Chlorophyll-deficient Mutant Research Articles

Differential effect of sodium azide on the frequency of radiation-induced chromosome aberrations vs. the frequency of radiation-induced chlorophyll mutations in Hordeum vulgare

A considerable synergistic increase of the frequency of cells carrying chromosome aberrations was observed in seeds of Hordeum vulgare , variety Himalaya, irradiated dry with gamma rays and hydrated in sodium azide solutions buffered at pH 3, 7 and 11. This effect, which was most evident at pH 3, was detected throughout development up to the formation of the male gametophyte. No synergistic increase of the frequency of radiation-induced chlorophyll-deficient mutants was observed. This differential effect of the sodium azide post-irradiation treatment on the frequency of chromosome aberrations vs. the frequency of mutations is attributed to the formation of two kinds of lesions in the genetic material of barley following exposure to gamma rays. One kind of lesion, similar to those leading to point mutations in procaryotes, is reparable at low energy potentials and, thus, its frequency is not affected by the sodium azide treatment. The other kind of lesion is associated with chromosome breaks and its repair is affected by the presence of the enzymatic inhibitor.

INHERITANCE AND ALLELIC RELATIONSHIPS OF SEVEN CHLOROPHYLL-DEFICIENT MUTANTS IN BRASSICA CAMPESTRIS L.

Genetic data on seven chlorophyll-deficient mutants showed that all were independent monogenically-controlled recessive genes. The symbol yg is proposed for these characters with the designation yg-1 to yg-7. The value of these mutants in genetic research and in practical plant breeding problems is discussed.

Effects of hydroxylamine and N-Methyl-N?-Nitro-N-nitrosoguanidine in Mimulus cardinalis (Scrophulariaceae): Survival curves and dominant mutants

The lethal and mutagenic effects of hydroxylamine (HA) and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were investigated in the higher plant Mimulus cardinalis. MNNG was found to be more toxic than HA. The shapes of the survival curves obtained at different concentrations of HA and MNNG are interpreted on the basis of decreased biological activity of the solution to increased age of solution. Based on the appearance of chlorophyll-deficient mutants, MNNG is mutagenic in Mimulus. No albinos were detected in HA treated plants. A total of 67 putative mutants were isolated in the mutation spectra of HA and MNNG treated plants. The frequency of mutants induced by HA and MNNG are different. MNNG is mutagenic at 1/10 the concentration of HA in inducing putative mutations in M 1 plants.

Inheritance of leaf color in Allium fistulosum

The petiole color of Allium fistulosum cultivated in Japan is white. A mutant having red petiole was found in 1963. In the cross between red and white and the reciprocal, the F1 was red, and the F2 and F3 consisted of 3 red: 1 white (Table 1, 2). Red color in F1, F2 and F3 was much paler than that of the parent. C, a basic color gene, R, a gene for production of red pigment, and a few intensifiers are assumed.A low temperature sensitive chlorophyll deficient mutant was found in 1964. This plant developed normally in early stage. When overwintered, yellow leaves appeared. However normal green leaves reappeared during the spring growing season. The physiological mechanism of chlorophyll deficiency induced by low temperature is being studied.

Photosynthetic Studies on a Pea-mutant Deficient in Chlorophyll

A chlorophyll-deficient mutant of pea (Pisum sativum) was found as a spontaneous mutation of the variety Greenfeast. Total chlorophyll of the mutant leaves was about one-half that of normal pea leaves per mg dry weight, and the ratio of chl a:chl b ranged from 10 to 18, compared with 3 for normal pea. In each generation the mutant plants gave rise to normal and mutant plants and lethal plants with yellow leaves.For a normal pea plant, CO(2) uptake was saturated at about 60,000 lux, whereas with mutant leaves, the rate of CO(2) uptake was still increasing at 113,000 lux. At 113,000 lux the mutant and normal leaves showed similar rates of CO(2) fixation per unit area of leaf surface, but on a chlorophyll basis the mutant leaves were twice as active. Hill reaction measurements on isolated chloroplasts also showed that the mutant chloroplasts were saturated at higher intensities than the normal, and that the activity of the mutant was at least double that of the normal on a chlorophyll basis.It is suggested that the photosynthetic units of the mutant chloroplasts contain about half the number of chlorophyll molecules as compared to the normal photosynthetic units.Electron microscopy of leaf sections of normal and mutant leaves showed that the mutant chloroplasts contain fewer lamellae per chloroplast and fewer lamellae per granum. The lethal chloroplasts, which were virtually devoid of chlorophyll, were characterized by an absence of grana.

