- [Show abstract] [Hide abstract] ABSTRACT: The effect of four phosphate-solubilizing bacteria (PSB), (Burkholderia gladioli 10216, Burkholderia gladioli 10217, Enterobacter aerogenes 10208 and Serratia marcescens 10238) as identified on the basis of 16S rRNA gene sequencing was evaluated on plant growth and commercially important glycosides, stevioside (ST) and rebaudioside-A (R-A) of Stevia rebaudiana in pots containing tricalcium phosphate (TCP) supplemented soil. The PSB were isolated from the rhizosphere of S. rebaudiana plants and tested for P-solubilization ability, biocompatibility, indole acetic acid (IAA) and siderophore production. In greenhouse study, treatment of either individual PSB or a consortium (of PSB) resulted in increased plant growth. ST and R-A contents. The stimulatory effect was observed with consortium treatment in plant growth parameters (shoot length, 22.5%; root length, 14.7%; leaf dry weight, 89.0%; stem dry weight, 76.3% and shoot biomass, 82.5%) and glycoside contents (ST, 150% plant(-1) and R-A, 555% plant(-1)) as compared to the un-inoculated plants. Among individual PSB treatments, B. gladioli 10216 showed most promising response in majority of the parameters studied. The root colonization potential of PSB, assayed by RAPD technique, showed the colonization of all PSB isolates, though their extent of colonization varied.
- [Show abstract] [Hide abstract] ABSTRACT: It was observed that the unpollinated flowers of Cymbidium pendulum (Roxb.) Sw. and C. aloifolium (L.) Sw. stayed fresh for 20 and 18 d, respectively, but attained senescence in 8 and 7 d, respectively, after pollination. The higher content of total soluble sugars, reducing sugars and free amino acids was observed in all the floral organs of pollinated flowers than in unpollinated ones. Pollination also up-regulated the activity of hydrolytic (α-amylase, β-amylase, invertase) and proteolytic enzymes (proteases) in floral organs. Amongst floral organs, the lip and perianth possessed highest contents of metabolites. Application of auxin inhibitor (0.25 µM triiodobenzoic acid) and ethylene inhibitor (0.25 µM AgNO3) to the pollinated flowers partially prevented the process of senescence.
- [Show abstract] [Hide abstract] ABSTRACT: The orchid flowers may stay fresh in unpollinated state from few weeks to months but show rapid senescence upon pollination. Metabolic changes related to this phenomenon are less well understood in orchid flowers. Presently, two orchid species, Aerides multiflora Roxb. and Rhynchostylis retusa (L.) Bl., varying in their floral life span were evaluated for their postpollination-induced responses, involving the oxidative stress. The unpollinated flowers of A. multiflora stayed fresh for 17 days and attained senescence in 5 days after pollination (DAP), while those of R. retusa. remained fresh for 24 days and showed senescence in 7 DAP. After pollination, wilting began in 2 to 3 days in A. multiflora and 3 to 4 days in R. retusa. There was a higher electrolyte leakage accompanied by a concomitant increase in the levels of malondialdehyde (MDA) and hydrogen peroxide (H2O2), indicators of oxidative damage in all the organs after pollination while ascorbic acid decreased significantly. The flowers of A. multiflora showed a greater electrolyte leakage, MDA and H2O2 contents as compared to those of R. retusa. Ascorbic acid content, on the other hand, was lower in A. multiflora than in R. retusa, suggesting a higher oxidative damage to the floral organs in the former species. An application of triiodobenzoic acid ( an auxin inhibitor; 0.25 mM) and silver nitrate (ethylene inhibitor; 0.25 mM) to pollinated flowers partially prevented the oxidative damage and consequently the senescence, suggesting the involvement of these hormones. AgNO3 was more effective in delaying senescence.
- [Show abstract] [Hide abstract] ABSTRACT: Bambusa tulda and Thyrsostachys siamensis resemble each other in having an obovate ovary which is hairy and thickened along the apex, a pseudo-crassinucellate ovule with a wide region of attachment, poorly-developed and ephemeral outer integument, an inner integument which fails to grow beyond the nucellus, ‘Polygonum’ type of embryo sac ontogeny, parallel orientation of embryo sac to the long axis of the ovule, multiple antipodals which retain apical position in the embryo sac even during post-fertilization phase of development, an ephemeral nucellus, relatively small bambusoid embryos, and many-layered and apically thickened pericarp. However, they differ from each other in their gynoecial structure, the extent of the development of the outer integument, organization of megaspore tetrads and development-stage-related behaviour of the inner integument in the fertilized ovules. These taxa also differ from other members of the subfamily Bambusoideae in the structure of the mature ovule, endosperm and pericarp.
