Volume 88, Issue 1
January 1979, pages 1-94
pp 1-11 January 1979
Two American isolates and three Indian isolates ofFusarium vasinfectum representing two strainal groups were studied on their congenial and uncongenial hosts for their pathogenicity andin vivo production of pathogen factors. The Indian isolates produced a characteristic vein clearing symptoms on their congenial hostGossypium arboreum while the American isolates produced yellowing and abscission of the leaves on their congenial hostG. hirsutum. In cross inoculation studies these isolates produced atypical symptoms on their uncongenial hosts. Studies onin vivo production of pectin methyl esterase (PME) showed that this enzyme may have a role in pathogenesis ofG. arboreum but not ofG. hirsutum. However the enzyme polygalacturonase (PG) appears to have role in the pathogenesis ofG. arboreum as well asG. hirsutum. The toxin fusaric acid was found inG. arboreum plants infected by the Indian isolates. No fusaric acid could, however, be detected inG. hirsutum infected by any of the isolates studied. Thus fusaric acid appears to have a role in the selective pathogenicity of the Indian isolates and also its production seems to be selective. The present study indicates that different pathogen factors are involved in the development of different symptoms on the two species of cotton.
pp 13-17 January 1979
The early blight pathogen,Alternaria solani was found to utilise various forms of carbon sourcesviz. mono and disaccharides for its growth and proliferation. Inorganic, organic and ammonical nitrogens were good for optimum mycelial and conidial production. Potassium nitrate and proline supported best growth and sporulation. The presence of proline, tyrosine, glucose, sucrose, fructose and maltose in the healthy leaves and their subsequent disappearance in diseased leaves probably play a key role in creating favourable condition for accelerating pathogenicity in the host tissue.
pp 19-24 January 1979
Downy mildew infected ragi plants exhibits a wide range of symptoms. Histopathological studies of the diseased plant have revealed that the fungus mycelium is present in root, stem, floral parts and seed causing morphological and anatomical changes. The mycelium develops profusely in the sub-stomatal spaces and from this the sporangiophores emerge through the stomata. In the leaf tissue invaded by the fungus, the chloroplasts and leucoplasts are either few or absent. Cells of the mesophyll in the case of the diseased leaves are distorted. Sometimes, the cells of the invaded tissue dissolve and the mycelium or sex organs occupy the space thus created. In the leaf tissue, the intercellular spaces surrounding the vascular sheaths are the primary centres of mycelial development. The sex organs are mostly confined to the vicinity of the vascular bundles. In the infected leaf, very few epidermal hairs are developed.
pp 25-28 January 1979
Isolates ofHelminthosporium oryzae adapted respectively to Blitox-50, Dithane Z-78 and Ceresan wet were tested for their pathogenicity andin vivo tolerance to fungicides. There was some increase in pathogenicity in Blitox-50 tolerant and Dithane Z-78 tolerant isolates ofH. oryzae but a marked decrease in pathogenicity was recorded in Ceresan wet tolerant isolate. Rice seedlings sprayed respectively with Blitox-50, Dithane Z-78 and Ceresan wet and inoculated with the isolates ofH. oryzae tolerant to these fungicides did not show any reduction in leaf infection caused by these fungal isolates indicatingin vivo fungicide tolerance.
pp 29-33 January 1979
The pentosan content of different varieties of finger millet ranged from 2.7 to 4.0%. The total carbohydrate content of the pentosan preparations ranged from 52 to 92% and protein content varied from 3.9 to 18.1%. The water-soluble and alkali-soluble pentosans of two varieties of finger millet contained the sugars glucose, arabinose and xylose. Galactose, which is commonly found in some cereal pentosans, was not present.
pp 35-48 January 1979
Dillenia indica Linn, is widely used in the indigenous systems of medicine; the leaf and bark as an astringent, the bruised bark, externally as a cataplasm in arthritis, and the fruit juice as a cough mixture, a cooling beverage as also for toning up the nervous system. It is considered a ‘vat’ suppressant ‘pitta’ augmenting drug in Ayurveda. The paper deals with pharmacognosy of the leaf ofD. indica. The characters studied in detail include both macroscopic and microscopic characters; physical and other constants, such as stomatal index, palisade ratio, vein islet numbers, vein termination numbers, ash values, percentages of tannins, total sugars and reducing sugars. Preliminary phytochemical tests, TLC and fluorescence tests have also been carried out.
