Ph.D. - Horticulture

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    Genetic Improvement of Leucaena SPP. and Acacia Koa Gray as High-Value Hardwoods
    ( 2003) Shi, Xuebo
    Studies on genetic improvement of Leucaena and Acacia koa Gray were undertaken in Hawaii from 1999-2003. There studies were described in two sections. The first section focused on research of Leucaena hybrids, which included vegetative propagation of Leucaena hybrids, hybrid yield trials, and chromosome doubling of diploid Leucaena species. Different hybrids rooted differently. Cuttings with more leaf presence had higher rooting frequency, better root qualities, and quicker root initiations. Leafless cuttings did not root under a mist system. One-node cuttings rooted as well as bi-nodal cuttings. Cuttings from younger (25-45 days old) regrown shoots rooted better than cuttings from older shoots (>45 days old). All hybrids rooted poorly in winter. Difficult-to-root hybrids rooted well after the treatments of etiolation. Three hybrid yield trials using clones of hybrids were carried out at three locations, Waimanalo of Oahu, and Hamakua and Kona of Hawaii Island. Seedless hybrid KI 000 grew best at warm areas of Waimanalo and Kona, but grew poorly at cool area of Hamakua in terms of DBH, height, and wood volume. Two tetraploid hybrids, KX3 cl2 (L. leucocephala x L. diversifolia) and K I56 x K376 (L. diversifolia x L. pallida) were among the fastest-growing hybrids at Waimanalo and Hamakua. The method (0.1% colchicine treatments on seedlings) to induce tetraploid Leucaena species was effective. Larger, thicker and darker leaflets, and larger flower heads of induced tetraploids were observed. The second section focused on studies of koa, which included cytological study of koa, vegetative propagation, koa mortality and tolerance to wilt disease, and prediction of breeding values of koa. No variations in chromosome number were found among three koa types and populations. The chromosome number of koa was identified as 2n=52 among all populations examined. Koa vegetative propagation was feasible at juvenile stage. Rooting ability of cuttings declined quickly with the increase of the age of cuttings. Cuttings of most families did not root at transitional and mature stages, and they did not respond to the treatments of growth regulators. Only cuttings of two families from Hawaii Island responded to auxins well with a moderate increase in rooting percentage at transitional and mature stages. Etiolation treatments appeared to have some effects on rooting at transitional stage. Koa survival rates in progeny trials declined steadily over the years. The mortality appeared to be mainly caused by koa wilt disease. The survival rates of koa families were analyzed and used to assess family tolerance to the disease. Great variation in survival rate was found among the families. Family selection based on survival rate was conducted. To rank the growth performance of koa families in progeny trials, breeding values of DBH at the age of 4 years were predicted in 4 progeny trials using BLP (Best Linear Prediction) method. Family ranking and selection based on predicted breeding values were conducted. Genetic gains of selection were calculated based on family selection.
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    Source-sink Relationship During Papaya Fruit Development and Ripening
    ( 1999) Zhou, Lili
    The source sink relationship during papaya fruit development and ripening was investigated. The source size and sink strength were modified by single or continual defoliation, and fruit thinning, respectively. The relationship between fruit growth, respiration, sugar accumulation and the activity of sucrose phosphate synthase (SPS), sucrose synthase (SS), and acid invertase were determined in fruit from 14 days after anthesis (DAA) to 140 DAA (harvest maturity) and in response to defoliation and fruit removal. A putative complete invertase gene and a SS gene fragment were isolated and characterized from nearly mature green papaya fruit. Single defoliation significantly reduced new flower and fruit set, and ripe fruit total soluble solids (TSS) but did not reduce fruit production, average fruit mass, percentage fruit flesh and seed, seed mass ratio and seed dry mass during a six weeks period. Continual defoliation in addition reduced fruit size, sugar and invertase enzyme activity and fruit production. The responses of defoliation and fruit thinning varied between different cultivars, weather conditions, defoliation time, degree and method. The pattern of gene expression during fruit development was compared with invertase extracted enzyme activity in the presence and absence of sodium chloride (NaCI) and by western blot analysis. The papaya invertase sequence had an open reading frame that encoded a polypeptide chain of 582 residues and calculated molecular weight of 65, 684 Da. The protein was highly homologous to known plant cell wall invertase and 67% identical at the amino acid level to carrot cell wall invertase. The cloned 720 bp SS fragment was highly homologous to A. glutinosa (X92378) and SS genes from other species. Invertase gene was expressed at a higher level during late fruit development stage than in young fruit and other tissues of papaya plant. SS gene expression was higher in young fruit and petiole tissues than in other tissues. The data demonstrated that SS enzyme was a major enzyme in fruit sink establishment and maintenance. Apoplastic invertase had an important function in phloem unloading during papaya fruit sugar accumulation and the activity was regulated at both transcriptional and translational levels.
