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991.
调查了印度东北部梅加拉亚邦(Meghalaya)3个黄兰种植区(Umdihar,Umsaw和Mawlein)内丛枝菌根真菌和暗隔真菌的侵染。分离和鉴定了丛枝菌根真菌孢子,根据不同黄兰种植区内菌根菌种分布和丰富度评价了菌根菌多样性和寄主选择性。结果表明,丛枝菌根真菌侵染显著高于暗隔真菌。丛枝菌根真菌和暗隔真菌的侵染分别是50.91%~58.95%和1.84%~4.11%。真菌孢子密度在三个种植区内变化较大(p0.05)。在所鉴定的7个属29个菌种中,球囊霉属菌种的丰富度最高。Sorenson系数在0.35-7.0之间。种植区内菌种丰富度在2.0~2.9之间。总的菌种丰富度与总的相对丰富度显著相关(p=0.001)。真菌分布、相对丰富度和主成分分析结果表明,大果球囊霉(Glomus macrocarpum)、Glomus multicaulic、缩不囊霉(G.constrictum)和无梗囊霉是黄兰最偏好的菌种,可能是由于寄主的营养获得和生长较为适当。图6表5参27。 相似文献
992.
Phosphorus (P) in soil exists both in organic and inorganic forms and their relative abundance could determine P supplying capacity of soil. Differential input of exogenous and plant-mediated phosphorus and carbon in soil under different land-uses could influence P availability and fertilizer P management. While the effect of land-use on soil organic carbon (SOC) is fairly well-documented, its effect on soil P fractions is relatively less known. We investigated the effect of different land-uses including rice–wheat, maize–wheat, cotton–wheat cropping systems and poplar-based agroforestry systems on soil P fractions and organic carbon accrual in soils. Total P concentration was the highest under agroforestry (569 mg P kg?1) and the lowest under maize–wheat (449 mg P kg?1) cropping systems. On the contrary, soils under rice–wheat had significantly higher available P concentration than the agroforestry systems, probably because of higher fertilizer P application in rice–wheat and prevailing wetland conditions during rice growth. In soils under sole cropping systems viz. rice–wheat, maize–wheat and cotton–wheat, inorganic P was the dominant fraction and accounted for 92.2–94.6% of total P. However, the soils under agroforestry had smaller proportion (73%) of total P existing as inorganic P. Among soil P fractions, water soluble inorganic P (0.13–0.26%) represented the smallest proportion inorganic P in soils under different land-uses. Agroforestry showed significantly (p < 0.05) higher concentrations of SOC than the other land-uses. Soil organic C was significantly correlated with soil P fractions. It was concluded that poplar-based agroforestry systems besides leading to C accrual in soil result in build-up of organic P and the P supplying capacity of soil. 相似文献
993.
994.
Fodder grass productivity and soil fertility changes under four grass+tree associations in Kerala, India 总被引:1,自引:0,他引:1
Adapted tree+grass combinations make a valuable contribution to forage production in the Indian peninsula, but knowledge of
the interactive effects between trees and grasses on their production is limited. We, therefore, conducted a field experiment
involving combinations of four trees and grasses, besides monospecific grass controls, for seven years, to investigate grass
productivity in association with leguminous and non-leguminous multipurpose trees (MPT) having disparate canopy architecture,
and to assess the end-of-rotation soil fertility changes. Post rotation changes in herbage productivity were evaluated by
growing teosinte (Zea mexicana) for three years. The four MPTs were Acacia auriculiformis, Ailanthus triphysa, Casuarina equisetifolia and Leucaena leucocephala. Grasses included Pennisetum purpureum (hybrid napier), Brachiaria ruziziensis (congo signal), Panicum maximum (guinea grass) and teosinte. Lower tree branches were pruned from fifth year. Understorey herbage production increased until
three years in all tree+grass combinations, but declined subsequently, as tree crowns expanded. Overall, casuarina among MPTs,
and hybrid napier and guinea grass among forage crops, were more productive than others. Pruning MPTs generally favoured greater
herbage production. Understorey light levels for acacia, ailanthus, casuarina and leucaena were 17, 60, 55 and 55% of that
in the open at five years. During the post-rotation phase, MPT plots were characterised by higher soil nutrient capital and
consequently teosinte yields were higher than in the treeless control treatment. All previous tree-grass combinations showed
an increasing trend till two years after MPT felling. Yield levels declined subsequently, despite at variable rates. Careful
selection of the tree and grass components is, therefore, crucial for optimising herbage productivity in silvopastoral systems.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
995.
