Volume 91, Issue 4
August 1982, pages 281-370
pp 281-287 August 1982
Anatomy of the juvenile nodes in the seedling of fourteen genera of Leguminosae is described. The cotyledonary node exhibits a two-trace, unilacunar condition. The two traces show various degrees of approximation of the two traces leading to one-trace, unilacunar condition in some genera. At the second node level, only two genera show the one-trace, unilacunar pattern; 11 of the remaining genera have a three-trace trilacunar supply and one genus exhibits an intermediate type. At the third node level all the genera show a three-trace, trilacunar pattern. The present data suggest that the three-trace, trilacunar condition is derived by the addition of a lateral trace on either side of the median trace and that the one-trace, unilacunar condition appears to be a result of the approximation of the two traces at the cotyledonary node.
pp 289-295 August 1982
Four different types of cork-warts, the ordinary cork-warts, the d-scars, wound cork and trichome scars have been described fromE. citriodora andE. torellina. The differences between them are discussed.
pp 297-301 August 1982
Structure, ontogeny and distribution of sclereids in the pericarp of seven species of mimosaceae are studied. Their occurrence is recorded in the epidermis hypodermis, mesocarp and endocarp. They may be macrosclereids or brachysclereids. Their structure and ontogeny are described and their taxonomic utility is pointed out.
pp 303-308 August 1982
In the present study an attempt has been made to establish the fate of sporangia ofSclerospora graminicola (Sacc.) Schroet deposited in the soil. A technique has been standardised to demonstrate the germination of sporangia and the viability and infectivity of zoospores in the soil under laboratory conditions. For how long the zoospores remain motile in the soil is one of the many unanswered questions in the zoospore biology. From the present study it is seen that, the sporangia can germinate in the soil and liberate zoospores. The zoospores can move against gravity, remain viable and infective for 5 hrs in the soil. Survival of zoospores in the soil indicated that, they may serve as a potential secondary source of inoculum through soil under field conditions.
pp 309-318 August 1982
Initiation and development of root nodules are studied in 7 species and the structure in 4 species, belonging to 3 genera of the tribe Trifolieae. The shape of the mature nodules may be spherical, cylindrical, fan-like or coral-like. The bacterial threads enter the root through the intact epidermis and cause proliferation in cortex by liberating the bacteria. The origin of nodules in the investigated taxa is exogenous and they belong to the «apical» type in Kodama’s classification. A mature nodule comprises of meristematic zone, cortex with vascular bundles and the bacteroid zone. The bacteroid zone is heterogeneous and is composed of infected and uninfected cells.
pp 319-328 August 1982
The heterostylous taxonT. ulmifolia var.elegans Urb. (2n=20) and the homostylous taxonT. ulmifolia var.angustifolia Willd. (2n=30) were selfed and intercrossed. Both pin and thrum forms of var.elegans are self incompatible while the varietyangustifolia is self compatible. Among the intervarietal combinations onlyangustifolia × elegans (thrum) crosses were successful though the hybrid seeds were inviable.
From an analysis of the results ofin vivo pollen germination studies in the incornpatible crosses, it is concluded thatangustifolia pollen are of the thrum type and its pistil is of the pin type. It is suggested that var.angustifolia has evolved by a rare crossing over within the super gene complex for heterostyly in the parent taxon, which might be the hexaploid (2n=30) heterostylousT. ulmifolia Linn. The failure of the apparently «legitimate» crosselegans (pin) ×angustifolia is suggested to be due to the ploidy difference between the two varieties. On morphological cytological and biochemical grounds the separation of theelegans element from,T. ulmifolia complex and assigning of species status to it is suggested.
pp 329-350 August 1982
Field assessments at regular intervals from April 1975 to March 1979 recorded 61 plant species comprising 13 grasses, 20 weeds and 28 trees and shrubs as emitting appreciable amounts of pollen into the atmosphere of Visakhapatnam. The data also showed relative prevalence of these taxa in different zones of the city and their flowering periods. Pollen output in terms of number per anther and per flower was determined for 29 taxa. Air sampling with rod traps of 0·53 cm diameter enabled the identification of 23 different pollen types in the atmosphere with Poaceae accounting for Ca. 37% of the total pollen load.Casuarina contributed to 13% followed by Cyperaceae 6%,Eucalyptus 5·8%,Dodonaea 3·8%, Amaranth-Chenopod andPhoenix each 3·4%,Borassus 2·4% andPeltophorum 2%. Of the total identified pollen, ca 85% belonged to anemophilous taxa. There was no pollen-free day. The total pollen and individual types displayed seasonality quite closely corresponding with the blooming seasons of the source plants. Three pollen peaks, two in the wet period (June–November) and one in the dry period (December–May) were evident. Year to year variations in pollen abundance occurred and urban growth affected pollen frequency pointing to the need for routine monitoring of the atmosphere.
pp 351-356 August 1982
The floral anatomy ofKniphofia uvaria Hook. is described. The tepals are anatomically similar and one-traced. The stamens are one-traced. The outer whorl consists of shorter stamens. The placentation is parietal, nectary ovarian and septal. The extension of the carpellary ventrals into the style is an important anatomical feature. The trend towards development of an inferior ovary is noted. Evidence from floral morphology and other disciplines is discussed and it is inferred that the alleged affinity ofKniphofia and the Kniphofieae with the Aloineae and the Hemerocallideae is rather remote.
pp 357-370 August 1982
Macrophomina phaseolina is a serious pathogen which is externally as well as internally seed-borne. It causes failure of seed germination and browning and rotting of seedlings. The presence of pathogen in infected and healthy looking seedlings was tested by clearing, sectioning and incubation techniques. After 8 weeks almost every surviving plant developed pale yellow to brown circular or oval concentric spots on leaves, stem and capsules. Mycelium and microsclerotia were observed in the peripheral region of the lesions. Splitted root, stem and capsule also showed the presence of microsclerotia. Cleared wholemounts of leaf and stem and T.S. and L.S. of stem showed inter- and intracellular mycelium in cortex, xylem and pith cells. Microsclerotia were also observed. In capsule, infection was recorded on its inner wall, septum, placenta and seeds spreading from base to apex.