Sucrose metabolism in watermelon fruit is affected by fruit-setting method under plastic film greenhouses

Fruit set represents the very first step of fruit development. This study investigated the effect of different fruit-setting methods [1-(2-chloro-4-pyridyl)-3-phenylurea (CPPU) treatment, artificial pollination, and honey bee pollination] on the concentrations of fructose, glucose, and sucrose, and the activities of sucrose metabolising enzymes of watermelon fruit under plastic film greenhouse conditions. No significant difference in fructose and glucose concentrations was observed among the three treatments at fully ripe stage of fruit [33 days after anthesis (33 DAA)]. However, artificial and honey bee pollination significantly increased sucrose concentration. Measurement of sucrose metabolising enzyme activities and correlation analysis demonstrated that the increased activity of SuSy-s (sucrose synthase, synthesis direction) is the key mechanism of increased sucrose concentration in the artificially pollinated and honey bee pollinated fruits. The concentrations of fructose, glucose, and sucrose were similar between artificially pollinated and honey bee-pollinated fruits at fully ripe stage (33 DAA). Therefore, we can conclude that artificial and bee pollination can improve the sweetness of watermelon fruit. In addition, the honey bee can provide a pollination service that is similar to that of artificial pollination for watermelon grown in a protected cultivation system.     

柑桔授粉处理和单性结实子房（幼果）内源IAA,ABA和ZT含量的变化

广橙在授粉后３天内即完成受精，与未授粉子房相比，授粉子房迅速膨大，授粉处理可使内源ＩＡＡ、ＡＢＡ和ＺＴ水平急剧上升，尤其是在处理后的前３天。至第４天趋平缓。以每子房ｎｇ含量计，至处理后第３天，ＩＡＡ、ＡＢＡ和ＺＴ含量分别是处理开始时的６．８、５．２和４．１倍，而未授粉的分别为２．５、２．６和１．２倍，这种变化与子房（幼果）的发育密切相关。试验还分析了广橙授粉处理与内源激素平衡关系，发现授粉处理ＡＢ     

Influence of pollination methods on fruit development and sugar contents of oriental melon (Cucumis melo L. cv. Sagyejeol-Ggul)

This study was conducted at the Seongju Fruit Vegetable Experiment Station for 2 years, 2002–2003 to investigate the effect of pollination methods on development and sugar content of oriental melon fruits. Oriental melon fruit was pollinated by honeybees (Apis indica) and bumblebees (Bombus ignitus) and fruit setting growth regulators was used as a control treatment. Fruits pollinated by honeybees and bumblebees has lesser length and width of fruit compared to the control. Pollinated by bumblebees increased hardness and soluble solids of fruits by 27% and 4–5% and that of honeybees increased hardness and soluble solids of fruits by 12% and 5–10% compared to the control, respectively. Fermented fruit ratio (%) of oriental melon fruit pollinated by honeybees, bumblebees, and growth regulator was 6.7%, 9.1%, and 28.1%, respectively. Glucose, fructose and sucrose contents of fruits by HPLC (high performance liquid chromatography) were very low throughout the ripening stage, but abruptly increased at harvesting stage. In fructose content of fruits, pollination of bumblebees and honeybees was higher by 9% and by 13% than those of control, respectively. The amount of total sugar content in fully ripen fruits of oriental melon was not different between the treatments (P > 0.05). Total sugar content (%) of fruits pollinated by bumblebees was slowly decreased until 15 days after storage compared to that of other treatment. For the low fermented fruit ratio (%) and slowly reduced total sugar content at storage of fruits, the pollination of bees was more useful than fruit setting growth regulators in early cultivation of oriental melon under plastic houses. The economic analysis according to the pollination method will be needed in the near future.     

