Radicle Growth Research Articles

Seed dormancy and germination of Asarum sieboldii, a disjunct relict species in East Asia.

Disjunct species in the same genus are a common feature of the flora in the temperate forests of East Asia and eastern North America. This study aimed to evaluate whether the kind of seed dormancy was maintained after species in the genus Asarum (Aristolochiaceae) were separated from their common ancestor. We classified the seed dormancy of Asarum sieboldii, an East Asian species, based on a phenology study and experiments in controlled temperature conditions, and then compared it to that of the previously studied A. canadense, an eastern North American species. The underdeveloped embryo of A. sieboldii grew and germinated (radicle emergence) in autumn but shoot emergence did not occur until the following spring. The seeds of A. sieboldii had deep simple epicotyl morphophysiological dormancy because the seeds with emerged radicle required a relatively long period of cold stratification to break epicotyl dormancy and produce a shoot. Although the seed of A. sieboldii had weaker radicle dormancy and stronger epicotyl dormancy compared to A. canadense, the kind of seed dormancy was the same for the two species. The trait of seed dormancy was inherited from a shared common ancestor and maintained in populations well after the two species (or their ancestors) separated. However, quantitative differences in temperature requirements for radicle and shoot emergence suggest the possibility of adaptation to the environment.

Machine learning in agriculture: from silos to marketplaces.

The increasing global population combined with climate change present a major challenge for agriculture. Most crops have been bred to perform in specific environments, and with the time required to produce new varieties, it is unlikely that breeders will be able to adapt varieties to the changing climate (Abberton et al., 2016). There is an urgent need to develop new approaches to accelerate the production of high performing resilient crop varieties. Crop breeding has seen many changes in recent decades, from the application of molecular markers, through to genetically modified, and more recently, genome edited crops (Scheben et al., 2017). However, these approaches are often limited by our lack of understanding of the genomic basis for complex traits, even with the deluge of data being generated by new genome sequencing and phenomics technologies. New approaches are required to translate this explosion of data into improved crop varieties.

Radicle emergence test predicts normal germination percentages of onion seed lots with different cultivars and genotypes

Aims: To test radicle emergence count in order to predict normal germination percentages of onion lots.Methods and Results: This work was conducted to test the potential for 2 mm radicle emergence (RE) to predict normal seed germination percentages of 20 onion seed lots. In the first stages of the study RE counts at 72, 76 and 80 h were highly predictive (p<0.001, R2=0.94-0.95) of normal germination after 12 days. In the second stage, the regression formula (y=45.9+0.52x) developed for the 80th hour radicle emergence to predict normal germination of 20 seed lots at various aging levels collected from the market. RE counts (%) of the 20 lots at 80 h were used to predicted values by using the formula. Actual normal percentages of 20 lots were determined after 12 days of germination testing. Then regression analysis was performed on both values. Results showed that predicted and actual normal germination percentages were highly related to actual normal germination percentages (R2=0.95, p<0.001). Means of the predicted (79.6%) and actual (80.4%) values were very similar. Results indicated that RE testing has a potential to estimate normal germination percentages of onion seed lots. Conclusions: RE count at 80h was highly related to normal germination percentages after 12 days (p<0.001, R2=0.95) in commercial onion seed lots.Significance and Impact of the Study: RE testing can be used in the prediction of normal germination percentages of any commercial onion seed lots within a short period, rather than waiting until the final count (12 days) in onion germination tests.

Phytotoxic condensed organic compounds are common in fast but not slow pyrolysis biochars

Biochar chemistry varies with feedstock and pyrolysis parameters: fast pyrolysis may not provide sufficient time for volatile compounds – some phytotoxic – to escape from biochar particles. Lettuce and radish seeds were treated with biochar leachate derived from 100 slow pyrolysis biochars (20 wood species, each pyrolyzed at 300–700 °C for 60 min), and 20 fast pyrolysis biochars (two species pyrolyzed at 500 and 550 °C for 1–5 min). Slow pyrolysis biochar leachates enhanced radicle extension growth by (60% for lettuce; 16% for radish), while fast pyrolysis biochar leachates inhibited radicle growth by (63% for lettuce; 8% for radish). Slow pyrolysis biochars showed higher concentrations of Ca, Mg, K, Fe, Mn, and Zn than fast pyrolysis biochars, whereas fast pyrolysis biochars generally showed higher concentrations of phytotoxic volatile fatty acids, such as acetic and pentanoic acid. These results suggest the importance of extended pyrolysis residence times in producing high-nutrient biochars free from toxicity effects.

