Growth and biometric relationships of the pearl oyster Pinctada fucata (Gould) on transplanting from the Gulf of Mannar to the Arabian Sea

Comparative studies were made on the growth and biometric relationships of the pearl oyster Pinctada fucata (Gould) Tuticorin stock at (Tuticorin (TST) – parent stock) transplanted from the Tuticorin Bay (8.7°N; 78.2°E) in the Gulf of Mannar along the Indian southeast coast to Kollam Bay (8.8°N; 76.5°E) in the Arabian Sea along the Indian southwest coast (Tuticorin stock at Kollam (TSK) – transplanted stock). At the time of transplantation, Kollam Bay did not have a native stock, however, within a year, the transplanted stock spawned and oyster spats were collected from within the farm (Kollam stock (KS) – progeny stock). The growth in dorso‐ventral measurement and total weight in Kollam Bay was 1.4–1.6 times and 3.1 to 6.8 times respectively greater than that observed at Tuticorin. Furthermore, at Kollam Bay, the thickness observed at the end of first year was similar to that obtained at the end of second year in Tuticorin. Both the TSK and KS had significantly higher instantaneous growth rates (IGR) than TST. All the stocks displayed significantly different biometric relationships. The increased growth in Kollam Bay is attributed to the almost double productivity in the Arabian Sea compared with the Bay of Bengal. It is concluded that in the case of P. fucata, the site and its interaction with environment are important determinants of growth and shell dimensions. The present study clearly indicates that the environmental conditions prevailing along the southeast Arabian Sea are congenial for the growth, gametogenesis, spawning and settlement of P. fucata larvae. In spite of strong monsoonal influences in the hydrology of Kollam Bay, the growth and reproduction of P. fucata stocks indicates its relative hardiness and ability to adapt to a changed environment.     

Antifeedant activity of vicolides from Pentanema indicum

Vicolides A–D (0.2–2000 ppm) from Pentanema indicum showed antifeedant activity against Euproctes fraterna and Pericallia ricini V stage larvae.     

Evaluation of salt tolerance in cowpea and tobacco: Effects of NaCl on growth,relative turgidity and photosynthesis

The physiology of NaCl induced stress was studied in two prop species, cowpea and 4 cultivars of tobacco one of which (Jayashree) is salt sensitive. It was found that the growth of all the cvs of tobacco was reduced by the presence of NaCl (100 mH) in the nutrient medium. While the fresh wt per unit area of the leaves of salt‐tolerant tobacco cv. I and PV‐7 (Nicotiana tabacum L.) and MPS‐219 (N. rustica L.) was increased’ significantly, it was decreased in the salt‐sensitive Jayashree. The dry wt per unit leaf area was decreased much more in I, PV‐7 and J than in NPS‐219. The total chlorophyll was reduced in all and more so in Jayashree.

The relative turgidity % was found to decrease in the primary leaves of cowpea (Vigna unguiculata L.) in the first 6 days of treatment with 100 mM NaCl in the nutrient medium while the decrease was less significant in the first and and second trifoliate leaves, showing that there was readjustment with growth of the plant to salinity. The ¹⁴C fixation in the leaf disks of cowpea grown in NaCl was much less than in the control plants. The studies reveal that there is a general reduction in the growth of both tobacco and cowpea following NaCl treatment and this effect is due to a decrease in the total chlorophyll and a reduced rate of photosynthesis.     

An examination of Fe deficiency stress response in relation to Fe uptake in two sorghum hybrids and their parent cultivars

Two sorghum (Sorghum bicolor L. Moench) hybrids CSH‐10 and ‐ 11 and their parent cultivars 296‐A, SB‐1055 and MR‐715 were examined for their tolerance to Fe‐deficiency stress, and also Fe uptake. It was observed that there was greater reduction of pH of the nutrient media and more rapid recovery from chlorosis only in the female parent 296‐A, and to some degree in the hybrids, but not in the male parents. The results indicated that Fe uptake‐translocation were inversely related to their Fe stress tolerance.     

Molybdenum Uptake and Nitrate Reductase Activity in Sorghum (Sorghum bicolor L. Moench). Evidence for Heterosis

The absorption of Mo by the roots and. transport to the shoot of intact seedlings of a sorghum hybrid and its parent cultivars were measured for 3 h from 10 to 100 μmol ammonium molybdate. The patterns of absorption revealed hybrid vigour and the hybrid followed the patterns of the male- parent 168. Studies on the effects of different amounts of Mo on the nitrate reductase activity also showed the occurrence of hybrid vigour in the- hybrid CSH-7.     

