Measurement of the Water Potential of Intact Plant Tissues1

A modified design of a thermocouple psychrometer is describedwhich utilizes the Peltier effect for producing an exceedinglysmall wet-bulb thermometer. The thermocouple assembly has beenreduced to miniature dimensions and the thermocouple chamberconsists of a silver cylinder (volume 0.06 cm³) whose base isformed by the material under observation. This makes it possibleto measure water potentials over limited surfaces of intactplant tissues, e.g. germinating pea seeds (Pisum sativum L.).The apparatus is capable of measuring water potentials downto a magnitude of about –6,000 joules/kg.³     

Effect of Nitrogen on Nitrate Reductase Activity in the Nodules and Leaves of Summer Moong (Vigna radiata)

The relation of the in vivo nitrate reductase (NR) activityto growth period was studied in the nodules and the leaves ofthe summer moong (Vigna radiata). The maximum NR activity wasobserved 31 days after sowing (DAS) in the leaves and 28 DASin the case of the nodules. In a pot experiment, the effectof the various nitrogen concentrations, namely 0, 3, 6, 9 and12 mg kg^–1 was studied on NR activity at three growthstages. The maximum NR activity was observed at 6 mg kg^–1N during the pre-flowering stage (26 DAS). Though the noduleshave higher NR activity, its expression was limited by substrateavailability. The NR activity in the leaf could be used as anindex of NR activity in the nodules. Nitrate reductase, nitrogen, nitrate, moong, Vigna radiata     

A new species of Porina from the Andaman Islands,India

A new species of foliicolous lichens, Porina andamanensis, from the Andaman Islands, India, is described and illustrated.     

Secondarily-forming Coated Vesicles in Ray Parenchyma Cells of Pinus radiata Needle Traces

Coated vesicles in ray parenchyma cells of Pinus radiata needletraces were observed to form secondarily from smooth vesicles.The nascent coated vesicles were seen as small protrusions ofthe bounding membrane of smooth vesicles. Initially they wereellipsoidal or dome shaped, later becoming spheroidal. Althougha coat was observable at the spheroidal stage the coat was mostpronounced in vesicles that had separated from parent smoothvesicles. Coated vesicles were most common near dictyosomeswhere they were often seen in stages of formation from smoothvesicles and in the cortical cytoplasm near the plasmalemma.The plasmalemma developed small protrusions some of which appearedcoated at the cytoplasmic face. Coated vesicles, Pinus radiata, needle trace, ray parenchyma     

Efficacy of carboxin and heat treatment for controlling the growth of Sclerotium rolfsii during culture of the mushroom Pleurotus flabellatus

Soaking paddy straw for 18 h in a carboxin suspension in water (5 mg a.i./l) effectively controlled the growth of Sclerotium rolfsii occurring as a natural contaminant in paddy straw, during culture of the mushroom Pleurotus flabellatus. Carboxin at this concentration delayed sporophore formation by 2–3 days, but did not affect total yield. No detectable carboxin residues were found in the mushrooms grown on the treated paddy straw. Treatment of the paddy straw with hot water at 60°C for 10 min completely controlled the contaminant without affecting mushroom growth and yield; but 20 mm treatments with hot air at 60°C or heating with the steam to 75–80°C did not control S. rolfsii.     

Mating Systems and Distribution in some Tropical Ferns

Applying mating system genetics as the tool, three tropicalferns, namely, Ceratopteris thalictroides, Pseudodrynaria coronansand Pityrogramma calomelanos were examined for their distributionalpatterns. Absence of recessive lethals in the sporophytes ofP. colomelanos allows its spores to function as a single propagulein the colonization of open habitats through intra-gametophyticselfing and it is widely distributed. The phenomenon of leakylethality and ultimately recessive sporophytic lethality inP. coronans is associated with a restricted distribution ofthe species in the forest. Ecological specialization in thecase of C. thalictroides also renders it a poor colonizer thoughits mating system is directed towards intergemetophytic selfingwith capacity in time for intra-gametophytic selfing.     

Synergistic Action of Particulate and Gaseous Pollutants on the Growth of Triticum aestivum L.

Wheat plants raised in 1 m² plots were treated with cement andnitrogen dioxide (NO₂) alone and in combination between theages of 20 and 100 d. The plant samples, collected at certainintervals in their growth period, were analysed for chlorophyllconcentration and rate of production. The grain samples collectedat the end were analysed for certain characteristics. The resultsreveal that cement dust and NO₂ applied alone and in combinationon plants caused a measurable reduction in chlorophyll contentand biomass accumulation. It was seen that the effects of combinedcement + NO₂ treatment of plants were less than the summed effectsof individual pollutants. However, initial fumigation of plantswith NO₂ induced the synthesis of chlorophyll, giving a darkerappearance to fumigated leaves. As compared to controls, thegrains treated with either pollutants or both showed quantitativeand qualitative deterioration except a slight increase in proteincontent of NO₂-treated grains.     

In Vivo Fixation of CO2 by Attached Pods of Brassica campestris L.

In vivo net CO₂ exchange characteristics of attached Brassicapods were studied during the entire period of their growth anddevelopment after anthesis. ¹⁴CO₂ was fed both from the externalatmosphere and internally through the pod cavity, and the anatomyof the pod-wall was examined microscopically. Stomata were observedin the outer epidermal layer of the pod wall. Net in vivo CO₂fixation by the pods was observed throughout the period of theirdevelopment and was maximum on day 42 after anthesis (DAA).Compared to the internal feeding experiments, ¹⁴CO₂ fixationfrom the external environment was very high. Apparent translocationof fixed carbon from the pod wall to seeds was rapid. Pod photosynthesiscontributed substantially to seed growth. pods, Brassica campestris L, CO₂ fixation, stomata     

Nitrate Reductase Activity: A Biochemical Criterion of Hybrid Vigour in Sorghum bicolor (L.) Moench

F₁ hybrids of Sorghum bicolor (L.) Moench and their inbred parentswere analysed for NADH-nitrate reductase activity during theearly stages of seedling growth. In all the hybrids both mid-parentaland better parental heterosis were discernible in shoots whereasin roots two hybrids out of the three tested, showed heteroticlevels. It is suggested that in sorghum nitrate reductase activityduring seedling stages can be used as a biochemical criterionfor evaluating hybrid vigour. Sorghum bicolor (L.) Moench, sorghum, hybrid vigour, nitrate reductase