Female Flower Appearance Research Articles

Correlações genotípicas, fenotípicas e de ambiente entre dez caracteres de melancia e suas implicações para o melhoramento genético

Foram estimadas as correlações genotípicas, fenotípicas e de ambiente entre os caracteres número de dias para o aparecimento da primeira flor feminina (FF); número de frutos por planta (NF); peso de frutos por planta (PF); cor (CP) e espessura (EP) da polpa; diâmetro longitudinal (DL) e transversal (DT) de frutos; teor de sólidos solúveis (TS); número de sementes (NS) e peso de 100 sementes (PS) por fruto. As populações de melancia B9, 'Charleston Gray', 'Crimson Sweet', 'New H. Midget', M7, P14 e B13, os 21 híbridos F1, em dialelo, e seus recíprocos foram avaliados em campo, de acordo com o delineamento em blocos ao acaso completos, com quatro repetições. Houve grande similaridade entre as estimativas das correlações genotípicas e fenotípicas investigadas. Foram verificadas correlações genotípicas importantes entre os caracteres NF e PF, DL e DT; entre PF e DL, DT, EP e TS e entre CP e FF, EP e TS. Tais correlações indicam que o aumento no número de frutos por planta está correlacionado com a redução do peso de frutos e do tamanho dos frutos (função de DL e DT) e que o aumento no peso dos frutos está associado ao aumento no tamanho dos frutos, da espessura e teor de sólidos solúveis da polpa, assim como a polpa vermelha está relacionada à precocidade e ao aumento na espessura e no teor de sólidos solúveis da polpa. As associações indesejáveis entre os caracteres, como entre número de frutos por planta e cor da polpa e número de frutos por planta e teor de sólidos solúveis, não foram completas, indicando, portanto, a possibilidade de se obter indivíduos recombinantes a partir de populações segregantes sintetizadas através de intercruzamentos de populações contrastantes.

DIFFERENTIAL RESPONSE OF CHEMICALS ON SEX MODIFICATION OF THREE GENERA OF CUCURBITS

Studies on sex-expression and sex-ratio in cucumber, watermelon and bottle gourd were carried out. It was observed that Ethrel at 50 and 100 ppm induced the first pistillate flower earlier and at lower nodes both in cucumber and bottle gourd, whereas, in watermelon, it delayed the appearance of female flowers as compared to the control. Boron 2 ppm proved to be the best for early induction of female flowers in watermelon Ethrel 50 ppm, Ethrel 100 ppm and boron 2 ppm produced the lowest sex ratio in cucumber, bottle gourd and watermelon, respectively. It is evident that the action of sex modifying chemicals differs in the genus citrullus from Cucumis and Legenaria

Effects of β-Ecdysone and Altosid on Flowering, Juvenility and Sex Expression

Summary The effects of both β-ecdysone and altosid upon flowering, juvenility and sex expression are shown. The effect of altosid and β-ecdysone was studied in the long-short day plant Kalanchoe gastonisbonnieri under short days conditions. In this plant GA, substitutes for the long days. The insect hormones had no effect in Kalanchoe . Sex expression was seen in Cucurbita pepo. β -ecdysone did not simulate GA 3 . Altosid slightly delayed the appearance of female flowers. On Coffea arabica cv. Mundo Novo the buds of the plageotropic branches first appear in the 10th leaf pair and then in pairs thereafter. Altosid delayed the appearance of the plageotropic buds.

THE EXPERIMENTAL MODIFICATION OF SEX EXPRESSION IN FLOWERING PLANTS

SUMMARY1. This article summarizes the evidence concerning the modification of sex expression in the sporophytes of flowering plants by external agencies, excluding those which act through genetical paths.2. Three of the primary variables of the plant environment, mineral nutrition, light régime and temperature régime, directly influence sex expression in hermaphrodite, monoecious and dioecious species; their effects, moreover, are reasonably consistent. In general:(a) High levels of nitrogenous nutrition promote femaleness and depress maleness.(b) In short‐day plants and some day‐neutral plants whose development is accelerated by short days, short‐day treatment promotes female and depresses male sex expression. Low levels of light intensity during growth may also inhibit staminal development. In one long‐day plant, spinach, it seems probable that short days lead to the production of male flowers on plants which in normal photoperiod would be phenotypically female.(c) Low temperatures, particularly when experienced through the dark period of a daily photoperiodic cycle, promote female sex expression and depress male.3. Sporophyte sex expression may be modified through certain chemical agencies. In one experiment with Melandrium dioicum, the animal sex hormones have been shown to affect sexuality, oestrone, oestradiol and oestradiolbenzoate promoting the development of pistillate structures in the flower, and testosterone and testosterone propionate of staminate.In monoecious cucurbits, applied auxins simultaneously suppress early flowering, accelerate the appearance of female flowers and increase their over‐all proportion; a‐naphthaleneacetic acid is the most effective auxin in this role. Similar effects are produced in cucumber by exposure to atmospheres containing low percentages of carbon monoxide.Under some circumstances, the general growth‐suppressor maleic hydrazide may differentially inhibit micro‐ and megasporogenesis in hermaphrodite and monoecious species, so altering the functional sex balance.4. Certain forms of mutilation affect sex expression. The reduction of leaf surface and of volume of storage tissue militates against female sex expression in one genus of monoecious aroids. The removal of fruits and female flowers in certain monoecious genera increases the over‐all proportion of female flowers formed. Severe mutilation involving the regeneration of new leading shoots during recovery may lead to later anomalies in sex expression in a number of monoecious and dioecious species.5. In grafting experiments with dioecious species, no authentic cases of the influence of a stock of one sex upon the sexuality of a scion genetically of the other have been recorded.6. The interrelationships of the hypothetical flowering hormone (florigen), auxin and plant sexuality are discussed. In general, photoperiodic treatment which causes early and heavy flowering also promotes female sex expression as against male; also, factors which raise the auxin levels available at the differentiating apex promote femaleness and suppress maleness. These facts appear paradoxical, since, at least in short‐day plants, high auxin levels inhibit the transition from the vegetative to the flowering state. It seems probable, however, that while low auxin levels may be necessary for the initiation of flowering, auxin is necessary for flower development after the formation of the primordia. It may be that in those plants which are accelerated throughout the entire course of flowering by short‐day treatment, such treatment actually increases auxin availability at the apex after the first period of flower initiation.7. A rationalization of two apparently contradictory responses along these lines would permit the formulation of an hypothesis that floral organogenesis is regulated, although not determined, by auxin levels at the apex. Much of the existing evidence would be explained by the assumption that the growth of stamen and pistil primordia is governed by auxin in the characteristic manner, the response following an optimum curve. It seems that the concentration causing maximal stamen growth is lower than that promoting maximal pistil growth, so that auxin level at the differentiating apex determines the sex balance of the flowers produced. In some plants it is probable that this level is susceptible to control in the apex by influences such as temperature, and through the auxin economy of the whole plant, by such factors as nutrition and photoperiodism. It is through these agencies that the sex balance of the flowers may be modified.