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    Breeding for Papaya Ringspot Virus Tolerance in Solo Papayas, Carica papaya L.
    ( 1985) Zee, Francis T.P.
    A high degree of Papaya Ringspot Virus (PRV) tolerance was observed in a dioecious Carica papaya, line 356, introduced from Florida. Upon infection with the virus, plants of line 356 produced mild leaf, stem and fruit symptoms. Fruit distortion was not observed on these plants. Selected females of line 356 were crossed with 'Kapoho', 'Higgins' and 'Waimanalo' to produce lines 402, 410 and 403, respectively. The level of virus tolerance in these hybrids was observed to be intermediate between the 356 and solo parents. A few selected F2 plants had significantly higher PRV tolerance than the solo parents and only a few trees produced distorted fruits. The F2 plants from 402DF1 and 410AF1 were more tolerant to PRV than 403F1 and derived F2's. Selected 410AF2 trees had the highest virus tolerance among the hybrids but fruit quality was unacceptable. The 402DF2 plants were intermediate in virus tolerance, but produced fruits with good eating quality. The cool climate at the Olinda station in Maui provided good growing conditions for 5 wild Carica species and one interspecific hybrid, but did not permit successful interspecific hybridization between Carica papaya and other species. Carica papaya was crossed with C. pubescens, C. monoica and a C. cauliflora x C. monoica hybrid, resulting in fruits with a few seeds, but no viable hybrid plant was produced. The extraction buffer for C. papaya in ELISA was not suitable for PRV detection in other Carica species. Leaf homogenates from C. pubescens and microcarpa were observed to have a certain compound that interfered with PRV detection when mixed with a PRV standard. The higher the concentration of pubescens homogenate in the mixture, the higher the interference effect. This interference compound appeared to interfere with the PRV-y-globulin, is not protein specific and can be destroyed by heat.
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    Herbicidal Activity and Translocation of Glyphosate in Cyperus Rotundus l.
    ( 1976) Zandstra, Bernard Henry
    Purple nutsedge (Cyperus rotundus L.) plants grown in the greenhouse were treated with 4 kg/ha glyphosate [N-(phosphonomethyl) glycine] or 2.2 kg/ha paraquat (1,1'-dimethyl-4,4'-bipyridinium ion). Glyphosate greatly reduced fresh weight of leaves, number of sprouts per original tuber, and number of sprouts per new tuber. Paraquat reduced fresh weight of leaves about as well as glyphosate, but was not as effective in reducing germination of tubers. Glyphosate at 2 and 4 kg/ha was compared in the field to paraquat, dicamba (3,6-dichloro-o-anisic acid), and MSMA (monosodium methanearsonate) for purple nutsedge control in repeated applications over 8 months. After two applications glyphosate had greatly reduced the number of plants. The other herbicides were not as effective in reducing number of shoots. At 5 months, after the field was rotovated and herbicides reapplied, glyphosate and MSMA gave better control of purple nutsedge plants than the other herbicides. Glyphosate and MSMA also reduced germination of tubers from treated plants. After five applications, glyphosate and MSMA reduced germination by 70%, and dicamba reduced germination by 43%. Paraquat did not reduce germination. Since glyphosate gave good control of purple nutsedge, further studies were conducted to determine the most effective rate of glyphosate, and the most susceptible age of purple nutsedge at application. Purple nutsedge was treated with glyphosate at 2, 4, 6, 12, or 24 weeks after field preparation. Glyphosate was reapplied at 2, 4, 6, or 12 week intervals, respectively, until no shoots emerged. Plants were counted in treated plots every 2 weeks, and tubers were dug every 4 weeks. These tubers were germinated to test viability by placing them in Petri dishes and incubating with 100 ppm N-6 benzyl adenine. All purple nutsedge plants treated at 12 weeks old were killed by glyphosate at 2 and 4 kg/ha, as evidenced by no regrowth of shoots, and almost no germination of tubers. Control of purple nutsedge in plots treated at 2 to 6 weeks old was less effective and several applications of glyphosate were needed to achieve good control levels. Application of glyphosate at 24 weeks killed purple nutsedge foliage, but new growth emerged immediately. Generally, application of glyphosate every 2 weeks reduced plant numbers more rapidly than every 4 or 6 weeks. Rates of 1, 2, and 4 kg/ha were equally effective in reducing number of plants after several applications, but 2 and 4 kg/ha were more effective with fewer applications. Two kg/ha gave as good control as 4 kg/ha. Viability of tubers from plants treated at 2 to 6 weeks old was higher than of tubers from plants treated at 12 weeks old. Applications of glyphosate at 24 weeks did not reduce viability of tubers. The field was rotovated 10 months after the initial preparation, and the purple nutsedge allowed to regrow. Regrowth was rapid in all plots. However, all plots treated with glyphosate except those treated at 24 weeks, produced less regrowth than the controls. Succeeding experiments carried out in the greenhouse further examined the effects of age and stage of purple nutsedge growth on its control with glyphosate. Tubers from purple nutsedge plants grown in the greenhouse for 2 to 10 weeks did not germinate after foliar application of glyphosate. Some tubers from, plants 12 and 24 weeks old survived glyphosate application. 