Allelopathic interference of Populus deltoides with some winter season crops

The performance of some winter season crops, namely Triticum aestivum, Lens culinaris, Phaseolus mungo, Avena sativa, Trifolium alexandrinum, Brassica juncea and Helianthus annuus was studied in association with Populus deltoides under alley cropping practice in two sets of fields in Punjab, North India. In one, the parent soil was retained (Sp), while in the other, the parent soil was replaced with soil collected from an area devoid of P. deltoides trees (Sr). Germination, plant height and biomass of the crops at 30 and 60 days after sowing (DAS) were reduced by 10 to 30% in both the P. deltoides fields compared to the ones without trees (Sc). The observed reduction was more pronounced in Sp fields than in Sr fields. Maximum reduction was observed in the case of B. juncea and least in T. alexandrinum. Germination and seedling growth of all the test crops except A. sativa and T. aestivum was found to be significantly reduced in response to the aqueous leachates of P. deltoides leaves. Likewise, the seedling length and dry weight of L. culinaris and T. aestivum were significantly reduced in litter amended soil. Litter and soil from P. deltoides fields were found to be rich in phytotoxic phenolics, the amount of which was more in Sp fields compared to Sr and control fields (Sc). Based on the study, the observed reductions could be attributed to the allelopathic interference of the tree with the crops through the release of phytotoxic phenolics from leaves and litter, which are continuously added to the soil

Alternative control of littleseed canary grass using eucalypt oil

Globally, huge amounts of synthetic herbicides are used to manage weeds in arable lands. However, their widespread use has resulted in various toxicological effects on the environment and human health, besides resulting in the emergence of herbicide-resistant weed biotypes. To overcome these problems, there is an urgent need to search for novel compounds, particularly natural plant products, with potential herbicidal activity. In this area, we studied the phytotoxic effect of volatile oil from lemon-scented eucalypt on littleseed canary grass, a noxious weed of wheat fields. Our findings show that under laboratory conditions the emergence and earlier growth of the weed decreased and completely ceased using a very low concentration of eucalypt oil (0.0714%, v/v). Treatment with eucalypt oil of the 4-week-old pot-raised weeds caused visible damage such as chlorosis and necrosis, wilting and even plant death. The effect was concentration-dependent. At low concentrations, 2.5 and 5%, v/v of eucalypt oil, plants were damaged but recovered later, whereas at concentrations higher than 5%, v/v, of eucalypt oil plants showed severe injury with little or no sign of recovery, and death. There was a severe effect on the photosynthetic and respiratory ability of treated plants 7 and 21 days after treatment. Eucalypt oil treatment caused a rapid electrolyte leakage in the P. minor leaf tissues, indicating a loss of membrane integrity. The study concludes that lemon-scented eucalypt oil offers a good option for control of littleseed canary grass and could be included as a viable component of integrated weed management under sustainable agricultural practices

Allelopathic interference of Populus deltoides with some winter season crops

Abstract -The performance of some winter season crops, namely Triticum aestivum, Lens culinaris, Phaseolus mungo, Avena sativa, Trifolium alexandrinum, Brassica juncea and Helianthus annuus was studied in association with Populus deltoides under alley cropping practice in two sets of fields in Punjab, North India. In one, the parent soil was retained (S p ), while in the other, the parent soil was replaced with soil collected from an area devoid of P. deltoides trees (S r ). Germination, plant height and biomass of the crops at 30 and 60 days after sowing (DAS) were reduced by 10 to 30% in both the P. deltoides fields compared to the ones without trees (S c ). The observed reduction was more pronounced in S p fields than in S r fields. Maximum reduction was observed in the case of B. juncea and least in T. alexandrinum. Germination and seedling growth of all the test crops except A. sativa and T. aestivum was found to be significantly reduced in response to the aqueous leachates of P. deltoides leaves. Likewise, the seedling length and dry weight of L. culinaris and T. aestivum were significantly reduced in litter amended soil. Litter and soil from P. deltoides fields were found to be rich in phytotoxic phenolics, the amount of which was more in S p fields compared to S r and control fields (S c ). Based on the study, the observed reductions could be attributed to the allelopathic interference of the tree with the crops through the release of phytotoxic phenolics from leaves and litter, which are continuously added to the soil. Dans l'un des groupes le sol d'origine a été conservé (S p ), tandis que dans l'autre il a été remplacé par un sol prélevé dans un endroit dépourvu de peupliers (S r ). La germination, la taille des plantes et la biomasse des cultures 30 et 60 jours après le semis ont été réduites de 10 à 30 % dans les deux groupes de champs comparativement aux champs sans peupliers (S c ). La réduction observée était plus forte dans les champs S p que dans les S r . La réduction maximum a eu lieu pour les cultures de B. juncea et, à un moindre degré, pour T. alexandrinum. Des filtrats aqueux de feuilles de P. deltoides ont réduit significativement la germination et la croissance des pousses de toutes les cultures testées, à l'exception de A. sativa et T. aestivum. De même, la longueur des pousses et le poids sec des cultures de L. culinaris et T. aestivum ont été significativement réduits dans le sol amendé par de la litière. Nous avons trouvé que la litière et le sol des champs de P. deltoides sont riches en substances phénoliques phytotoxiques ; les quantités sont plus importantes dans les champs S p que dans les S r et les témoins (S c ). Selon cette étude les réductions observées peuvent être attribuées à l'interfé-rence allélopathique du peuplier avec les cultures par l'intermédiaire de substances phénoliques phytotoxiques provenant des feuilles et de la litière, qui s'incorporent continuellement au sol