Secondary Metabolites with Agricultural Antagonistic Potentials from Beauveria felina, a Marine-Derived Entomopathogenic Fungus.

Soil-borne pathogens and weeds could synergistically affect vegetable growth and result in serious losses. The investigation of antagonistic metabolites from a marine-derived entomopathogenic fungus, Beauveria felina, obtained polyhydroxy steroid (1), tricyclic diterpenoid (2), isaridin (3), and destruxin cyclodepsipeptides (4-6). The structures and absolute configurations of new 1-3 were elucidated by extensive spectroscopic and X-ray crystallographic analyses, as well as electronic circular dichroism (ECD) calculations. Compounds 1 and 2 showed antifungal activities against carbendazim-resistant strains of Botrytis cinerea, with the minimum inhibitory concentration (MIC) values ranging from 16 to 32 μg/mL, which were significantly better than those of carbendazim (MIC = 256 μg/mL). Compound 5 exhibited significant antagonistic activity against the radicle growth of Amaranthus retroflexus seedlings, which was almost identical to that of the positive control (2,4-dichlorophenoxyacetic acid). The structure-activity differences of 4-6 suggested that the Cl atom in HMPA1 and β-Me in Pro2 should be the key factors to their herbicidal activities. Besides, compounds 3-6 showed moderate nematicidal activities against Meloidogyne incognita. These antagonistic effects of 1-6 were first reported and further revealed the synergistically antagonistic potential of B. felina to be developed into the biopesticide.

Seed dormancy of 80 tropical montane forest species in Sri Lanka, the first dormancy profile for a tropical montane forest community.

Community-level seed dormancy studies are important in understanding the dynamics of plant communities and adaptations of species to their habitat. Our aim was to develop a seed dormancy profile for tropical montane forests of Sri Lanka, which are a global biodiversity hotspot, and compare it to the profile made using a world database for this vegetation type. Germination, imbibition and embryo length : seed length ratio of seeds were determined for 80 Sri Lankan montane forest species. Seeds of 31 species were fast-germinating with a median length of germination (MLG) <30days and the remaining 49 were slow-germinating with MLG >30days. Embryos of six fast-germinating species grew prior to radicle emergence, indicating morphological dormancy (MD). The other 25 fast-germinating species had non-dormant (ND) seeds. Manually scarified seeds of two species imbibed significantly more water than non-scarified seeds, revealing physical dormancy (PY). Embryos of 20 slow-germinating species grew prior to radicle emergence, confirming morpho-physiological dormancy (MPD). The remaining slow-germinating species had a fully developed embryo and thus physiological dormancy (PD). The percentage of species with ND seeds and with MD, MDP, PD and PY was 31, 7.5, 25, 34 and 2.5, respectively. Species with dormant seeds (70%) dominate the Sri Lankan montane forest community similar to the world database, with 85% dormant seeds. Seed dormancy may be an adaptation that prevents seeds from germinating during the Sri Lankan dry season from December to March when conditions are unfavourable for seedling growth due to low water availability.

Evaluation of physiological quality of Corn seeds by GroundEye L800® system

The usual vigor test of companies for batches of genetic corn seeds is carried out based on the potential of seeds to germinate at low temperatures, not being suitable for the warm regions of the country, since there is a low correlation between laboratory and field results for these cases. An alternative to this method is the GroundEye L800® system, which evaluates vigor by the performance potential of corn seedlings. Thus, the objective was to evaluate the efficiency of the GroundEye L800® equipment in determining the vigor of seeds of the genetic category of corn. Seeds from 36 corn batches were used in this study. The parameters evaluated were germination, radicle emergence test (RET), emergence on flower-bed, besides the image analysis using GroundEye L800® system. RET, the method generally used by companies, showed a significant difference in emergence results compared to those found on flower-bed, with no positive correlation. The GroundEye L800 process and the flower-bed emergence test did not differ statistically. GroundEye L800® equipment is promising for assessing the physiological potential of corn seeds.