14C-glyphosate was used to study translocation of glyphosate in 1-to 6-week-old purple nutsedge plants. Translocation of –glyphosate from treated leaves increased from 5% of the amount applied at 1 day to 19% at 4 days after application. Specific activity of in tubers was greater than in leaves at all growth stages. With increasing plant age, specific activity decreased in both tubers and leaves. Also with increasing plant age, total translocated increased in tubers, and decreased slightly in leaves. Thin layer chromatography showed no evidence of glyphosate metabolism in purple nutsedge. These results indicated that stage of growth is an important factor in obtaining control of purple nutsedge with glyphosate. Purple nutsedge in the field was most susceptible 12 weeks after the field was prepared. Purple nutsedge grown in the greenhouse was most susceptible at 2 to 10 weeks after planting. Evidently the stage of growth, or physiological age of the plant, is more important than chronological age. Once purple nutsedge plants have flowered, senescence sets in, and effectiveness of glyphosate declines.
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    Ovule and Ovary Culture in Doritis Pulcherrima
    ( 1980) Yasugi, Saburo
    Pollination resulted in an increase in size of ovary, the development of the ovules and fertilization in Doritis pulcherrima. The growth curve of percentage increase in total growth of ovary width was bimodal. The first dip was at 40 days after pollination which was correlated with the time of megaspore formation inside the ovary. The growth curve of increase in percentage of ovary length was trimodal. These growth curves did not show a strong relationship with the development of ovule and embryo. However, the incremental growth in width and length of ovary was highest during rudimentary ovule formation and before embryo sac maturation. The mature pod dehisced at about 210 days after pollination, while the incremental growth in width and length stopped at about 90 to 110 days after pollination. Wilting of perianth occurred 2 days after pollination, which is the first observable morphological change in Doritis. The placental ridge started to proliferate at about 20 days after pollination. Approximately 60 days was required to form the mature embryo sac and almost half of that time was occupied in placental growth. Although the pollen tubes existed around developing ovules at 10 days after pollination, they entered the micropyle after the embryo sac was fully formed at about 60 days after pollination. Fertilization occurred soon after the embryo sac was fully formed containing mature egg at 60-65 days after pollination. Therefore, approximately 1/4 of the period between pollination and pod maturity was required for fertilization. Between 40 to 50 days after pollination, the megaspore mother cell underwent meiosis. After the first division, the two dyads were formed, and after the second division two megaspores and the degenerating dyad was formed. The megaspore enlarged and formed the 8-nucleate embryo sac at about 60 days after pollination. At about 65 days after pollination, the zygote and the endosperm initial cell were formed through double fertilization. However, the endosperm initial cell degenerated soon thereafter. At about 70 days after pollination, the zygote divided to form a 2-celled embryo which consisted of a terminal cell and a basal cell. Thin middle and suspensor initial cells were produced from the basal cell. The seed coat was also formed at about 70 days after pollination from the integuments. At about 80 days after pollination, the suspensor initial cell produced eight suspensor cells, and the terminal cell produced a multi-celled embryo. Histochemical study showed that deoxyribonucleic acid (DNA), ribonucleic acid (RNA), total proteins and total carbohydrates decreased during megasporogensis. An interesting point was that RNA was more dense in the terminal cell than in the basal cell, which suggested that the initial differentiation had already occurred in the 2-celled embryo This is the first case of obtaining seedlings of orchids directly from ovules through ovary and ovule culture with ovules collected prior to the occurrence of fertilization. Approximately 150 days were reduced to obtain seedlings of Doritis pulchcrrima from pollination through ovary and ovule culture