Pravat Manjari Mishra A. Sree Bandita Dash Mallika Panigrahi Susanta Kumar Padhan 《Fitoterapia》2010,81(8):977-981
A deoxy lupane triterpene carboxylic acid, lup-20(29)-en-24-oic acid (1), was isolated from the active chloroform extract of Finlaysonia obovata, a latex exuding mangrove plant. Its structure was evaluated on the basis of different spectroscopic methods, including extensive 1D and 2D NMR spectroscopy. Lup-20(29)-en-24-oic acid (1) has shown moderate antimicrobial activity, against some fish pathogens. 相似文献
996.
Initial spacing and pruning are silvicultural strategies that influence the resource acquisition capabilities of trees. A
field study was conducted in the humid tropics of peninsular India to test the assumptions that: (1) high stand density of
Acacia
mangium induces greater root uptake capacity close to the stem and from the subsoil; and (2) crown pruning stimulates greater root
uptake capacity at proximal points. Root activity pattern of two-year-old A. mangium was evaluated as a function of three population densities (1,250, 2,500 and 5,000 stems ha−1), with, and without 50% crown pruning, using 32P soil injection. The label was placed at 25, 50 and 75 cm lateral distances and at 30 and 60 cm depth. Low density stands
(1,250 stems ha−1) generally showed higher 32P recovery (P < 0.01), which was exaggerated by pruning. Pruned low density stands had 34% root activity at 25 cm, as against 23% for unpruned.
The low density stands also showed higher root activity at 75 cm, signifying greater root spread. We suggest that high stem
densities favour restricted spread of absorbing roots and may facilitate competitive downward displacement of roots. Pruning
the lateral shoots at low stem densities may simulate this to some extent. The net outcome of interactions, however, will
depend on trade-offs between stem density and tree management over time. 相似文献
997.
Vanessa Prigge Raman Babu Biswanath Das M. Hernández Rodriguez Gary N. Atlin Albrecht E. Melchinger 《Euphytica》2012,185(3):453-463
Single crosses (SC) of elite inbreds and open-pollinated populations (OP) are suitable source germplasm for doubled haploid
(DH) line development in hybrid maize breeding, given that they combine a high population mean ([`(x)] \overline{x} ) for testcross performance with adequate response to selection (
\Updelta G \Updelta G ). This is the first study reporting testcross grain yield (TCGY) and dry matter content (TCDMC) evaluations of 131 DH lines
developed from ten tropical source germplasm comprising five OP (OP1–OP5) and five SC (SC1–SC5). Gene diversity (d) and the average number of alleles (a
r
) per locus was estimated for DH lines based on 24 simple sequence repeat markers. Analysis across three environments revealed
no significant differences between [`(x)] \overline{x} of OP- and SC-derived DH lines for TCGY and TCDMC. Significant genetic variance for both traits was only detected among OP-derived
DH lines which may be explained by a larger number of segregating quantitative trait loci (QTL) as suggested by higher d and a
r
values than in SC-derived DH lines. The usefulness criterion (
U = [`(x)] + \Updelta G U = \overline{x} + \Updelta G ) was higher for OP-derived DH lines for TCDMC, but higher for SC-derived DH lines for TCGY. DH lines from OP1, OP2, and OP3
showed high TCGY, suggesting that they may be useful in tropical hybrid breeding. We conclude that tropical OP represent a
valuable source of untapped genetic variation that can efficiently be exploited with DH technology for hybrid maize breeding. 相似文献
998.