Male sterility in field beans (Vicia faba L.). I. A male-sterile bean inherited as a Mendelian recessive

1. A male-sterile winter bean, inherited as a simple Mendelian recessive, is described.2. The sterility gene was shown to be expressed in the cytoplasm of eleven inbred lines of English winter beans, two varieties of English spring beans, six varieties of foreign spring beans and three varieties of broad beans (Vicia faba major). It is concluded that these varieties are unlikely to provide a fertility-inducing cytoplasm which would allow the development of a non-restoring pollinator.3. Evidence of linkage between three chlorophyll-deficient mutants and the male sterility locus is given and circumstances are outlined by which a suitable marker gene could be employed to assist in large-scale production of hybrid seed.

Electron Microscope Observation on the Development of Chloroplasts of <i>Avena</i> and Chlorophyll-deficient Mutants

1. Development of Avena chloroplasts in normal, etiolated and chlorophyll-deficient mutant plants, are observed with an electron microscope.2. Normal proplastids in green plants have one or two plastid centers, from which fine double lamellae of about 80A in thickness protrude radially, fused each other at the end and formed a sack-like structure. Then the lamellae arrange parallel through the plastid and form ordered layers composed of the fine lamellae. As the number of lamellae in one layer increases, grana are differentiated within certain areas of these layers. Grana are composed of staks of discs of double membranes (grana-lamellae, each of which is about a 80A in thickness). Each disc is connected with one stroma-lamella of about 300A in thickness which is often resolvable as doublet.3. In etiolated and albino leaves, plastid developments are stopped at certain stages of differentiation, and grana can not be formed. This suggests that these structural blockings may be associated with the failure of chlorophyll synthesis.4. In both pale green mutants, mutant 602-15 which is a hybrid between A. strigosa and A. barbata and mutant 3250 caused by X-ray irradiation, plastids develop and grana differentiate, but plastid development is somewhat different between them. While in the mutant 602-15, the completion of lamellar system is followed by destruction caused by vacuolization, in mutant 3250 arrangement of lamellae is abnormal from the early stages and grana arrange irregularly in direction and in localization in mature chloroplasts.

Notes on chimeras in sweet potatoes.

Further studies on the chimeras appearing in the storage roots, stems and leaves of sweet potatoes were made, and some new data are given in the present paper. Agronomic variety OKINAWA-No.l00. In the ordinary strain of OKINAWA-No.l00, the surface colour of storage roots is light red. From this strain, one storage root that was light yellow on its entire surface appeared by somatic mutation. The storage roots of the next generation propagated by stem cutting from this mutant were not always light yellow, and there appeared often the individuals having storage roots that were light red, light yellow or striped or flecked with both colours, though it seems to be accepted usually that mutant colour may be kept in the next generation thus propagated. In view of the fact observed the following passibilities may be cited regarding the causes of this phenomenon. (1) In the light yellow or light red storage roots, the genes in regard to the colour were unstable in the cells of meristems forming the periblem of atems, so that the next generation of such storage roots is not fixed to their colour. (2) Even if the surface of storage roots is light yellow or red, the genes in the cells of meristems forming the periblem of stems may be different from those of the surface of storage roots, the cells of different kind being distributed as Chimeras in the tissues. So that the stems derived from a single storage root of an uniform colour may form storage roots of different surface colour, according to the genes in the tissues from which the stems were originated. Agronomic variety Gokoku. In a large cultivation of GOKOKU, a chlorophyll deficient mutant was found. This plant had four nodes, and the shoot from the undermost one was provided with normal leaves and stems, while those from the other three had chimeral leaves and stems in white and green or in red and green. Observing this chimeral plant morphologically and historogically, the sectorial, the periclinal and the mericlinal conditions in chimeral consitution were found. In the cultivation of OKlNAWA-No.1OO and GOKOKU and other strains of sweet potatoes, various mutants in the colour and other characters occur quite frequently, so that it is quite necessary to pay precise attention in selecting seed storage roots in order to avoid the deterioration of the strains.