over the traditional method of sowing "mature" seeds. Seedlings were obtained from ovules 45 days prior to normal fertilization time through ovary and ovule culture, which suggested that fertilization must have occurred in vitro during ovary and ovule culture to obtain seedlings. In the 20-day-old ovule culture, young seedlings were obtained from the treatments of sucrose; naphthaleneacetic acid (NAA) + coconut water; and NAA + 6-benzlaminopurine (BA) + coconut water. However, the growth rate of ovules during culture was not high in these treatments. In the 40-day-old ovule culture, the treatments of sucrose; coconut water; and NAA + BA + sucrose + coconut water were highly effective on both ovule growth rate and seedling formation. In the 60-day-old ovule culture, seedlings were obtained from all treatments except NAA; BA; and NAA + BA. Good growth of ovules did not always induce good seedling formation. Seedlings were obtained from 20-, 40- and 60-day-old ovule cultures if media contained sucrose or coconut water. Sucrose must be necessary for seedling formation during ovule culture, since coconut water contains sucrose. However, if we compare the time required to obtain seedlings, coconut water promoted faster growth than sucrose alone in ovule culture. Maleic hydrazide, tryptophan, casein hydrolysate, NAA and BA were not effective on seedling formation without sucrose or coconut water. The best hormonal conditions for obtaining seedlings in ovary culture were 1.0 ppm BA in 20-day-old ovary culture, 1.0 ppm NAA in 40-day-old ovary culture, and 1.0 ppm NAA in 60-day-old ovary culture. BA was more effective than NAA in forming seedlings in early stage (20 days after pollination) during ovary culture. Coconut water was also effective in ovary culture to obtain seedlings. However, it also increased callus formation rate. Sucrose was necessary in ovule culture to obtain seedlings. However, even without sucrose seedlings were obtained through ovary culture with NAA or BA treatments. Therefore, sucrose might be necessary for ovule development and seedling formation, but in the case of ovary culture sucrose might be obtained from the ovary wall tissues. Sucrose was also necessary for seed germination, but coconut water can be substituted effectively for seed germination and protocorm formation. Sucrose appears to have a very important role in ovule and embryo developments and seedling formation.
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    Productivity of Vegetable Crops Grown under Shade in Hawaii
    ( 1988) Wolff, Xenia Yvette
    Waimanalo Long' eggplant (Solanum melonaena L.), 'Kahala' soybean ^Glvcine max (L.) Merrill), 'Jumbo Virginia' peanut (Arachis hvpoaea L.), 'Waimanalo Red' sweet potato flpomea batatas (L.) Lam.), and 'Green Mignonette' semihead lettuce fLactuca sativa L.) were field-grown in two seasons at Waimanalo, Oahu, Hawaii with five artificially produced levels of shade (0, 30, 47, 63, and 73%). Yields and vegetative growth of eggplant, soybean, peanut, and sweet potato were linearly decreased with increasing shade levels. Compared to unshaded controls, yields of semihead lettuce increased significantly from 8100 kg•ha-1 to 13,600 kg•ha-1 by 30% shade in Fall 1986. During Spring 1987, semihead lettuce yields were reduced only slightly from unshaded levels of 22,000 kg•ha-1 by increasing shade up to 47%. Eggplant, soybean and lettuce maintained index leaf areas similar to unshaded controls as shade intensity increased, at the expense of leaf dry weight. By comparison, both leaf area and leaf dry weight of peanut index leaves decreased as shade increased. Leaf area and leaf dry weight of sweet potato did not respond to shading. To further investigate the effects of shade on leafy vegetables, 'Green Mignonette', 'Salinas', 'Parris Island Cos', and 'Amaral 400' lettuce (Lactuca sativa L.), 'WR-55 Days' Chinese cabbage (Brassica raoa L. Pekinensis Group), 'Waianae Strain' green mustard cabbage (Brassica iuncea (L.) Czerniak), 'Tastie Hybrid' head cabbage (Brassica oleracea L. Capitata Group), and an unnamed local selection of bunching onions (Allium ceoa L. Aggregatum Group) were field-grown in two seasons at the same location with the same five artificially produced levels of shade. Yields of cos lettuce, green mustard cabbage, and bunching onions were irresponsive or negatively affected by shade in both seasons. Yield responses of the other crops to shade varied seasonally. Optimum shading of 30 to 47% increased 'Green Mignonette', 'Salinas', and 'Amaral 400' lettuce by 36% and head cabbage and Chinese cabbage yields by 23% and 21 %, respectively, compared to full-sun plots in some trials. Index leaf areas similar to unshaded controls were maintained as shade intensity increased, at the expense of leaf dry weight in all crops except 'Salinas' and 'Parris Island Cos' lettuce. Maximum rates of net photosynthesis (Pn) were attained at about two-thirds of full sunlight (1500 umol • s-1•m-2).