- [Show abstract] [Hide abstract] ABSTRACT: BHANWRA, R. K., KAUR, N., KAUR, N. & GARG, A., 1991. Embryological studies in some grasses and their taxonomic significance. The species investigated are Lolium multiftorum Lam (tribe Poeae), Rostraria cristata (Linn.) Tzevlev (tribe Aveneae), Cenchrus setigerus Vahl, Digitaria abludens (Roem. et Schult.) Veld, and D. ciliaris (Retz.) Koel (tribe Paniceae). Apart from the number of microsporocytes in a median longitudinal section of each anther lobe, microsporogenesis and male gametophyte development are similar. However, members of subfamilies Pooideae and Panicoideae show marked differences in structure of the ovary, ovule and post-fertilization development. Lolium multiftorum and R. cristata vary in the structure of the dorsal ovary wall, degree of curvature in the megagemetophyte in relation to the longtitudinal axis of the ovule, and structure of the pericarp. Cenchrus setigerus is an aposporic apomict and differs markedly from species of Digitaria in this respect, in the extent of development of the inner integument and in the constitution of the dorsal ovary wall. The two species of Digitaria show minor embryological differences.
- [Show abstract] [Hide abstract] ABSTRACT: The investigation deals with the reproductive behaviour in Eremopogon foveolatus (Del.) Stapf, a member of the tribe Andropogoneae. The magaspore mother cell or the products of its meiotic division degenerate in a majority of ovules and four–nucleate unreduced embryo sacs are formed from the surrounding cells of the nucellus. Eight–nucleate reduced embryo sacs are also formed in some ovules but the percentage of such ovules is very low. The unreduced egg develops parthenogenetically but fertilization of the polar nucleus appears to be essential for the formation of endosperm.
- [Show abstract] [Hide abstract] ABSTRACT: A perusal of literature showed that a little is known about the metabolic changes related to senescence in orchid flowers. It was observed that unpollinated flowers of Cymbidium pendulum (Roxb.) Sw. remained fresh for 20 days and senesced within 8 days after pollination (DAP), while that of Cymbidium aloifolium (L.) Sw. took 18 days when unpollinated but showed senescence in 7 DAP. A higher level of electrolyte leakage was recorded in all the floral organs of pollinated flowers in both the species. There was a concomitant increase in levels of malondialdehyde (MDA) and hydrogen peroxide (H2O2); indicators of oxidative damage, in all the organs for both the species. Ascorbic acid, on the other hand, decreased significantly. Higher amount of electrolyte leakage, MDA and H2O2 content were recorded in C. pendulum as compared of the other species while the ascorbic acid, on the other hand, was observed to be decreased and this decrease was more in C. pendulum than C. aloifolium suggesting a higher oxidative damage to the floral organs in the former species than the latter. TIBA, i.e. tri-iodobenzoic acid (an auxin inhibitor; 0.25 μM) and silver nitrate (ethylene inhibitor; 0.25 μM) application to pollinated flowers partially prevented the elevation of oxidative damage and consequently senescence suggesting the involvement of these hormones in governing these changes in orchid flowers. Comparatively, AgNO3 was more effective than TIBA in delaying senescence.
- [Show abstract] [Hide abstract] ABSTRACT: If left unpollinated, the flowers ofAerides multiflora (Roxb.) andRhynchostylis retusa (L.) Bl. can remain fresh for 17 and 24 d, respectively. However, they begin to wilt at 2 to 3 days after pollination (DAP) and 3 to 4 DAP, respectively, and become senescent at 5 DAP and 7 DAP, respectively. When measured at two developmental phases — Stage 1, start of wilting and Stage 2, progression to senescence — all the floral organs from pollinated flowers had higher contents of total soluble sugars, reducing sugars, and free amino acids than those from unpollinated flowers. A corresponding increase was noted in the activities of hydrolytic enzymes, i.e., α-amylase, β-amylase, and invertase, and proteolytic enzymes (proteases) in those organs. This indicated that signals related to pollination had up-regulated those activities, leading to a breakdown of complex molecules into simpler ones for mobilization. The amounts of sugars and enzyme activity were relatively greater in the pollinated flowers ofA. multiflora compared withR. retusa, and levels were always higher in the floral lips and perianths. When inhibitors of auxin (0.25 mM TIBA) or ethylene (0.25 mM AgNO2) were applied to the pollinated flowers, their senescence was partially prevented, thus signifying hormonal involvement in governing the pollination-induced biochemical alterations normally found in those organs.