pp 49-56 January 1979
Pollen morphology was studied in 33 collections belonging to 26 species, using the acetolysis technique. The pollens were mainly 3-zonocolporate, rarely 2-zonocolporate. Exine surface had varying degrees of reticulation. The os (endocolpium) was mainly lalongate, but rarely lolongate. Variations in pollen size were also observed and sometimes micropollens were observed. The pollen could be prolate, sub prolate or spheroidal in shape. The details of pollen morphology are discussed in the light of earlier reports in the genus and it is emphasised that the genus is fairly homogeneous in pollen morphology.
pp 57-61 January 1979
The floral anatomy ofGrewia tenax (Forsk) Fiori reveals that the sepal-petal-stamen traces emerge as composite strands from the main stele. The glandular corana is present at the base of each petal. The stamens show the obdiplostemonous condition. Due to chorosis the number of stamens reaches upto 50. The placentation is interpreted as parietal derived from the axile one.
pp 63-67 January 1979
The floral anatomy ofTrichopus zeylanicus Gaertn. is described in detail. The inferior ovary is considered to be an appendicular structure. The union of the filaments with the style to develop a short column and the vascular supply to the tepals are considered as important features in support of the separate treatment ofTrichopus. Both the perianth whorls are anatomically similar and are best described as tepals.
pp 69-73 January 1979
An experiment was conducted to study the influence of phorate (0, 0-diethyl-S-thiomethylphospherothiol-thionate, Thimet 10G‡) at 1·25 kg/ha, alone and in combination with Fe-EDTA (4 ppm Fe) on the fresh weight, dry weight and per cent N, P, K, Ca, Mg and Fe content of the leaf, stem and fruit portions of okra plant as well as the seed yield. Phorate alone and in combination with Fe-EDTA increased both fresh and dry weights of leaves, stem and fruits per plant and seed yield per hectare in comparison to control, FeSO4, EDTA and Fe-EDTA. Phorate treated plants also had higher N, P and K in fruits ‚stem and leaves respectively. When combined with Fe-EDTA it increased Fe content of the leaves. It is concluded that phorate action neither involves Fe-chelation nor greater mobilization of Fe in the plants.
pp 75-77 January 1979
The results demonstrate that the susceptibility ofCapsicum pendulum to potato virus X varies with the time of inoculation and this in turn is influenced both by pre- and post-inoculation light conditions. Darkness subsequent to inoculation inhibits the development of local lesions whereas continuous light stimulates it.
pp 79-86 January 1979
A comparative study was made of the meiotic behaviour and protein electrophoretic patterns of 12 different varieties of barley (Hordeum vulgare L)., including chiasma frequency, pollen sterility and chromosomal behaviour during different stages of meiosis. Though all the cultivars showed a uniform somatic chromosome number of 2n = 14, they differed from each other in details of meiotic behaviour. Proteins were extracted from the seeds and subjected to polyacrylamide gel electro-phoresis. Within a certain range, each variety showed a distinct pattern.
pp 87-94 January 1979
Morphology of the seeds and seedlings ofEuphorbia hirta andE. thymifolia are described. In both the species, the seeds are endospermous, exotegmic, more or less oblong and obtusely tetragonal. The testa is only two-layer thick, collapsing when dry; the tegmen is made up of a single layer of macrosclereids with occluded lumen. The early developmental pattern of the seedlings in both the species is the same. The first internode is condensed and the first pair of leaves develop in a decussate fashion to the cotyledonary leaves. Early in the development of young seedlings, 4–5 extra-axillary branches originate at the first leafy node. These branches inE. thymifolia lead to the rosette form of mature plant whereas inE. hirta these branches are eliminated and an erect plant is the result and branches from the main axis develop only subsequently. The nature of the seedlings are correlated with the ecology of the plants.