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    Ammonium Sulphate Enhancement of Picloram Herbicidal Activity and Absorption in Two Guava Species and Dwarf Beans
    ( 1974) Wilson, Bruce James
    Studies were conducted to increase picloram herbicidal activity on guava (Psidium guajava L.), strawberry guava (Psidium cattleianum Sabine) and dwarf beans (Phaseolus vulgaris L. cv. Bountiful) using ammonium sulphate as an adjuvant, and to determine the basis for the enhancement effect. Guava and strawberry guava seedlings were grown in pots outdoors for 3 to 4 months and 4 to 5 months respectively, and subsequently in the glasshouse for 2 months, before treatment with picloram alone at 0.25 , 0.50 and 0.75 kg a.i. /ha, or plus ammonium sulfate at 0.10, 0.75, 1.0 and 10% (w/v). Dwarf beans were treated with picloram alone at 0.02 and 0.04 kg a.i. /ha, or plus ammonium sulfate at 0.10, 0.50, 1.0, 5.0 and 10% (w/v). Ammonium sulfate increased picloram herbicidal activity in all three species to varying degrees, depending on picloram rate and ammonium sulfate concentration. Picloram injury was enhanced by ammonium sulfate at all picloram rates shortly after treatment. The higher picloram rates continued to increase injury with time, so that by the end of the experiment on each species, the maximum effect was attained without ammonium sulfate and an- enhancement effect could not be demonstrated. The enhancement effect remained evident at the low picloram rates. Ammonium sulfate concentrations of 0.75% to 1.0% and higher were equally effective at increasing picloram activity at the end of each experiment, but at earlier times, picloram activity increased with increasing ammonium sulfate concentration up to 10%. Paired leaves on the upper stem of strawberry guava and guava seedlings were treated with 14C-picloram alone or plus ammonium sulfate at 0.5% and 10% (w/v) on strawberry guava, and 0.5$ on guava. The 14C-picloram acid was converted to the potassium salt using commercial formulation blank, so that the 14C solutions were equivalent to the picloram solutions used in the activity experiments. After 2 days on strawberry guava, 0.5% ammonium sulfate increased 14C-picloram absorption about five-fold. There was about four times more 14C in the upper stem and attached leaves with ammonium sulfate added than with picloram alone. 14C-picloram absorption from 0.5% and 10% ammonium sulfate treatments was equal. Ammonium sulfate at 0.5% increased picloram absorption by four-fold in guava, but there was no increase in the amount of 14C translocated. All the 14C in both guava species was shown to be 14C-picloram by paper chromatography of extracts. Picloram absorption by dwarf beans, measured by difference between the amounts of picloram applied and the amount recovered, was increased by 0.5% and 10% ammonium sulfate by a similar magnitude as on guava species. Picloram absorption was further studied using detached strawberry guava leaves, and guava leaves in an initial experiment. 14C-picloram absorption was greater through the lower surface than through the upper surface, with or without ammonium sulfate. In strawberry guava leaves, 14C-picloram absorption through the upper and lower leaf surfaces was equal, but the ammonium sulfate enhancement of absorption was much greater through the upper surface. Ammonium sulfate increased the rate of 14C-picloram absorption, but absorption from 14C-picloram alone or plus ammonium sulfate levelled off at 6 to 12 hours. The magnitude of the ammonium sulfate-induced increase in 14C-picloram absorption was not affected by picloram concentration in the range 250 to 2000 ppmw, or by leaf age. 14C-picloram absorption by this detached leaf method was highest at an intermediate ammonium sulfate concentration range, such that absorption with 0.1% and 10% ammonium sulfate was less than with 0.5%; 0.01% had no effect on absorption. Increased 14C-picloram absorption resulted from adding the ammonium salts of sulfate, nitrate, chloride or dibasic phosphate, but not from ammonium carbonate or ammonium molybdenate. Ammonium sulfate was the only one of six sulfate salts