Vegetative and Reproductive Response of Lycopersicon esculentum Mill. to Photoperiods

The photoperiodic behavior of tomato cultivars differing ingrowth habit and geographical origin was investigated. Short(8 h) and long (11 to 14 h or dark interruption) photoperiodswere obtained by using the changing seasonal daylenghs. Observationson vegetative and reproductive development indicated that thetomato cultivars responded differentially to the treatments.A highly significant interaction between photoperiod and leafposition was observed. The probable cause for the diverse andcomplex responses of the tomato species to photoperiods is discussed.     

Influences of Certain Plant Factors on the Growth and Fruiting of the Lower Axillary Shoot of Lycopersicon esculentum Mill

Excision of the first inflorescence at diffrent stages of development,emasculation of the anthers before anthesis, and excision of of the entire root system at transplanting significantly enhahcedthe growth and fruiting of the axillary shoot located directlybelow the first inflorescence of Lycopersicon esculentum Mill.cv. Fireball. Replacement of the inflorescence with a combinationof indol-3yl-acetic acid, gibberellin A_4/7 and N⁶-benyladenineat 5 x 10^–4 M concentration in lanolin delayed the timefor the axillary shoot to attain a length of 20 cm. Enchancementof growth and fruiting of the auxillary shoot below the firstinflorenscence was attributed to a greater availability of assimilate.     

The Abscisic Acid Content of Citrus with Special Reference to Lemon

Free and conjugated abscisic acid (ABA) in the fruit peel offour species of citrus and their distribution in the variousreproductive organs of Citrus limon L. cv. Eureka during ontogenywere determined by an indirect enzyme-linked immunosorbent assay(ELISA). The different citrus species varied in free ABA (3-8g g dry wt.) and conjugated ABA (10-39 /xg gl dry wt.). In general,the amount of conjugated ABA was 4-fold that of free ABA. Inthe lemon flower, the combined style and stigma tissues containedthe predominant (>65%) amount of both free and conjugatedABA. During fruit development, free and conjugated ABA of thedifferent tissues showed dynamic changes. In the vesicles, freeABA showed progressive increases with development and reacheda high level at maturity whereas the conjugated ABA showed acorresponding decrease with fruit development. Free ABA in theseed increased with fruit development. The content of ABA incitrus fruit was significantly correlated ( = 8.06 + 2.81 Inx; /-2 = 0.84^**) with the weight of the fruit Key words: Abscisic acid, citrus species, reproductive organs, development     

The Nature of Root-Promoting Substances in Lycopersicon esculentum Seedlings

Determination of the organ sites and chemical nature of root-promoting substances in Lycopersicon esculentum seedlings was made. Results of organ excision indicated that the young cotyledons were the primary site of root-promoting substances. As the cotyledon matured, its root-promoting activity decreased while that of the developing plumular leaves increased. Application of 2,3,5-triiodobenzoic acid (TIBA) at 10^?3 M in lanolin to the hypocotyl below the cotyledonary node significantly prevented root formation. Bioassay, using a new tomato rooting test, of the basic, acidic and bound fractions of the cotyledon extracts after paper chromatography showed biological activities in all three fractions. Gas-liquid chromatography of selected active regions of the paper chromatogram resulted in a partial tentative identification of indolepropionic acid, 5-methylindole, 5-hydroxy-indole and 3-indoleacetonitrile. The combined evidence indicated that the root-promoting substances in tomato seedlings resemble auxin compounds.     

Effects of carbonyl sulfide, methyl iodide, and sulfuryl fluoride on fruit phytotoxicity and insect mortality

Three potential chemical fumigants: carbonyl sulfide (COS), methyl iodide (MI) and sulfuryl fluoride (SF) were tested at selected dosages on lemons against California red scale (Aonidiella aurantii) and MI and COS were tested on nectarines against codling moth (Cydia pomonella). In nectarines, COS was tested at 0, 20, 40, 60 and 80 mg litre^?1, MI at 0, 10, 15, 20 and 25 mg litre^?1. Both fumigants intensified nectarine peel color, delayed fruit softening, but did not alter overall fruit quality. COS at 80 mg litre^?1 resulted in 87% codling moth mortality, but the fumigant dosage was insufficient to reach the desired probits 9 level (99.9968%). MI gave 100% codling moth mortality at 25 mg litre^?1. Lemons were treated with MI at 0,10,20,40,60 mg litre^?1, SF at 0,10,20,40, 80 mg litre^?1 and COS at 0,20,40, 60 and 80 mg litre^?1. MI gave 100% red scale mortality at ≥40 mg litre^?1 but caused significant fruit injury. Conditioning lemons at 15°C for 3 days before MI fumigation lessened lemon phytotoxicity. Forced aeration at 3.5 standard litres per minute of lemons for 24 h following MI fumigation at 20 mg litre^?1 significantly reduced phytotoxicity compared to 2 h postfumigation aeration after MI treatment. SF at ≥40 mg litre^?1 gave 100% red scale mortality but resulted in commodity phytotoxicity. Lemons treated with the highest selected dose of 80 mg litre^?1 COS gave only 87% kill of red scale, but failed to reach the desired probit 9 level.     

A Broad Spectrum Tissue Culture Experiment with Tobacco (Nicotiana tabacum) Pith Tissue Callus

The composition and rationale of a broad spectrum tissue culture experiment involving 81 different media are described. Tobacco calluses sub-cultured on media in this experiment were induced to form six main types of callus depending on the concentration levels of minerals, auxins, cytokinins, and sucrose, growth factors and amino acids in the medium. Only nine of the 81 media inhibited callus growth, and growth (increase in mass divided by initial mass of fresh matter) varied considerably reaching a maximum of nearly 200 after eight weeks on a medium high in minerals, cytokinins, sucrose, growth factors and amino acids and low in auxins. Five media induced regeneration from the calluses. This experiment is suggested as a potentially fruitful introductory test for many new or unresolved tissue culture situations.     

Changes in Endogenous Gibberellin Levels in Tulipa Bulblets during Ontogeny

The endogenous gibberellin activity of Tulipa gesneriana cv.Apeldoorn bulbiets of field-grown mother bulbs was determinedduring ontogeny by paper and gas-liquid chromatography and thedwarf pea bioassay. It was shown that the gibberellin activityof bulblets increased dramatically in November-March and declinedsharply in April-July. The increase in gibberellin-like substanceswas considered to be derived primarily by synthesis within thebulblets with possible contributions via translocation fromthe mother bulb scales, roots and shoots. Gibberellin A₁₃ wastentatively identified by gas-liquid chromatography but theother components of the bulbiet extracts remained unidentified.     

The Effects of Sodium 2,3-Dichloroisobutyrate on Microsporogenesis and Fruit Set in Lycopersicon esculentum Mill

Histological and histochemical examinations of sodium 2,3-dichloroisobutyrate(DCB)treated tomato floral buds at various stages of developmentshowed that DCB affected the development of microspores andtapetal cells. DCB at 0.075 and 0.15% resulted in the formationof uninucleate microspores, absence of microspore starch, retardationof exine formation, degeneration of microspore cytoplasm, anda delay in the breakdown of the tapetum. Embryo sac developmentwas unaffected by DCB. The interference of carbohydrate metabolismby DCB was indicated. Reduction of fruit set by DCB was causedby abnormal or lack of pollen formation.