Fruit set and embryo rescue in crosses using parthenocarpic ‘Mopanshi’ persimmon

The ‘Mopanshi’ persimmon is a seedless, astringent parthenocarpic cultivar that does not produce male flowers. After pollination using four non-astringent cultivars (‘Zenjimaru’, ‘Nishimurawase’, ‘Okugosho’ and ‘Hanagosho’), seeds were produced to different degrees. ‘Mopanshi’ fruits pollinated with ‘Zenjimaru’ produced far more seeds than those pollinated with the other three cultivars. The ratio of abnormal seeds obtained from the fruits pollinated with ‘Hanagosho’ was higher than that obtained from the fruits pollinated with the other three cultivars. Most embryos degenerated in the early to late stages of seed development. Immature embryos were cultured in a modified MS medium (half of NO₃ in MS medium + 0.4 μM BA + 0.1 μM IBA) with the greatest success (52–80%) from embryos taken from fruits 60–80 days after pollination. Seedlings failed to initiate radicles so they were transferred to dark culture conditions for 8 days or to a rooting media that contained 3% sucrose and 1% Chinese ink. The seedlings on the medium darkened with ink rooted at greater than 90.83% compared to 75.83% for dark cultured seedlings. This study demonstrated that ‘Mopanshi’ persimmon could be used as a female parent in crosses, but embryos needed to be moved to tissue culture conditions to continue to develop and form plantlets.     

Consequences to fertilization of the developmental stage of apricot ovules at anthesis

Summary

Flowers at anthesis from the apricot cvs Palstein and Goldrich were examined to determine their ovule maturity stage. Further, flowers from both cultivars were pollinated and collected after 2000 and 3000 growing degree hours (GDH) in two consecutive years. Numbers of fertilized ovules were recorded in those flowers. Ovules of ‘Palstein’ from flowers at anthesis showed predominantly an embryo sac at the eight nuclei stage of development while embryo sacs in ‘Goldrich’ were mainly in a four nuclei stage. After 2000 GDH from pollination 90% of viable ovules were fertilized in ‘Palstein’ whereas only 37.5% of them were fertilized in ‘Goldrich’. After 3000 GDH, Goldrich presented the same percentage of fertilized ovules that was recorded after 2000 GDH. Non-fertilized ovules did not degenerate and developed normally in pollinated and non-pollinated flowers from both cultivars. Further, non-fertilized pollinated flowers were not different from non-pollinated flowers in the development of the embryo sac, indicating that the chances for fertilization would not be increased by pollination in apricot. We suggest that the lack of fertilization in ‘Goldrich’ is due to degeneration of the male gametophyte, which would have a limited life, not long enough for the embryo sacs to develop to maturity.     

Influence of harvest time and after-ripening on the seed quality of eggplant

Eggplant cv. Emi and Tsakoniki were cultivated for seed in an unheated greenhouse and fruits were harvested at 25–65 days after anthesis (DAA) in order to determine the optimum harvest time. In addition, the effect of after-ripening on seed quality (i.e. seed size and germination) was examined by storing harvested fruit at 25 °C for 20 days prior to seed extraction. From the results, it was concluded that the optimum time of harvest for seed production is 55 DAA. Seeds extracted from fruits that were harvested at 25–35 DAA did not germinate, but when fruits harvested at the same age were stored for 20 days at 25 °C prior to seed extraction (i.e. seeds were after-ripened) germination was induced. Seeds extracted from fruits harvested at 45 DAA showed a high percent germination, which decreased after storage at 25 °C for 3 months. This decrease, however, was reduced by after-ripening prior to extraction. It is concluded that although eggplant is a non-climacteric species and fruit do not ripen after harvest, nevertheless seeds within the fruit continue to fill and mature after harvest; hence storage of prematurely harvested fruit prior to seed extraction permits the seeds of these fruits to after-ripen in situ and thereby increases seed size and germination. The implication of this result for eggplant seed production is discussed.     

Early cell enlargement by night-time heating of fruit produce watermelon fruit (Citrullus lanatus Matsum. et Nakai) with high sucrose content

To investigate the effects of night-time temperature on cell and fruit size, and sugar accumulation in watermelon fruit, fruits were treated with high night-time temperatures in a greenhouse. The minimum night-time ambient temperature of the heating box (18 °C) was approximately 6 °C higher than that of the control. The length, diameter and weight of heat-treated fruit at the end of heating treatment, 16 days after anthesis (DAA), were significantly greater than that of control fruit, but those at harvesting, 42 DAA, were almost the same in both treatments. Mean cell size of the outer portion of heat-treated fruit at 16 DAA was significantly larger than that of the control. Cell size of the fruits at 42 DAA did not differ between heat-treated and control fruits. Sucrose, glucose and fructose content of fruit at 16 DAA did not differ between heat-treated and control fruit. However, sucrose content of the outer portion of heat-treated fruit was 162% of that of control fruit at 42 DAA. Glucose and fructose contents at 42 DAA did not differ between heat-treated and control fruit, except glucose content of outer portion.     