tested to increase picloram absorption. pH adjustment of the external solution from 6 to 4 increased picloram absorption, while a pH change from 6 to 8 had no effect. In buffered solution at pH 4 ammonium sulfate did not increase 14C-picloram absorption. Ammonium dibasic phosphate at a solution pH of 7.7 increased picloram absorption as effectively as ammonium monobasic phosphate at pH 4.6. Potassium monobasic phosphate at pH 4.6 increased absorption to about one-half the value with ammonium phosphates added, whereas potassium dibasic phosphate at pH 9.5 had no effect. Stomata are not present on the upper surface of strawberry guava leaves, thus in the measurement of the effect of ammonium sulfate on picloram absorption, cuticular penetration of picloram must have been involved. The evidence suggests that ammonium sulfate has a direct physical effect in the absorption pathway.
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    Genome and Karyotype Relationships in the Genus Dendrobium (Orchidaceae)
    ( 1968) Wilfret, Gary Joe
    Investigations on sexual compatibility, karyotype analysis, and genome relationships were made with species in the genus Dendrobium of the family Orchidaceae. A hybridization study was made utilizing 38 species of 10 taxonomic sections in 48 combinations. A total of 783 pollinations was made with 164 fruits harvested, of which 113 produced viable crosses. Five intrasectional and 20 intersectional combinations resulted in viable seedlings. The Eugenanthe x Eugenanthe combination showed little compatibility among the species within the section and showed equal or more compatibility with the Ceratobium, Phalaenanthe, and Pedilonum sections. Species in the Ceratobium section crossed as readily with species in the Phalaenanthe section as within the Ceratobium section. The percentage of non-aborted embryos was determined for each fruit harvested. The separation of all the species into the classical taxonomic sections of the genus was not possible on the basis of their cross ability or percentage of non-aborted embryos. Chromosome numbers of 33 species in 11 sections were determined, of which 31 were 2n=38 and 2 were 2n=40. Five of these had not previously been reported. Detailed examinations of chromosome morphology were made of 23 species in 11 sections. The mean chromosome size was as variable within the sections as between the sections. The sections could not be distinguished-by the average chromosome length of their constituents. No relationship was found between chromosome size and geographical and climatological distribution in the species studied. A mean S% and F% for each species and the average for each section was calculated. Individual sections could not be distinguished on the basis of S% and F7» although a few individual species could be detected by these values in conjunction with other morphological characteristics of the karyotypes. The evolution of the karyotypes was not reflected in the external morphological specializations of the sections. Meiosis in four intrasectional Ceratobium hybrids consistently showed 19 bivalents and the products of meiosis were normal tetrads with 19 chromosomes distributed to each microspore. Five intersectional Phalaenanthe x Ceratobium hybrids displayed an average of 16.80 bivalents and 4.40 univalents. Microspore division exhibited an average of 93.2% tetrads and 3.9% dyads, with tetrads and dyads with microcytes also observed. Meiosis in a Phalaenanthe x Latourea hybrid showed 2.06 bivalents and 33.88 univalents with the products of meiosis being tetrads, dyads, and tetrads and dyads with microcytes. Heterochromatic and heteroraorphic bivalents were observed in the intersectional hybrids. The results indicated that the genomes within the Ceratobium are closely homologous; the genomes of Ceratobium and Phalaenanthe are closely related; and the genomes of Latourea are more closely related to Ceratobium than Phalaenanthe.
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    Influence of Vesicular-arbuscular Mycorrhizae on the Growth and Water Relations of Vegetable Crops
    ( 1988) Waterer, Douglas R.