Radio frequency plasma capacitor can increase rates of seeds imbibition, germination, and radicle growth

Radio frequency capacitors can be used to accelerate seed imbibition, germination, increase the growth of plants seedlings, poration and corrugation of the bio-tissue surfaces without the side effects of RONS generated by cold plasma jets. Atomic force microscope data show that the plasma lamp produced morphological changes in the seed coat. Magnetic resonance imaging studies showed the acceleration of water uptake in seeds treated with radio frequency capacitors of plasma lamps. Plasma capacitor can accelerate radicle growing rates.

Seed germination in Narcissus yepesii (Amaryllidaceae): clinal variation in the morphophysiological dormancy levels.

Seed dormancy classes determine both population and species-level processes which can be crucial in the life cycle of many plants. However, there are no studies of a dormancy cline between levels of morphophysiological dormancy (MPD). We aimed to determine the class of seed dormancy of Narcissus yepesii exhibits in order to explore links between different dormancy levels, previously characterized in two closely related phylogenetic congeners, N. alcaracensis and N. longispathus. Experiments were carried out under both near-natural temperature and controlled laboratory conditions. The parameters calculated were mean embryo length, radicle and shoot emergence percentages. The effects of different periods of storage; and different periods with or without GA3 of warm, cold or warm plus cold were analysed. The Narcissus populations from the Baetic System of mountain ranges in south-eastern Spain show clinal variation in a northeast–southwest gradient from intermediate to non-deep complex MPD, through the coexistence of intermediate and non-deep complex MPD in N. yepesii (21 % and 74 %, respectively). In addition, 54 % of stored seeds were able to show both levels of MPD. Narcissus yepesii occupies an intermediate position between N. alcaracensis and N. longispathus in the geographical distribution and in the clinal germination ranges. It strongly suggests an evolutionary gradient, which connects the intermediate complex MPD with the non-deep complex MPD in southern Iberian daffodils. This is the first study showing a gradient in the evolution between levels of MPD. Our results demonstrate a cline in these levels in response to both an environmental gradient and genetic differences.

Different levels of morphophysiological seed dormancy in Ribes alpinum and R. uva-crispa (Grossulariaceae) facilitate adaptation to differentiated habitats

Aim of the study: To study the germination ecology of two species of the genus Ribes to reveal their levels of morphophysiological dormancy (MPD) and to facilitate the production of plants from seeds, a key tool for population reinforcement.Area of study: Experiments were carried out both outdoors and in the laboratory in Albacete (Spain) with seeds from the Meridional Iberian System mountain range.Material and methods: Seeds from one population of Ribes alpinum and from other of Ribes uva-crispa were collected during several years. Embryo length, radicle and seedling emergence, and effects on germination of stratification and GA3 were analysed to determine the level of MPD.Main results: In R. alpinum, embryo length in fresh seeds was 0.49 mm, needing to grow to 1.30 mm to germinate. Warm stratification (25/10ºC) promoted embryo length enlargement to 0.97 mm. Afterwards, seeds germinated within a wide temperature range. Embryo growth and seedling emergence occur late summer-early autumn. In R. uva-crispa, embryo length in fresh seeds was 0.52 mm, being 2.10 mm the minimal size to germinate. Embryos exposed to a moderately warm stratification (20/7ºC + 15/4ºC) followed by cold (5ºC) grew to 2.30 mm. Then, seeds germinated ≥ 80% when incubated at temperatures ≥ 15/4ºC. Embryos grew in autumn/early winter, and seedlings emerged late winter-early spring.Research highlights: These results showed that R. alpinum seeds have a nondeep simple MPD while R. uva-crispa seeds have a nondeep complex MPD. Moreover, the different germinative models found for each species help explain their installation in distinct habitats.Keywords: Ribes; seed dormancy break; radicle emergence; seedling emergence; nondeep simple and nondeep complex MPD.Abbreviations used: Morphophysiological dormancy (MPD), morphological dormancy (MD), Gibberellic acid (GA3), months (m).