果梅花不同发育阶段花粉原位萌发及花粉管生长特性

为探明自花、异花花粉在果梅花的不同发育阶段原位萌发及生长的特性,以细叶青果梅为材料,取开花前6、4、2d、开花当天和花后2d的花(花蕾),分别于自花、异花授粉(莺宿)后12、24、48、72、96h切取花柱,用FAA固定液处理,荧光染色后压片观察。结果表明,自花花粉在柱头上的萌发率略低于异花(开花前4d存在显著差异),开花前6、4d极显著低于其他各阶段,花蕾越幼小花粉萌发越差,开花当天花粉萌发率超过80%;开花前4d之前的花柱内异花花粉管数量显著低于开花前2d及之后各期的,果梅开花前4d以前的花发育不充分;开花后2d生长到花柱基部的异花花粉管数量较多,属于有效授粉期。果梅在开花前4d开始具备抑制自花花粉管生长的能力,并且随着花的发育逐渐增强,开花当天最强,开花后开始减弱。果梅自交授粉期以开花前2～3d为宜。     

Effect of pistil age and pollen parent on pollen tube growth and fruit production of pistachio

Female pistachio (Pistacia vera) trees were hand pollinated with pollen from three different male genotypes 0,1,2,3 and 4 d after anthesis. Results were measured by mature fruit set and by fluorescence microscopy of pollen germination and tube growth in the pistil. Maximum pollen tube growth and fruit set of split nuts was achieved following pollination within two days of anthesis. Three day old pistils supported pollen tube growth, but fruit set was low. Four day old pistils supported little pollen tube growth or fruit set. Significant differences were also apparent between pollen parents, with low pollen tube growth and fruit set following interspecific pollination with P. atlantica pollen. All pollen tubes were observed to penetrate chalazogamously, and parthenocarpic production of blank fruits occurred in both unpollinated and pollinated treatments. The results indicate that for optimum fruit production of pistachio, pollen transfer must be achieved within 2 d of anthesis and pollination by P. atlantica should be avoided.     

Sensitive stages of fruit and seed development of chili pepper (Capsicum annuum L. var. Shishito) exposed to high-temperature stress

The sensitivity of developmental stages to high temperature was investigated in chili pepper (Capsicum annuum L. var. Shishito). Plants were subjected to heat stress (38/30 °C day/night) immediately after anthesis for 5 or 10 days, or from 10 to 30 days after anthesis (DAA), from 30 DAA until harvest of the seeds, or immediately after anthesis until harvest of the seeds. Control plants were grown at 30/22 °C (day/night). Exposure to high temperature (heat stress) during different periods of development after anthesis adversely affected fruit growth, seed yield, and seed quality in chili pepper. Heat stress for the whole period after anthesis, and from 30 DAA until harvest reduced the growth period of chili fruits by 15 and 10 days, respectively. Heat stress from 10 to 30 DAA reduced fruit width and fruit weight. The early stage of seed development from anthesis until 10 DAA was sensitive to high temperature, which affected fruit length, fruit weight and seed set. Applying high temperatures to plants for 10 DAA increased the proportion of abnormal seeds per fruit. High temperatures from 10 DAA until 30 DAA inhibited carbohydrate accumulation and adversely affected seed germinability and vigor. These results suggest that the stage of development at which chili peppers are exposed to high temperatures is an important factor in fruit and seed growth and in seed quality.     

Effects of high electrical conductivity of nutrient solution and its application timing on lycopene,chlorophyll and sugar concentrations of hydroponic tomatoes during ripening