    Onion, leek, pepper, lettuce and tomato transplants grown in a soilless medium inoculated with the VAMF Glomus aggregatum (Schenck and Smith emend. Koske) were larger and had higher tissue phosphorus (P) concentrations than non-inoculated plants if P levels in the medium were low. At higher P concentrations, inoculation had little or a slightly negative effect on transplant growth. Increasing P concentrations in the medium increased transplant growth, but decreased root infection by the VAMF. Increasing VAMF inoculvim concentrations did not affect growth or P uptake but increased VAMF infection of the transplants. Daily application of low P fertilizer solutions produced larger transplants with more extensively infected root systems than did similar amounts of P supplied less frequently but at higher concentrations. Different crops required different combinations of P concentration and application interval to produce vigorous mycorrhizal transplants. The controlled-release fertilizer Osmocote (Sierra Chemical Co., Milptas Calif.) produced predictable and stable solution P concentrations in the soilless medium used for transplant production. Growth and VAMF infection of the transplants could be manipulated by altering Osmocote P concentrations in the transplant medium. Pre-transplant inoculation of peppers subsequently planted into P deficient soil improved early P uptake, vegetative growth and total fruit yields relative to plants inoculated at transplanting. In P deficient soils, maximum pre-transplant VAMF infection of peppers increased subsequent growth and fruit yields more than maximum pre-transplant growth. Extensive pre-transplanting infection improved post-transplant P uptake earlier than in less heavily infected plants. In contrast, pre-transplant growth of lettuce was more important than mycorrhizal infection in determining subsequent growth, at all soil P levels. In pots, G. aggregatum increased total dry matter yields, promoted early fruit set and improved fruit yields of peppers at solution P concentrations below 0.3 to 0.4 mg/liter. At higher P concentrations, VAMF infection had no beneficial or harmful effects. Tissue P requirements for dry matter production by mycorrhizal plants were lower than in non-mycorrhizal plants, suggesting that mycorrhizae may influence the efficiency of utilization of absorbed P in addition to increasing P uptake efficiency. In the field, inoculation of peppers increased tissue P concentrations, growth and fruit yields by 28, 120 and 350% respectively relative to non-mycorrhizal plants in a fumigated P-fixing soil with 0.03 mg/liter solution P. Inoculation had no significant effect at 0.30 mg P/liter. Under similar conditions, VAMF infection increased yields of lettuce by 16%. Although non-mycorrhizal lettuce and peppers had similar solution P requirements for maximum growth, lettuce was more tolerant of sub-optimal solution P concentrations and was correspondingly less responsive to infection by the VAMF. Moderate water stress increased mycorrhizal responsiveness of peppers growing in P deficient soil. VAMF colonization of pepper seedlings growing in P deficient media increased the hydraulic conductivity of their roots, possibly by improving seedlings tissue P status. Mature mycorrhizal peppers had higher rates of transpiration per unit leak area than similar size non-mycorrhizal plants. At wilting, mycorrhizal transplants and mature peppers had higher leaf water potentials at lower soil water potentials than non-mycorrhizal plants. The influence of mycorrhizae on the water relations of mature peppers was apparently related to the mycorrhizae improving P uptake by their host but the change in water relations of inoculated seedlings was generally independent of host P-status.
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    Biochemical and Genetic Analyses of Lavender-purple Spathes in Anthuriums
    ( 1988) Wannakrairoj, Sura Wit
    Systems controlling lavender-purple spathe color in anthuriums were investigated biochemically and genetically. Regression analysis of biochemical data showed that the blueness of anthurium spathe color was the result of cyanidin 3-rutinoside and its interaction with cell sap pH and major flavonoids from A. amnicola, A. andraeanum and A. antioouense. The ratio of cyaniding 3-rutinoside to acacetin C-diglycoside was found to be the most important factor determining the degree of blueness in the regression model. Results from in vitro copigmentation experiments suggested that the inhibition effect of acacetin C-diglycoside may be due to some unknown factors strongly associated with the flavone. A. amnicola and A. antiocfuense of section Porphvrochitonium, and A. andraeanum and A. formosum of section Calomystrium were shown to be closely related based on their crossability and on the meiotic behavior of hybrids. All interspecific hybrids showed 15 bivalents at metaphase I; however, some hybrids showed spindle abnormalities. Interspecific progenies of A. amnicola produced the lowest percentage of viable pollen. A genetic scheme controlling lavender-purple spathe color was proposed. The system consisted of two loci controlling red-orange-white colors and a recessive epistatic locus for the copigmentation inhibitor. General combining ability of parental species for the quantity of the factors involved in color expression was determined.