The Effects of Salt Stress in Zinnia (Zinnia sp.) Cultivars During Seed Germination and at the Early Stages of Seedling Growth

The Zinnia genus which belongs to the Asteraceae family is an annual, multipurpose ornamental plant. Zinnia plants are cultivated not only in landscape but also as the potted plant and cut flower. One of the most important problems in the world is salinity in soil and water. The aim of this study was to determine the effects of salinity on twenty Zinnia cultivars during seed germination and early seedling growth. The salt was applied by irrigating seeds with 0 and 100 mM salt solutions. Radicle emergence, seed germination, root, hypocotyl and cotyledon lengths, relative growth index of the root, and seedling fresh weight were evaluated. At the end of the study, the radicle emergence reduction was the highest value in Zinnita Rose (52%). The highest reduction rates on seed germination were at Swizzle Cherry-Ivory, Double Zahara Raspberry Ripple (48%), and Double Zahara Yellow (48%). Root lengths of all Zinnia cultivars were dramatically decreased by salt stress. According to weighted ranked evaluation, Dreamland Ivory and Dreamland Coral were more tolerant to salt stress than other Zinnia cultivars. However, in general Zinnia cultivars were relatively sensitive to salt stress at the germination stage.

Impact of aluminum and zinc oxides on morphological characters, germination, metals accumulation and DNA in fenugreek (Trigonella foenum-graecum)

Abstract Metal nanoparticles (NPs) have several prospective technical implementations; it hassled the issue of unidentified environmental impacts from their release. Zinc and aluminum oxides have been used in numerous sectors including industrial and agriculture products. The present study deals with the impact of various levels (0, 125, 250, 500, and 1000 mg kg−1) of zinc and aluminum oxides NPs on seed germination and seedling growth for both varieties (Qassimi and Yemeni) of fenugreek. The untreated plants were used as a control. Results showed that a severe decline in germination percentage occurred at higher concentrations of ZnO and Al2O3 NPs (1000 mg L−1). Radicle and plumule growth rates for both verities treated with ZnO and Al2O3 NPs inhibited significantly (p > 0.05) by increasing the concentrations of NPs. Moreover, dry and fresh weights of root and shoot of both varieties progressively reduced with increasing NPs concentration. The average accumulation of Zn content ranged from 61 to 334 and 63 to 358 mg kg−1 for root and shoot of Qassimi and Yemeni variety, respectively. The average accumulation of Al varied from 47 to 319 and 46 to 334 mg kg−1 for root and shoot of Qassimi and Yemeni variety, respectively. The translocation factor (TF) ranged from 0.98 to 1.26 for Zn, and from 0.91 to 1.32 for Al. Also, genetic diversity was assessed in fenugreek (Qassimi and Yemeni) by using Strat Codon Targeted (SCoT) markers. High levels of polymorphism have been detected, suggesting that these markers are valuable tools for detecting genetic variation. The finding confirmed that the genetic variation was greater in plants exposed to high levels of nano ZnO and Al2O3 compared to control. In conclusion, the tested metal nano oxides possess an inhibitory effect on plant growth, metal uptake, and genetic variation by both varieties of fenugreek. Such findings significantly improve our knowledge of environmental safety after release to metal oxide nanoparticles.

Single radicle emergence count for predicting vigour of marigold (Tagetes spp.) seed lots

This study was carried out to determine whether a single radicle emergence count (RE) during germination can be used for vigour assessment to estimate field emergence of marigold (Tagetes spp.) seed lots. Six marigold seed lots (Tagetes erecta and T. patula) with normal germination above 75% were germinated using the standard ISTA germination test and radicle emergence (production of 2 mm radicle) counted at regular intervals from 25 to 169 hours. The seed lots were also sown in the field with final seedling emergence assessed after 25 days. Seedling emergence was highly correlated with the radicle emergence count after 49 and 66 hours germination (r = 0.90 and r = 0.91, respectively; P &lt; 0.01) but not with germination percentage (r = 0.26). Thus, the radicle emergence counts at 49 and 66 hours accounted for 81 or 83% of the variation in field emergence, respectively. The results indicate that a 49- or 66-hour count of RE during germination could be used as a vigour test to estimate field emergence for marigold seed lots.