Iaibadaiahun Nongrum Shrawan Kumar Suman Kumaria Pramod Tandon 《Journal of Crop Science and Biotechnology》2012,15(2):101-105
Random Amplified Polymorphic DNA (RAPD) markers were utilized for determination of diversity within and among the three populations
of Nepenthes khasiana Hook f., a threatened insectivorous plant of Meghalaya (India). A total of 90 bands were generated from 10 random amplification
polymorphic DNA (RAPD) primers of which 71 were found to be polymorphic (78.89%). Nei’s gene diversity (h) ranged between 0.124–0.201 with overall diversity of 0.228 while Shannon’s information index I) values recorded between 0.187–0.308 with an average value of 0.352. The values of gene flow (Nm = 1.284) and the diversity among populations (0.280) recorded demonstrates higher genetic variation within the population.
AMOVA analysis revealed a low level of genetic variation (21.96%) among the populations. This study indicates that some variation
still exists within and between the existing populations of N. khasiana, thus, these populations could provide materials for re-establishing of this important rare and threatened species. 相似文献
999.
Amarchand Chordia Murugan Jibu Thomas Raj Kumar Rajagopal AbulKalamAzad Mandal 《Journal of Crop Science and Biotechnology》2012,15(1):53-57
Effects of exogenous application of ascorbic acid on physiological and metabolic changes in tea were investigated in the present
study. The highest improvement in yield was evident in response to regular application (a day after every harvest) of ascorbic
acid at 600 ppm followed by 400 ppm. Foliar application of ascorbic acid (600 ppm) at regular intervals enhanced chlorophyll
a and b contents besides a significant increase in total polyphenols and catechins when compared to the untreated control. Exogenous
application of ascorbic acid at alternate harvesting rounds increased the activity of polyphenol oxidase whereas ascorbate
peroxidase remained unchanged. An increase in phenylalanine ammonia lyase activity was noticed with foliar application of
ascorbic acid irrespective of its concentrations. Theaflavins and thearubigins of made tea showed an increase when ascorbic
acid was applied with 400 and 600 ppm at alternate intervals. The scores of brewed tea liquor characteristics, viz. infusion,
color, strength, and briskness were higher even at the lower concentration of ascorbic acid treatment. Results suggest that
foliar application of ascorbic acid (400 ppm) proved to be a useful measure to improve the yield, physiological attributes,
and antioxidant properties of tea. 相似文献
1000.
Commercial viability of three cytoplasmic-nuclear male sterility (CMS) systems (A4, A5 and Av) as potential alternatives to the most widely used A1 system in pearl millet (Pennisetum glaucum (L.) R.Br.) was evaluated in terms of stability of complete male sterility of four isonuclear A-lines (81A1, 81A4, 81A5 and 81Av) and the level and stability of male fertility restoration of their 44 single-cross hybrids. Lines 81A4 and 81A5 had no pollen shedders (PS), and there were very low frequency of non-PS plants of these A-lines that had a maximum of 1–5%
selfed seedset (SSS). In 81A1 and 81Av,there were, albeit low frequency (<1%) of PS plants, and relatively higher frequency of the non-PS plants in these two lines,
the more so in 81Av,had 1–5% and even greater SSS. Some hybrids made on each of the three A-lines (81A1, 81A4 and 81Av) had high and stable male fertility, while others made on the same three A-lines displayed large variation in SSS across
the environments, the more so in case of hybrids made on 81Av. These results indicate that the A4 CMS system provides a better alternative to the A1 CMS system, while the Av system does not. On the basis of highly stable male sterility and the highest frequency of pollinators behaving as maintainers,
the A5 CMS system appeared to be the best for A-line breeding. The commercial viability of this CMS system in breeding R-lines of
grain hybrids, however, still remains to be ascertained as no hybrid on it was fully male fertile in any environment.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献