Tomato (cv. Durinta) plants were grown hydroponically under two electrical conductivities (EC, 2.3 and 4.5 dS m⁻¹) of nutrient solution inside a greenhouse. The high EC treatment was initiated either immediately after anthesis (high EC treatment) or 4 weeks after anthesis (delayed high EC treatment). Fruits were harvested weekly beginning 2 weeks after anthesis, until all fruits reached the red stage (8 weeks after anthesis). Lycopene, chlorophyll, sugar and total soluble solid (TSS) concentrations of fruits were measured every week for all harvested tomatoes from the different ripeness stages. The results showed that lycopene concentration, fructose and glucose concentrations and TSS of red ripe tomato fruits were enhanced by both high EC and delayed high EC treatments compared to those in the low EC treatment. The lycopene concentration of red ripe tomato fruits in the high EC and the delayed high EC treatments showed an increase of 30–40% (1.29–1.39 mg g⁻¹ dry matter) compared to those in the low EC treatment (0.99 mg g⁻¹); however, there was no significant difference in the lycopene concentration between the high EC and delayed high EC treatments. TSS of red ripe tomato fruits grown in the high EC treatment was 6.1%, significantly greater than those grown in the delayed high EC treatment (5.7%). Weekly change in lycopene concentration indicated that lycopene synthesis was enhanced by the high EC treatment, regardless of the application timing. Regardless of EC treatment, chlorophyll concentration in fruit declined linearly during fruit development and ripening and reached non-detectable levels 7 weeks after anthesis. Our results indicated that: (1) accumulation of sugars and TSS in fruit was due to reduced water flux to the fruit under high EC as previously reported, and (2) lycopene synthesis was promoted by, but chlorophyll degradation was independent from, the osmotic and/or salt stress caused by the high EC.     

Pollination behaviour of Nardostachys jatamansi DC., an endangered medicinal and aromatic herb

Nardostachys jatamansi is a perennial, endangered medicinal and aromatic herb of family Valerianaceae, distributed in subalpine to alpine areas. Being an endangered species it should be conserved through in situ as well as ex situ methods. Study of reproductive biology is necessary for effective conservation of endangered plants and pollination behaviour is an integral part of reproductive biology. Present study deals with pollination behaviour of N. jatamansi. Parthenocarpy, passive autogamy, active autogamy, geitonogamy and xenogamy experiments were applied in this study. Flowering (peak) takes place during the month of July–August and anthesis between 7:00–11:00 h. Anthers disperse pollen grains after 24 h of anthesis. Stigma is of protogynous type. Fruit set recorded in above experiments was 40% in passive autogamy, 70% in active autogamy, 53.33% in xenogamy and 86.67% in geitonogamy as well as open pollination experiments. The species is self-pollinated but dependent on pollinators for optimum pollination. Cross pollination may have adaptive value for species as it compensate failure of autogamy and also maintains genetic variability in the population. Crop improvement program may be initiated through xenogamy.     

不同发育阶段甜樱桃花授粉后花粉萌发和花粉管生长的差异

选用自交不亲和性程度不同的2个甜樱桃品种莫利和拉宾斯为试材,分别在开花前、开花当天和开花后进行莫利自花、拉宾斯自花和莫利×拉宾斯异花授粉,并于授粉后12、24、48、72、96h切取花柱,用FAA固定,荧光染色后压片观察。结果表明,3个组合的花粉萌发率都以开花当天授粉的最佳,拉宾斯自交和莫利×拉宾斯的花粉管生长状况也以开花当天授粉的最佳,但莫利自交的花粉管生长状况却以花前第4天最佳,花后第4天次之,而当天授粉的最差。因此认为,甜樱桃自交不亲和程度与其雌蕊的发育状态密切相关,蕾期授粉和延迟授粉都能够在一定程度上克服甜樱桃的自交不亲和性,但蕾期授粉的作用更加明显。     

Effect of propagation material on some quality attributes of strawberry fruit (Fragaria x ananassa, var. Selva)

In the Mediterranean region, cold-stored plants (summer planting system) are used as the main strawberry planting material (plant establishing period July–August). However, recently fresh plants (winter planting system) have also started being used for strawberry production (plant establishing period October–November). As the plantations originated from cold-stored or fresh plants differ in plant growth and yield, some differences in fruit quality have also been expected; therefore, the objective of the current study was to compare fruit quality of plants originated from different propagation material. Cold-stored plants were well developed before the beginning of the spring harvest, while fresh plants continued growth concomitantly with fruiting. The harvesting period of cold-stored plants lasted 4–6 weeks (second week of April–second half of May). Fresh plants produced fewer and larger fruits than cold-stored plants, but for a longer harvest period, which lasted throughout all summer. Differences in soluble solids and dry matter content between the fruits from cold-stored and fresh plants were observed in the first three sampling dates in both years of the experiment. In some sampling dates, significant differences in anthocyanin, titratable acidity and ascorbic acid content, were observed between fruits of plants originated from different propagation material.     

