Proline Accumulation and Varietal Adaptability to Drought in Barley: a Potential Metabolic Measure of Drought Resistance

A reliable laboratory test for drought resistance in crops would be invaluable in breeding programmes. Experience so far has been disappointing, however, due to either a lack of differentiation between genotypes¹, or poor correlation between the results of the test and field experience^2–4.     

A Biochemical Study of Spore Germination in the Blue-green Alga Anabaena doliolum

The spores of Anabaena doliolum formed in light (light spores)and after transfer to darkness (dark spores) are biochemicallydifferent in that the light spores contain chlorophyll a andphycocyanin, while dark spores seem to lack them. The apparentbiosyntheses accompanying dark-spore germination seem to proceedin the following order: RNA, chlorophyll a, phycocyanin andDNA. Results of chloramphenicol treatment indicate that proteinsynthesis precedes RNA synthesis. The biosynthetic events followingRNA synthesis show a requirement for light.     

Screening of Genotypes of Brassica juncea L. for Leaf Conductance under Field Conditions

Twenty-three genotypes of Indian mustard were studied for leafconductance (K₁) at the floral bud initiation stage under non-stressconditions. The comparison of leaf conductance and of severalother measurements in the standard cultivar ‘Prakash’demonstrated that a screening procedure could be developed forleaf conductance prior to the flowering stage of mustard grownin the field. Errors due to short term environmental fluctuationsand to ontogenetic drift in conductance can be reduced if themeasurements are made on both the ad- and abaxial surfaces ofthe uppermost expanded leaf between 1200 h and 1400 h on cleardays. Irradiance levels can be neglected once a value of photosyntheticallyactive radiation (PAR) of about 1000 µE m^–2 s^–1at the adaxial surface or of 1200 µE m^–2 s^–1at the crop canopy has been reached. The water status of theplants is of no importance as long as the plants are not underundue stress. The different genotypes showed a genetic variabilityof 243% in leaf conductance.     

Effect of Light, Temperature and Substrate during Spore Formation on the Germinability of Conidia of Colletotrichum falcatum

This paper presents results on the effect of light, temperature and substrate during spore formation on the germinability of conidia in Colletotrichum falcatum. Light seems to have no effect on the germination of conidia unless the cultures were exposed to a high intensity of light during sporulation, in which case the spores showed a reduced germination and an increased appressoria formation. Conidia produced at temperatures higher than the optimum showed better germination and less appressoria formation than the spores produced at the temperature optimum for the growth and sporulation of the fungus. A similar increase in germination was also observed in conidia obtained from inoculated sugarcane leaves as compared to those produced on culture media. The light type virulent isolates of C. falcatum showed greater sensitivity to all these treatments than the dark type weakly pathogenic isolates.     

Floral development of Iris decora Wall. (Iridaceae)

The outer tepal and stamen primordia arise as secondary primordia on the outer tepal-stamenprimordia, which are formed on the floral apex. The inner tepal primordia are formed directly on the floral apex. All the floral appendages are initiated in the second tunica layer and are homologous with regard to their origin and early development. A short perianth tube is formed as a result of intercalary growth in the common bases of the tepal primordia. The intercalary growth in the fused bases of the floral appendages elevates the peripheral zone. The floral apex thus appears as a shallow cup. Further intercalary growth results in the formation of an inferior ovary. The ovules are initiated as outgrowths on placental ridges from the lateral ovary wall, the trilocular appearance being the result of secondary cohesion of the parietal placentae.     

Modification of growth, yield and lodging response of lentil to phosphorus by paclobutrazol

A foliar application of paclobutrazol (1 litre a.i. ha“¹) was applied before flowering of lentils grown with different levels of phosphorus (0, 20, 40, 60, 80 and 100 kg P₂0₅ ha”¹). Increasing amounts of P up to 80 kg ha“¹ increased plant height, crop dry matter and grain yields but also increased crop lodging. Paclobutrazol decreased plant height and lodging and increased grain yield. Maximum yields were obtained with a combination of 80 kg P ha”¹ and paclobutrazol.     

The Lobster Parasite Anophryoides haemophila (Scuticociliatida: Orchitophryidae): Nuclear 18S rDNA Sequence, Phylogeny and Detection Using Oligonucleotide Primers

ABSTRACT. We have determined the nucleotide sequence of the nuclear gene encoding small-subunit ribosomal ribonucleic acid of the ciliate Anophryoides haemophila , a parasite of the American lobster Homarus americanus. The gene is 1763 bp in length, and has a guanosine-plus-cytosine content of 43.9%. Inferred phylogenetic frameworks strongly support the monophyly of the scuticociliates, and suggest that order Scuticociliatida should be elevated to at least subclass rank. Oligonucleotide probes based on A. haemophila ssu-rDNA can discriminate between DNAs of A. haemophila and other investigated hymenostome ciliates, and effectively prime polymerase chain reaction-based detection of A. haemophila deoxyribonucleic acid against at least a 1600-fold excess of total deoxyribonucleic acid from H. americanus.     

