Journal of Hawaiian and Pacific Agriculture, 2008, Volume 15

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Articles

Andrea M. Kawabata, Mike A. Nagao and Laura K. Awong. 2008. Production of Male Flowers on Rambutan (Nephelium lappaceum L.) Trees in Hawai'i

Abstract: Production of deformed rambutan fruits has been attributed to poor pollination and an insufficient amount of male flowers in Hawai'i orchards.  The objectives of this study were to monitor the development of hermaphroditic functionally male (HFM) flowers on trees of the ‘Silengkeng’ cultivar, determine if naphthaleneacetic acid (NAA) could induce development of HFM flowers on cultivars grown in Hawai'i, identify the stage at which floral buds are responsive to NAA, and document the viability of pollen from HFM flowers.  Results showed that with the exception of ‘Silengkeng’, cultivars planted in Hawai'i produced few or no HFM flowers for pollination.  ‘Silengkeng’ panicles produced large numbers of HFM flowers throughout the anthesis period which made it a suitable pollinator cultivar.  NAA applied to the ‘R7’, ‘R9’, ‘R134’, ‘R162’, ‘R167’, ‘R156 Red’, ‘R156 Yellow’, ‘Binjai’, ‘Jitlee’ and ‘Rongrien’ panicles composed of predominantly hermaphroditic functionally female (HFF) flowers stimulated development of HFM flowers within 6 days after treatment.  By 12 days after treatment, production of HFM flowers was decreased.  Only floral buds at a stage in development where the apex of the pistil began protruding through the unopened sepals were responsive to NAA.  Pollen obtained from naturally produced HFM flowers on ‘Silengkeng’ panicles and from HFM flowers produced after NAA treatment was viable and germinated within 24 hours after incubation in a culture medium.  Incorporating ‘Silengkeng’ and male trees in the orchard or treating HFF panicles at the appropriate stage of development can be strategies for increasing male flowers and fruit set and reducing the development of fruit without arils.
 Keywords: , fruit set, NAA, parthenocarpic fruit.

Norbert C. Furumo and Sheldon Furutani. 2008. A Simple Method for Assaying Total Protein, Polyphenol Oxidase and Peroxidase Activity from ‘Kaimana’ Litchi chinensis Sonn.

Abstract: Polyphenol oxidase (PPO) and peroxidase (POD) are two well known enzymatic reactions involved in the browning process of fruits.  To gain a better understanding of the browning process in lychee (Litchi chinensis Sonn.), effective methods to extract PPO and POD must be developed.  Pericarps from thawed ‘Kaimana’ lychee were suspended in 100 mM potassium citrate buffer pH 4.0 and homogenized.  The soluble extract was assayed for total protein, PPO and POD enzymes.  For fresh fruit, 0.16 ± 0.02 mg protein/mL of extract was measured which is equivalent to an average of 0.81 ± 0.11 mg protein/g of peel.  PPO specific activity was 167 ± 44 U/mg protein (or an average of 130 ± 31 U/g peel) and POD activity was 13.1 ± 1.8 U/mg protein (or an average of 10.1 ± 0.3 U/g peel).   Use of 4-methylcatechol for PPO activity and guaiacol for POD activity are described for assaying lychee pericarps.
Keywords: Litchi chinensis Sonn, Kaimana, Mauritius, lychee, polyphenol oxidase, peroxidase, pericarps.

N. V. Hue. 2008. Development, Impacts and Management of Soil Acidity in Hawaii

Abstract: Soil acidity is a serious constraint to crop production and ecosystem health. Acidification can occur naturally via the formation of carbonic acid (CO2 + H2O -> H2CO3 -> HCO3- + H+) and subsequent leaching of basic cations or through man-made processes. These include the formation of sulfuric and nitric acids by coal burning, automobile exhaust emission, and applying ammoniacal fertilizers. Given the warm temperatures and humid conditions, most Hawaii soils are acidic, having either aluminum (Al) and/or manganese (Mn) toxicities or calcium (Ca) deficiency. Aluminum toxicity usually damages the root system first; in contrast, Mn toxicity affects above-ground parts of a plant. Calcium deficiency shows up more clearly at growing points owing to the relative immobility of this nutrient. Productivity of these acid soils can be improved by either adding lime or planting acid-tolerant crops. Several lime titration curves are presented for Hawaiian soils, also some acidity tolerant crops are discussed.

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