Excretion of dibutyl phthalate by sorghum roots under Fe‐stress: Evidence of its action on chlorosis recovery

Sorghum (Sorghum bicolor L. Moench) cv. CSH‐7, an Fe‐efficient hybrid was grown and subjected to Fe‐deficiency stress. The nutrient medium was extracted for isolation of reductant chemicals. By means of thin layer chromatography, I.R. spectrum and HPLC analysis, dibutyl phthalate was identified as the principal component. This chemical was not found in the nutrient medium extracted before the onset of chlorosis or in that after the plants recovered from chlorosis. Furthermore, synthetic dibutyl phthalate and that obtained from the exudate when supplied to the nutrient medium caused greening of chlorotic sorghum in 24 hours. Evidence that the root medium of the Fe‐efficient sorghum can induce recovery of an Fe‐inefficient sorghum grown together, has also been obtained. It is concluded that dibutyl phthalate released by the Fe‐efficient sorghum subjected to stress, is responsible for making Fe available for utilisation. The mechanism of action of dibutyl phthalate on chlorosis recovery is still an open question.     

Identification of dibutyl phthalate in the root exudate of Fe‐efficient (corchorus capsularis L.) subjected to Fe‐deficiency stress : Its action on Fe‐chlorosis recovery

The jute (Corchorus capsularis L.) cv. 3RC‐212 which is Fe‐efficient, was subjected to Fe‐deficiency stress, and the nutrient medium was examined for chemicals, when the plants became chlorotic and the pH was lowered to about 4. While phenolic acids could not be detected, DBP (dibutyl phthalate) was identified in the extract by means of TLC and HPLC. The effect of DBP and caffeic acid was studied in JRC‐212 and DBP was found to cause recovery of the plants from chlorosis in 5 days. The chemicals, PA (phthalic acid), a derivative of DBP (50 mg/1) were supplied to chlorotic plants of JRO‐632, an Fe‐inefficient jute cultivar, and both the chemicals were effective in chlorosis recovery. PA application caused more rapid greening than DBP.

Jute is the second crop species in which DBP is identified in the root exudate. The detection of DBP was first recorded in sorghum CSH‐7.     

Absorption and transport of Na and Cl in rice cultivars differing in their tolerance to salinity: An examination of the effects of ammonium and potassium salts

The absorption and transport of Na and Cl from 0.1 mM and 10 mM ²²Na labelled NaCl or ³⁶Cl labelled KCl were examined in 15 days old seedlings of 3 cultivars of rice differing in their tolerance to salinity. Furthermore, the effects of 10, 100 and 1000 ppm (N)₂S on their uptake were studied. It was found that in general, the salt‐tolerant cultivars BR and PNL‐1 absorbed more Na and translocated a lesser proportion of it to the shoot, compared to the salt‐sensitive IR‐8, from 0.1 mM NaCl. The presence of (N)₂S reduced the uptake of Na in all the cultivars. It was also found that the presence of 100 ppm K, KN or NNreduced Na absorption from 0.1 mM NaCl significantly in all the cultivars, and the translocation to shoot in BR‐ Chloride transport from 0.1 mM NaCl was reduced by (N)₂S in all the cultivars. The 3 cultivars differed significantly in the rates of absorption and transport of Na and Cl. The results indicate that PNL‐1 which is a cross of IR‐8 X BR, has inherited the salt tolerance trait from BR. Lower rates of Na translocation to the shoot can be used as an index of salt tolerance in rice.     

Differential zinc uptake and transport in sorghum varieties suited for different moisture regimes

Zinc absorption and transport were examined in M‐35 a drought resistant, and M‐47, a drought susceptible sorghum (Sorghum bicolor L. Moench) cultivar. Excised roots were employed to study the mechanisms of uptake at cellular level in these varieties.

The absorption over 0 to 130 μM ZnCl₂ followed a biphasic pattern with a second rise at 90 μM, a feature which was not observed in the absorption by roots of intact seedlings. While there were no differences in the patterns of absorption in the two cultivars, the transport to shoot in M‐35 followed a slower rate up to 90 μM than that in M‐47. When Zn uptake was examined for 6 hours, the absorption and transport showed a number of changes in phase, which were running parallel. The transport of Zn followed a higher rate in M‐47 than that in M‐35.

Phosphate decreased the uptake and also transport of Zn in both the varieties. However, Zn inhibited phosphate absorption and transport in intact seedlings differentially amongst the varieties. Further, the inhibition of Zn uptake was much less in M‐35 than in M‐47, a feature which will perhaps facilitate survival of M‐35 under water stress, a condition which would also limit phosphate availability.