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Yu-Sen Chang and Chen-Yu Lin

The effect of copper hydroxide [Cu(OH)2] applied to interior container surfaces on shoot and root responses was evaluated on palimara alstonia (Alstonia scholaris). The seedlings grown in Cu(OH)2-treated containers had greater plant height than those in untreated containers, and had no observable copper toxicity symptoms. Cu(OH)2-treated containers effectively reduced root circling on the surface of rootballs compared with untreated containers. The Cu(OH)2 treatment significantly increased the dry weight of fine roots (those with a diameter 0-2 mm) and small roots (>2-5 mm) but did not influence the dry weight of medium roots (>5-10 mm), large roots (>10 mm), or total roots. The Cu(OH)2 treatment also significantly increased total root length and surface, which was due principally to the increasing length and surface of the fine roots. The results indicated that the Cu(OH)2 treatment, which can improve the root quality of palimara alstonia seedlings and thereby increase the root-length-to-leaf-area ratio and the root-surface-to-leaf-area ratio, has the potential to produce high-quality plants.

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Wan-Wei Yu, Der-Lin Ling, and Yu-Sen Chang

Research on the restorative benefits of nature primarily has focused on the spiritual benefits of wilderness areas, but other areas, such as cities, have not been studied. Horticultural activities have the potential to promote spiritual health, but most participants are not aware of this benefit. To improve this situation and to increase evidence of the benefits of therapeutic horticulture, this study suggests treating plant parables as trigger cues, which would allow an approach to interaction with plants through metaphysical imagination, resulting in an improvement in spiritual health from horticultural activities. The purpose of this study was to understand participants' beliefs of the spiritual benefits of horticultural activities, and to see if these beliefs were enhanced after reading plant parables. This study surveyed subjects with different horticultural backgrounds, and measured their opinions regarding belief in the spiritual benefits of horticultural activities, before and after reading the parables. The results indicated that before reading the plant parables, neither group of subjects with different horticultural backgrounds agreed with the spiritual benefits of horticultural activities; however, after reading the plant parables, the belief of participants with formal horticultural education backgrounds increased significantly (P ≤ 0.001). The increase was not significant in subjects without formal horticultural education backgrounds.

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Kuan-Hung Lin, Shao-Bo Huang, Chun-Wei Wu, and Yu-Sen Chang

Exogenous application of either salicylic acid (SA) or calcium chloride (CaCl2) to alleviate heat stress has been extensively studied. However, the effects of combined SA and CaCl2 treatment on the heat tolerance of poinsettia have been poorly studied. This study investigated the role of a foliar spray comprising SA and CaCl2 in managing heat tolerance of three poinsettia (Euphorbia pulcherrima Willd.) cultivars, Noel, Winter Rose (WR), and Ice Punch’ (IP). Plants were pretreated with SA, CaCl2, or combined SA and CaCl2 and then exposed to a temperature of 42 °C for 1 hour. Changes in the relative injury (RI) percentage, malondialdehyde (MDA) content, and antioxidant enzyme activities were determined. All plants were then placed in an environment-controlled greenhouse for 14 days and evaluated. Lateral bud sprouting (%), new leaf numbers, and phenotypic appearance were recorded. Results revealed that the three poinsettia cultivars varied in their appearance, morphological growth patterns, and ability to tolerate high-temperature stress. Plant growth of ‘Noel’ was more robust than that of ‘WR’ and ‘IP’, which were considerably affected by heat stress, resulting in brown, withered leaves and defoliation. In general, the effects of the combined application of SA and CaCl2 on heat-tolerant ‘Noel’ were superior to those of individual applications and no treatment (for control groups) in terms of the RI percentage, lateral bud sprouting (%), and appearance under heat stress. Application of combined SA and CaCl2 for ‘Noel’ plants was more beneficial for enhancing catalase activity and resulted in the effective alleviation of decreased malondialdehyde content under heat stress. Treatment including 200 μΜ SA and 10 mm CaCl2 may alleviate heat stress and may prove useful in breeding programs focused on improving poinsettia cultivars.