- [Show abstract] [Hide abstract] ABSTRACT: Development of pollinium has been studied in Cymbidium aloifolium (L.) Sw. (tribe Cymbidieae) and Smitinandia micrantha (Lindl.) Holtt. (tribe Vandeae) of the family Orchidaceae. The anther primordium develops two lobes oriented towards the labellum. Each lobe has a group of archesporial cells, which divide mitotically so as to form a spherical mass of sporogenous cells, in which there is differentiation of a dorsiventral plate of elongated sterile cells. In C. aloifolium, the sterile plate extends into about three-fourths of the fertile tissue, whereas in S. micrantha it is complete but asymmetrically oriented. Synchronous meiosis in the microsporocytes is followed by simultaneous cytokinesis so as to form microspore tetrads which organize into pollinia. Centripetal disintegration of the sterile plate during development of the male gametophyte forms two perforate (hollow) pollinia in C. aloifolium, but four unequal pollinia in S. micrantha. The anther wall is composed of an epidermis, an endothecium, two to three middle layers and the tapetum. The tapetum disorganizes during development of the male gametophyte, while the endothecium and adjacent middle layers develop fibrous thickenings.
- [Show abstract] [Hide abstract] ABSTRACT: In Cymbidium pendulum (Roxb.) Sw., an important ornamental orchid, post-pollination induced developmental changes in perianth, megasporogenesis and female gametophyte were examined in relation to time. The pollen grains germinate 24 hr after pollination. The pollen tubes grow through the loose tissue lining the central canal of the column and reach its base 10 days after pollination. The three placental ridges of ovary show meristematic activity at 2 days after pollination. Their ultimate branches form ovule primordia at 26 days after pollination. A hypodermal archesporial cell differentiates at this stage that directly acts as a megaspore mother cell. It undergoes meiosis at 42 days after pollination and the chalazal dyad cell forms an Allium type of embryo sac at 54 days after pollination.
- [Show abstract] [Hide abstract] ABSTRACT: The anther in Rhynchostylis retusa Bl. is bisporangiate, incumbent and with a five layered wall comprising an epidermis, an endothecium, two middle layers and a glandular tapetum of uninucleate cells. The sporogenous tissue after several cycles of mitotic divisions assumes a horse-shoe-shaped configuration around a strip of sterile cells. Progressive disintegration of the sterile cells during maturity indicates their nutritive function. Meiotic cycle in the pollen mother cells leads to the formation of isobilateral, tetrahedral, decussate, and rarely linear or T-shaped microspore tetrads which aggregate into two perforate pollinia. The male gametophyte is shed at the two celled stage.
- [Show abstract] [Hide abstract] ABSTRACT: Bambusa tulda and Thyrsostachys siamensis resemble each other in having an obovate ovary which is hairy and thickened along the apex, a pseudo-crassinucellate ovule with a wide region of attachment, poorly-developed and ephemeral outer integument, an inner integument which fails to grow beyond the nucellus, «Polygonum» type of embryo sac ontogeny, parallel orientation of embryo sac to the long axis of the ovule, multiple antipodals which retain apical position in the embryo sac even during post-fertilization phase of development, an ephemeral nucellus, relatively small «bambusoid» embryos, and many-layered and apically thickened pericarp. However, they differ from each other in their gynoecial structure, the extent of the development of the outer integument, organization of megaspore tetrads and development-stage-related behaviour of the inner integument in the fertilized ovules. These taxa also differ from other members of the subfamily Bambusoideae in the structure of the mature ovule, endosperm and pericarp.
- [Show abstract] [Hide abstract] ABSTRACT: While examining the pollen fertility in different genotypes of soybean (Glycine max (L.) Merr.), precocious pollen germination was noticed in all the ten anthers at bud, half-open flower and fully-open flower stages. Genotypic variation existed for this trait and out of the six genotypes evaluated, 'Palam soya' showed the least germination (17%) while 'Harit soya' had the highest germination (90%) at half-open stage. At fully-opened stage, all the pollen grains appeared to be germinated prior to their release from anthers. Stigma receptivity was relatively more in genotypes having higher precocious pollen germination indicating a positive correlation between the two. Some preliminary observations on this phenomenon, hitherto unknown in soybean, are reported here that may have significant implications in soybean breeding.
Chandigarh, Chandīgarh, India
- Department of Botany