Exhibition of allelopathy by Parthenium hysterophorus L. in Agroecosystems

The yield and biomass of five pulse crops namely, Cyamopsis tetragonoloba, Phaseolus aureus, Phaseolus mungo vars. MI-1 Pantu-19 and Vigna umbellata when grown in soil earlier infested with Parthenium hysterophorus were greatly reduced. The seed germination parameters and relative growth rate of the crops were also reduced. The soil inhabited with P. hysterophorus was not rendered poor in its available macronutrients especially nitrogen, phosphorus and potassium. On the contrary, it was enriched. However, the texture, pH and conductivity of the P. hysterophorus inhabited soil were almost the same as that of the control (about 100 m away). On the other hand, the amount of soil chemicals was found to be maximum in P. hysterophorus inhabited soil sampled from all the three depths (0-7, 14-21 and 28-35 cm depths), compared to respective soil layers from the control. The bio-efficacy studies of the soil chemicals conducted on a representative plant Phaseolus aureus, points to its inhibitory nature. Not only the different germination parameters were affected but the mature plants too showed reduced cell survival, contents of water and chlorophyll compared to the control. Thus, the chemicals accumulated in the soil infested with P. hysterophorus, qualify to be called as allelochemicals

Status of floor vegetation under some monoculture and mixculture plantations in North India

A study conducted to assess the floor vegetation shows the presence of 17 species under Populus deltoides in comparison to 28, 29 and 35 under Albizia lebbeck, Dalbergia sissoo and mix-culture plantations, respectively. Further, the biomass and density of floor vegetation is considerably reduced under P. deltoides compared to other plantations. In addition, the indices for species richness, evenness, dominance and diversity are also reduced under P. deltoides showing some inhibitory mechanism being operative under these plantations. Based on available literature, allelopathy is speculated to be responsible for this reduction

Allelopathy of gymnospermous trees

The present paper reviews the available literature on the allelopathy of gymnosperms which constitute the famous boreal forests known for their high quality timber and other products of great commercial importance. Nineteen genera belonging to six of the seven taxonomic families of conifers comprising one of the most dominating and largest group of present day gymnosperms, are reported to show the phenomena of allelopathy. The available information signifies the role these mighty trees play in determining the understorey vegetation, ecological succession and forests dynamics besides causing regeneration problems to the donor trees. The allelochemicals, identified from these plants, responsible for such interactions have also been summarised. In most of the cases the leaching of phenolics from the litter predominantly of tree needles, which remain on the ground for a longer time due to slow decomposition rate, are held responsible for these interactions

Phytotoxic effects of Parthenium hysterophorus residues on three Brassica species

A study was conducted to assess the phytotoxicity of residues of Parthenium hysterophorus, an exotic invasive weed, towards the growth of three Brassica species (Brassica campestris, Brassica oleracea and Brassica rapa). The early growth of crops, measured in terms of seedling length and dry weight, was significantly reduced when grown in soil amended with varying amounts of Parthenium residues. A direct relationship was observed between the amount of residue incorporated in the soil and growth reduction. This adverse effect on Brassica crops indicates the presence of some growth-retardatory substances which are possibly released by the residues into the soil medium. In order to test this, aqueous extracts (1, 2, and 4%) of residues were prepared. It was observed that, in a laboratory bioassay, these extracts severely reduced the early growth of Brassica species, thereby indicating the presence of some water-soluble, inhibitory principles in Parthenium residues. A significant amount of the phenolics, the largest group of secondary metabolites usually implicated in allelopathy, was estimated in residue extracts, as well as in residue-incorporated soil. The phenolic content increased with increasing residue concentration, thereby showing their direct involvement in the observed growth inhibitions. Therefore, the study establishes that Parthenium residues exert an allelopathic influence on the early growth of Brassica crops by releasing water-soluble phenolics into the soil

Cell phone radiations affect early growth of Vigna radiata (mung bean) through biochemical alterations

The indiscriminate use of wireless technologies, particularly of cell phones, has increased the health risks among living organisms including plants. We investigated the impact of cell phone electromagentic field (EMF) radiations (power density, 8.55 µW cm-2) on germination, early growth, proteins and carbohydrate contents, and activities of some enzymes in Vigna radiata. Cell phone EMF radiations significantly reduced the seedling length and dry weight of V radiata after exposure for 0.5, 1, 2, and 4 h. Furthermore, the contents of proteins and carbohydrates were reduced in EMF-exposed plants. However, the activities of proteases, α-amylases, β-amylases, polyphenol oxidases, and peroxidases were enhanced in EMF-exposed radicles indicating their role in providing protection against EMF-induced stress. The study concludes that cell phone EMFs impair early growth of V radiata seedlings by inducing biochemical changes