Volume 57, Issue 2
February 1963, pages 73-148
pp 73-82 February 1963
The behaviour of the nucleoli from mitotic prophase till the end of telophase is illustrated. Since at prophase, the SAT-threads appear embedded in the nucleolar matrix, their orientation in the mass and the rate of dissolution of the latter would determine whether this relationship would continue till meta- or ana-phase. The persistence of the nucleoli-SAT association often till anaphase indicates that the movement of such nucleoli on the spindle is governed by that of the SAT-chromosomes.
pp 83-87 February 1963
1. Whole worms as well as body wall preparations ofMarphysa gravelyi exhibit spontaneous activity in full strength as well as diluted sea-water.
2. The preparation is very active in sea-water dilutions from 20 to 50%.
3. In Na+, K+, Ca+ free sea-water activity is present. In Mg+ free seawater, the preparation appears to be completely relaxed.
4. While the whole worms tolerate sea-water dilutions ranging from 20 to 70% the muscle preparation appears to tolerate only from 20 to 50% sea-water.
pp 88-95 February 1963
pp 96-98 February 1963
pp 99-105 February 1963
pp 106-116 February 1963
The effect of culture filtrates ofBipolaris sorokiniana and otherBipolaris species (B. oryzae, B. halodes andB. tetramera) grown in different media, on wheat roots, was studied. High concentrations of culture filtrates inhibited elongation of the root, but dilutions of 1/5 or more stimulated root elongation. The extent of inhibition or stimulation in root growth exhibited by culture filtrates varied with the medium in which the fungus was grown. The effects also varied slightly with different isolates ofB. sorokiniana. It is postulated that the fungus produces both a toxin as well as a growth factor in the culture medium. Very little toxin but more of growth factor was detected in culture filtrates obtained from potato dextrose medium. In contrast, more toxin and less of growth factor was produced in culture filtrates obtained from Richard’s medium, although even in this variations were seen depending on the nitrogen source.
In the presence of the culture filtrates ofB. sorokiniana root-hair formation was completely suppressed up to a dilution of 1/100. Root-hairs developed in higher dilutions of the culture filutrate but their number and length were reduced compared to lower dilutions. Root-hairs were formed when the seedlings were removed from the culture filtrates to Hoagland’s solution, but were produced only in the new region of the root which elongated.
pp 117-123 February 1963
The tetraphyllidean larvae increased in volume, when transferred to dilute sea-water. However there is a decrease in volume in 50% sea-water. The conductivity of the medium shows a slight decrease both in 50% and 25% sea-water, indicating the uptake of salts from the external medium. In 10% sea-water the conductivity of the medium goes up steadily.
pp 124-133 February 1963
The mean glycogen content ofM. fragilis is considerably higher than that of the allied speciesM. striata but is lesser than in the teredines. They derive their glycogen requirements mainly from plankton. The glycogen inM. fragilis is not size-dependent as it is influenced by factors like gonadial activity, composition of nutriments, feeding, etc. The glycogen content is higher in mature and gravid animals than in spent ones and decreases on starvation. An increase of glycogen has been recorded as the forms grow to maturity levels with a decrease in nitrogen content.
pp 134-148 February 1963
Of the four isolates ofF. udum tried against six varieties of pigeon pea for pathogenicity, isolate IV was found to be most virulent and varieties N.P. 24, N.P. 82 and N.P. 15 to be the most, moderately and least susceptible varieties respectively. The earliest symptom in pigeon pea wilt was seen on the 10th day when epinasty of the primary leaves appears. This was followed by other symptoms such as inter-veinal chlorosis, yellowing, loss of turgor, shrivelling up of leaves, culminating in wilting of the whole plant by the 30th day. Inoculated plants showed considerable stunting, reduced leaf growth and poor nodulation. The probable role of volatile substances like ethylene in the wilt syndrome and the possibility of this vascular wilt interfering with the trace element nutrition of the host are discussed.
Study of the spread of the pathogen in the tissues of different varieties indicated that while the fungus colonized the entire length of the main axis of the variety N.P. 24, it failed to spread beyond the root region in N.P. 15. Although the spores ofF. udum enter into the aerial portion of N.P. 15 when introduced into the transpiration stream, they failed to survive. The role of inhibitory substance(s) in the tracheal fluid of N.P. 15 is discussed.