Effect of cytokinins supplied via the xylem at multiples of endogenous concentrations on transpiration and senescence in derooted seedlings of oat and wheat

This study was conducted lo determine whether naturally occurring xylem cytokinins, when supplied to leaves via the xylem at approximately endogenous concentrations, increase transpiration and delay senescence in selected monocot species (oat and wheat). The concentrations of some of the major cytokinins (zeatin, dihydrozeatin, ciszeatin and their ribosides, the O-glucosides and nucleotides) were determined in the xylem exudate of oat and wheat seedlings by radioimmunoassay. Evidence is presented that the small volume of exudate (4–5 mm³) collected per plant was xylem sap in transit at the time of shoot excision. Using the data on cytokinin levels, the individual bases and ribosides (and a base/riboside mixture), at multiples of concentrations determined in xylem sap, were tested in transpiration and senescence bioassays. The individual O-glucosides (and mixtures of the O-glucosides) were similarly tested at (i) multiples of the molar concentrations of the corresponding bases and ribosides, and/or at (ii) multiples of the endogenous concentrations. Similarly, zeatin and dihydrozeatin nucleotides were tested at multiples of the molar concentration of zeatin riboside and, in some instances, at multiples of endogenous concentrations. Our results suggest that, at least in oat and possibly in wheat, zeatin-type bases, ribosides and O-glucosides supplied to the leaf in xylem sap are likely to play a role in regulating transpiration in vivo. O-glucosides in oat xylem sap may be important regulators of leaf senescence in the intact plant. The nucleotides were present in xylem sap at lower concentrations than most of the bases, ribosides and O-glucosides. The nucleotides appear likely to play a lesser role than the bases, riboside and O-glucosidcs in controlling transpiration and senescence in the intact plant.     

Differentiation of freezing tolerance and vernalization responses in Cruciferae exposed to a low temperature

High levels of freezing tolerance were induced in leaves of different Cruciferae species including Brassica napus, Arabidopsis thaliana, Barbarea vulgaris, Thlaspi arvenses and Descurainia sophia by low-temperature acclimation. Concomitantly, the amount of total RNA doubled in these three species. Analyses of methylation patterns and dosage of rRNA genes were carried out to determine whether or not alterations occur in this DNA during development of freezing tolerance. Hybridizations of Southern transfers with an rDNA probe revealed two additional EcoRI sites in purified DNA isolated from freezing-tolerant leaves of winter B. napus cv Jet Neuf and D. sophia (both of which require low temperatures for vernalization), but not in isolates of A. thaliana or spring B. napus cv Topas. An increase of rDNA cistrons was also observed in both B. napus cv Jet Neuf and D. sophia but not in A. thaliana or B. napus cv Topas upon cold acclimation. These results suggest that low temperature induced amplification of rDNA and the differential methylation of EcoRI sites may possibly be related to the vernalization process but may not be related to the development of freezing tolerance. However, the higher activity of RNA polymerase (2.5 times more) observed upon cold acclimation may explain the concomitant increase in total RNA and may be related to the development of freezing tolerance in the Cruciferae.     

Ioral organogenesis of Echinodorus nazonicus Rataj and floral construction f the Alismatales

The primary trimerous pattern of the flower of Echinodorus amazonicus Rataj is clearly exhibited in the earliest developmental stages. After the inception of three sepals, theree alternisepalous petal-stamen complexes arise, each of which, at successively higher levels of the primordia, consists of a petal, a pair of stamens, and a single stamen. In alternation with these three petal-stamen complexes three groups of three pistil (carpel) primordia are formed. Subsequent pistil primordia are formed rapidly in alternation with the preceding ones. Teratological buds were observed in which one pistil primordium appeared to be replaced by a normal stamen primordium. General features of the flowers of the Alismatales are summarized in developmental fashion which includes the mature flower as a final stage. With the exception of Limnocharis and probably Wisneria , all alismatalean flowers appear to be characterized by antipetalous stamen (or staminodial) paris. In members studied thus far, the basic trimery differs radically from that found in certain taxa of the Magnoliidae.