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Yung-Liang Peng, Fang-Yin Liu, Rong-Show Shen, and Yu-Sen Chang

Nitrogen (N) is a major element required for crop cultivation and an important factor affecting plant growth and development. Malabar chestnut (Pachira macrocarpa) is an important ornamental potted plant crop whose N requirement has been studied, and a rapid monitoring method to manage N fertilization during its commercial production is yet to be established. Malabar chestnut seedlings were fertilized weekly with 0, 4, 8, 16, or 24 mm N. After 12 weeks, 16 mm N was found to yield the greatest plant growth such as plant height, number of nodes, and total leaf area. Measurements of chlorophyll meter readings, leaf chlorophyll concentration, leaf N concentration, and leaf dry weight all indicated that the optimal level of N fertilization was 16 mm N. A chlorophyll meter can be used to monitor nondestructively whether sufficient N has been supplied to support optimal plant growth. In this study, a chlorophyll meter reading of 46.1 corresponded with a critical leaf N concentration of 2.65%, defined as the leaf N concentration when the leaf dry weight was at 90% of saturation point. Additional N supplied beyond this critical level increased foliar chlorophyll content and improved the rate of net photosynthesis. Therefore, chlorophyll meter readings, which are convenient and nondestructive can serve as a reliable reference for commercial production in monitoring N requirement for optimum growth of malabar chestnut. Weekly fertilization of malabar chestnut with 16 mm N and maintaining leaf chlorophyll meter readings between 46.1 and 58.4 are recommended.

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Furn-Wei Lin, Kuan-Hung Lin, Chun-Wei Wu, Yu-Sen Chang, Kuan-Hung Lin, and Chun-Wei Wu

Plant biostimulants have received increasing attention in recent years because of their positive effects on crop performance and contribution to agro-ecological sustainability. The aim of this study was to determine the influence of betaine and chitin treatments, alone and in combination, on lettuce plants by changes in the morphology and physiology of plants exposed to regulated deficit irrigation (RDI). Plants were subjected to full irrigation (FI; no water deficiency treatment, field capacity >70%) and RDI (field capacity <50%) conditions until the end of each experiment. We recorded plant yield–related traits, net photosynthesis, and water use efficiency (WUE) values weekly for 4 weeks and carried out three individual experiments to assess the efficacy of biostimulant and irrigation treatments. Betaine (0, 50, and 100 mm/plant) was foliar-treated every 2 weeks during Expt. 1, whereas chitin (0, 2, and 4 g/kg) was applied to the soil at the beginning of Expt. 2. We then applied the optimal concentration of each chemical alone or in combination to the plants as Expt. 3. Compared with negative control, the application of 50 mm betaine and 2 g/kg chitin significantly increased leaf area (LA) per plant by 48.5% and 25.6%, respectively. Furthermore, 50 mm betaine and 2 g/kg chitin treatment showed a clearly protective effect in RDI plants, enhancing their total fresh weights by 26.10% and 75.0%, respectively, in comparison with control. Comparing WUEyield and WUEbiomass, chemical-treated plants had higher values than control. Betaine (50 mm) or chitin (2 g/kg) treatments alone significantly elevated LA, fresh shoot weight, total fresh and dry weights, net photosynthesis, and WUE values, and boosted the water stress tolerance of lettuce under RDI compared with controls. However, a combined treatment of 50 mm betaine and 2 g/kg chitin did not increase the levels of all yield traits under RDI compared with individual chemical treatment. Most leaves appeared healthy, green, and had visually less leaf chlorosis when treated with chitin or betaine under RDI compared with untreated plants subjected to RDI. Our study indicates that applying betaine and chitin improves plant performance against water supply limitations and highlights their potential for the sustainable production of lettuce.