply and demand. To test the hypothesis that summer pruning affects carbohydrate balance, we measured fruit growth, fruit quality, return bloom, and root growth in 20 year old slender spindle ‘Empire’/M.9 apple trees in response to different severities of summer pruning. Results were interpreted in relation to pruning severity, fruit number per tree, and the physiological crop load. Within commercial cropping ranges, light and moderate summer pruning had slight influences on fruit size and fresh weight. Summer pruning did not affect fruit colour, soluble solids content, starch, firmness, and internal breakdown after storage. Summer pruning alone did not affect return bloom or root growth. However, the potential negative effects of summer pruning on fruit growth, return bloom, and fine root survival can be predicted through their relationships with physiological crop load. This study suggests that the carbohydrate supply and demand balance model feasibly explains summer pruning influences. In addition, the impact of carbohydrate shortage after summer pruning is likely to be mediated by the reduction in canopy transpiration. However, the interaction between canopy carbon balance and water status after summer pruning is also likely to be manipulated by annual weather pattern.

Girdling improved berry coloration in summer but suppressed return growth in the following spring in 'Kyoho' grapevines cultivated in the subtropical double cropping system

Plenary lecture given at the 8th Mid-European Clay Conference, held in Kosice (Slovakia) on July 4-8th, 2016.COST MOLIM WG3 Meeting, Algorithm Development and High-performance Computing in Chemistry and Physics; Bratislava, March 21-22, 2016; http://web4.umb.sk/molim2016/Oral presentation given at the 8th Mid-European Clay Conference, held in Kosice (Slovakia) on July 4-8th, 2016. S6: application and treatment of clays and other industrial minerals.Cost Action Molim, Molecules in Motions, CM 1405; University Paris-Est Marne-La-Vallee, France, 27-29 August 2015This chapter provides an overview of the main biochemical transformations of major elements, including carbon, nitrogen, sulfur, iron and phosphorus in anaerobic digesters. Mineralization of organic matter during anaerobic digestion processes results in the production of inorganic carbonate, ammonium, sulfide, and phosphate species, which are involved in a complex network of chemical and biological reactions through interaction with available macro and micro nutrients as well as microbial processes with profound effects on the efficiency and stability of the anaerobic digester performance. The interplay of iron, phosphorus and sulfur cycles has recently attracted attention in the frame of research developed for the recovery of phosphorus on one hand and in the frame of the

Differential responses to short-term salinity stress of heat-tolerant cherry tomato cultivars grown at high temperatures

Although many new tomato cultivars with various degrees of heat-tolerance have been released, year-round tomato production in subtropical lowlands is still challenged by summer heat and an increasing risk from salinity stress. Little information about the simultaneous effects of heat and salinity on growth and fruiting in tomatoes is available. It was hypothesized that cultivars which perform better in high temperatures are also more tolerant to salinity stress. Two highly heat-tolerant cultivars, ‘Tainan ASVEG No. 19’ (TA19) and ‘Taiwan Seed ASVEG No. 22’ (TSA22), and one moderately heat-tolerant cultivar, ‘Hualien ASVEG No. 21’ (HA21), were grown under high temperature conditions and were irrigated with a 0, 50, 150, or 200 mM NaCl solution for 20 days. Vegetative growth, fruiting behavior, and fruit quality were monitored. Number of leaves, leaf area, shoot fresh and dry weights, and root fresh weight were generally decreased with increasing level of salinity stress, but root dry weight was not affected, resulting in an increase in root to shoot ratio in all three cultivars. Yield was also decreased by salinity treatments in all three cultivars due to reduced number of flowers, fruit set, and fruit size. The highly heat-tolerant ‘TA19’ had the lowest vegetative growth and the highest yield under the high temperature condition, but the yield was strongly suppressed by the short-term mild salinity treatment. On the other hand, vegetative growth was little affected and the degree of yield reduction was less intense with the short-term mild salinity treatment in the moderately heat-tolerant ‘HA21’. The result indicated that effects of heat stress and salinity stress are not additive and differential responses to salinity under high temperatures exist among cultivars with various degrees of heat-tolerance.

Dormant season fertigation promotes photosynthesis, growth, and flowering of ‘Blueshower’ rabbiteye blueberry in warm climates

In the subtropical lowland of Taiwan with a warm winter climate, most rabbiteye blueberry cultivars (Vaccinium ashei) are semi-deciduous, and their leaves remain green through the winter. We investigated whether fertigation with nitrogen (N) and phosphorus (P) during the dormant season had any subsequent effects on vegetative growth and flowering of rabbiteye blueberry in this region. Potted 3-year-old ‘Blueshower’ plants were fertigated weekly from November 2012 to March 2013 with combinations of 100, 200, or 400 mg·L-1 N and 200 or 400 mg·L-1 P. Plants fertigated without N and P served as the control. Fertigation with any N and P treatment during the dormant season significantly increased photosynthesis (Pn) of overwintered leaves relative to the control, but had no effect on Pn of the new leaves. N at 100 mg·L-1 increased the total chlorophyll content in overwintered leaves more than two-fold compared to the control; total chlorophyll content in overwintered leaves increased with N rate, but was not affected by P rate. Dormant-season N and P fertigation advanced vegetative budburst. However, new shoot growth was negatively affected by dormant-season P fertigation. The number of flowers increased with N rate. We concluded that in the subtropical lowland with a warm winter climate, dormant-season fertigations, especially to supply N, can improve flowering and canopy development in the following spring.

Partial defoliation and runner removal affect runnering, fruiting, leaf photosynthesis and root growth in ‘Toyonoka’ strawberries for subtropical winter production

Removing runners and old leaves are two major routine and labor consuming tasks in winter strawberry (Fragaria × {ptananassa} Duch.) production in subtropics. However, the potential negative effects of defoliation has not been evaluated. We studied the effects of partial defoliation and runner removal on plant growth, leaf photosynthesis (Pn), and yield in field-grown or potted strawberry plants (‘Toyonoka’). The treatments were consisted of partial defoliation by removing leaves older than 45 days (PD), removing all runners (DR), PD + DR, and the control (CK). Treatments were applied weekly from mid-November until early March. DR promoted yield and number of fruits for the first harvest cycle but not for the second harvest cycle. Multiple linear regressions indicated that leaf area had greater overall effects on runnering and fruit traits than the existence of runners. The leaf Pn was not responsive to DR but a transient increase in Pn was consistently detected on the remaining leaf after each PD treatment. The compensatory increase in Pn was only detectable within 1 days after each PD treatment, indicating that the actual compensation for partial loss of functioning leaf area may be negligible. Crown dry weight was less affected by canopy manipulation than growth and dry weight of roots. Our results indicated that yield of strawberry in Taiwan’s subtropical climate can be improved by removing runners while maintaining a greater leaf area with less severe defoliation.