In vitro shoot multiplication and plant regeneration in four Capsicum species using thidiazuron

A procedure of in vitro plant propagation using shoot meristem explants (∼0.5 cm) has been developed for Capsicum annuum cv CA960, C. baccatum, C. frutescens and C. praetermissum on Murashige and Skoog [Murashige, T., Skoog, F., 1962. A revised medium for rapid growth and bioassays with tobacco tissue cultures. Plant Physiol. 15, 473–497] medium containing various cytokinins. Among various concentrations of cytokinins tested; adenine (Ad), N⁶-benzyladenine (BA), kinetin (Kn), zeatin and thidiazuron (TDZ) individually. TDZ regenerated maximum number (4.2–22.4) of shoots in all the Capsicum species tested. Multiple shoot elongation occurred upon transfer to BA (0.22 μM l⁻¹) + IAA (0.48 μM l⁻¹). Rooting of regenerated shoots was achieved on medium supplemented with 5.71 μM l⁻¹ indole-acetic acid (IAA). Rooting was observed in 72–94% of shoots obtained from TDZ-containing regeneration medium followed by elongation treatment in contrast to 8–22% of shoots without elongation treatment. Plantlets obtained from TDZ-containing media were normal diploid (2n = 24) and could readily be established in the soil under green house conditions with a survival frequency of 68–84%. Regenerated plants were developed into morphologically normal, fertile plants and able to set viable seeds.     

Effective pollination period in durian (Durio zibethinus Murr.) and the factors regulating it

The effective pollination period (EPP) of durian was determined by both delayed and bud pollination, during which reproductive factors affecting the EPP, e.g., stigma receptivity, pollen tube growth in the style, and ovule longevity were studied histologically. This study was conducted in three distinct locations in Thailand, namely, the Chantaburi Horticultural Research Center and two private orchards in Chantaburi and Trat provinces. Results from artificial pollination revealed that at anthesis, the durian flower is receptive and has a high fruit set ratio. A mean fruit set of 50% was obtained at anthesis in the private orchard in Chantaburi province. However, the EPP of durian was found to be very short, lasting for only one night; the fruit set from pollination on the morning after anthesis ranged from 0% to 3.4%. No fruit set occurred following pollination 24 or more hours after anthesis. When compared with the flowers of other fruit species, the durian flower has a unique feature in that it blooms overnight; the following morning, there is abscission of all parts of the flower, except the gynoecium. Thus, EPP appears to be synchronized with flower longevity. On the other hand, the durian flower was receptive several hours before anthesis. The results of chemical tests, including the hydrogen peroxide test and Perex-Test^®, for the evaluation of stigma receptivity appeared to be in agreement with the EPP. However, fluorescent microscopy revealed that pollen could germinate even in the stigmas pollinated 48 h after anthesis, but the number of pollen tubes at the top of the style rapidly decreased from 34.6 (at anthesis) to 0.5 (48 h after anthesis). A correlation test demonstrated a higher correlation coefficient between the fruit set and the number of pollen than that between the fruit set and the result of Perex-Test^®. This indicated that pollen tube penetration or elongation in the style was inhibited, probably due to the deterioration of nutritional support from the pistil to the pollen tubes; this can be a limiting factor of the EPP in durian.     

Effects of ethylene,abscisic acid and auxin on fruit abscission in water dropwort (Oenanthe stolonifera DC.)

Fruit abscission in water dropwort (Oenanthe stolonifera DC.) was investigated by measuring fruit removal force (FRF) affected by fruit ages and plant hormones. FRF decreased rapidly 30 days after anthesis (DAA). Ethylene evolution increased rapidly at 35 DAA and ABA concentration increased gradually after 20 DAA. ACC and ethephon decreased the FRF of fruit explants and the promoting effect of ACC was delayed by silver thiosulphate and cycloheximide, but not by norbornadiene and actinomycin D. ABA enhanced fruit abscission without increasing ethylene evolution. However, the observation that CoCl₂ delayed abscission induced by ABA indicates possible involvement of ethylene in the ABA effect. Treatment with NAA, fenoprop and IAA had no effect on 30 DAA fruit explants, but IAA delayed abscission of 25 DAA explants. This suggests that the effect of auxins may differ with fruit age when used as control agents.     

不同授粉处理对沙田柚果实发育中内源激素水平变化的影响

沙田柚自花授粉果实的重量和体积均低于异花授粉处理。与未授粉子房相比,授粉子房迅速膨大。授粉处理可使子房内源激素(ＩＡＡ)、赤霉素(ＧＡ１＋３)、细胞分裂素(ＣＴＫｓ)和脱落酸(ＡＢＡ)水平急剧上升,异花授粉处理更明显。未授粉的子房内源生长促进类激素含量保持低水平,生长抑制类激素(ＡＢＡ)水平上升,这种激素水平的失衡最终造成未授粉子房的迅速凋落。果实生长发育初期,自花授粉幼果内源激素促进类激素含量低于异花授粉处理,ＡＢＡ水平明显高出后者,果实迅速增长期间,内源ＩＡＡ和ＧＡ１＋３有两个明显的高峰期,显示ＩＡＡ和ＧＡ１＋３含量与果实迅速膨大有密切关系。果实发育后期直至成熟,内源ＡＢＡ水平逐渐升高。测定果实发育整个过程的ＡＢＡ/(ＩＡＡ＋ＧＡ１＋３＋ＣＴＫｓ),未发现规律性的变化。     

Auxin-dependent development and habituation of highbush blueberry (Vaccinium × covilleanum But. et Pl.) ‘Herbert’ in vitro shoot cultures

The influence of IAA (1.0 mg dm⁻³), and IBA (1.16 mg dm⁻³), on the development of highbush blueberry (Vaccinium × covilleanum But. et Pl.) ‘Herbert’ in vitro shoot cultures was examined. Depending on the kind of auxin and 2iP concentration in vitro cultures consisted of various number of axillary (AX) and adventitious (AD) shoots. Three different categories of AD shoots were found: leaf shoots (AD-L), node-adjoin shoots (AD-P), and base-adjoin shoots (AD-M, madshoots). The AX shoots were the least habituated (towards auxins, cytokinins and vitamins) whereas the AD-M shoots (madshoots) the most. In comparison to IAA, IBA caused dying or callusing higher number of initial explants. However, IBA generally suppressed development of AD shoots, especially madshoots whereas slightly weakened multiplication of AX shoots. IBA significantly enhanced elongation of AX shoots also. Axillary shoots obtained on IBA-media had relative long internodes and rigid, well-developed leaves. The adventitious shoots, especially base-adjoin (AD-M) ones, were easily distinguishable as were more thin and fragile, more or less vitrified, and had short internodes and smaller, sometimes unfolded leaves. Development of blueberry in vitro cultures on auxin-free and IAA-supplemented media was similar. AX shoots grown on such media resembled AD shoots. 2iP applied in higher doses along with IAA promoted much proliferation of AD than AX shoots. In contrast, 2iP applied in higher doses together with IBA stimulated significantly only growth of AX shoots whereas in general, development of adventitious shoots was not affected. Micropropagation carried out through routine method based on subculturing of shoot explants or shoot clumps on the medium supplemented with IAA (4 mg dm⁻³) and 2iP (10–15 mg dm⁻³) as well as stimulation of shoot elongation on the blank medium causes in fact the propagation of highbush blueberry through highly habituated adventitious madshoots. Replacement of IAA by IBA facilitates micropropagation of highbush blueberry cv. Herbert through axillary shoots.     

Floral induction (FI) in longan (Dimocarpus longan, Lour.) trees: Part I. Low temperature and potassium chlorate effects on FI and hormonal changes exerted in terminal buds and sub-apical tissue

Floral induction (FI) in longan (Dimocarpus longan, Lour.) trees was achieved in controlled greenhouse experiments by low temperature (LT) and by the application of potassium chlorate at high temperature (HT + KClO₃) during two consecutive seasons. The latter treatment was successful also at temperatures above 20 °C. The present experiment was conducted to investigate possible alterations in the concentrations of plant hormones exerted by these two methods and to relate them to the floral induction process. The following hormones were examined by radioimmunoassay in the shoot apical buds (SAB), and in sub-apical bark and wood: the auxin indole-3-acetic acid (IAA); gibberellins (GAs); and the cytokinins zeatin/zeatin riboside (Z/ZR) and isopentenyl-adenine/isopentenyl-adenosine (iP/iPA).