Quantitative proteomics reveals dual effects of calcium on radicle protrusion in soybean

To reveal calcium-mediated germination in soybean, a gel-free/label-free proteomics was performed in radicle of seed imbibed with CaCl2. Morphological analysis presented promoting and suppressing performance of seed growth under 5 and 50 mM CaCl2, respectively. A total of 106 and 581 proteins were identified in response to 5 and 50 mM CaCl2, respectively. Among 33 proteins, which were simultaneously affected by 5 and 50 mM CaCl2 imbibition, proteins related to protein metabolism, cell, development, and stress showed reversed abundance in response to CaCl2 on dose-dependent manner. Notably, protein abundance of late embryogenesis abundant (LEA) 4–5, LEA4, and dehydrin decreased and increased by 5 and 50 mM CaCl2, respectively, consistent with the transcript level. Moreover, inhibited biosynthesis of gibberellic acid repressed growth of 5 mM CaCl2-imbibed soybean, while inhibition of abscisic acid biosynthesis released the suppressing effects of 50 mM CaCl2. Taken together, these results suggest that decreased or increased protein abundance of LEA4–5, LEA4, and dehydrin might determine promoting or suppressing effects of low or high level of calcium on soybean through enhancing seed sensitivity to gibberellic acid or abscisic acid during radicle protrusion. SignificanceCalcium serves as a versatile signal in plant growth; however, calcium-mediated germination on dose-dependent manner remains elusive. In this study, dual effects of calcium on radicle protrusion in soybean were investigated using proteomic approach. Radicle growth of germinating seed was improved by 5 mM CaCl2; however, it was retarded by 50 mM CaCl2. Late embryogenesis abundant (LEA) 4–5, LEA4, and dehydrin displayed converse profiles in response to low and high concentrations of CaCl2 at both protein abundance and gene expression level. Inhibited biosynthesis of gibberellic acid (GA) significantly impeded radicle protrusion in presence of low concentration of CaCl2, while inhibiting of abscisic acid (ABA) biosynthesis released suppression induced by high concentration of CaCl2. These findings suggest that LEA proteins are associated with calcium-mediated radicle protrusion on dose-dependent manner, and seed sensitivity to GA and ABA might determine promoting and suppressing effects of calcium on radicle protrusion in soybean.

Indexes of Radicle are Sensitive and Effective for Assessing Copper and Zinc Tolerance in Germinating Seeds of Suaeda salsa

Euhalophytes, such as Suaeda salsa, are ideal candidates to remediate heavy metal-polluted saline soils. However, the metal tolerance ability of dimorphic seeds and subsequent seedlings is largely unknown. This study investigated the tolerance of S. salsa seeds to different concentrations of Cu2+ (0–300 mM) and Zn2+ (0–300 mM) during germination and seedling growth stages. Results showed that dimorphic seeds of S. salsa had high metal tolerance during germination, and even germinated under 300 mM Cu and Zn treatments. However, seedling growth was more sensitive to metal solutions and radicle growth was almost completely inhibited by Cu at 10 mM, and by Zn at 50 mM. Germinating seeds and seedlings of S. salsa had a higher metal toxicity threshold of Zn than that of Cu. In all indexes, indexes of radicle were the most sensitive and effective indicator of metal tolerance. Seeds of S. salsa germinated successfully and seedlings survived under high Zn and Cu stress. The results suggest that S. salsa could be sown directly in heavy metal-contaminated soils for phytoremediation.

Optimization of Plant Production by Seed Treatment in Two Wild Subspecies of Narcissus pseudonarcissus Rich in Alkaloids.

The daffodil Narcissus pseudonarcissus L. contains alkaloids of pharmaceutical interest. Wild daffodil populations have diverse genetic backgrounds and various genetic traits of possible importance. Developing protocols for plant production from seeds may ensure the availability of a large reservoir of individuals as well as being important for species with bulbs that are difficult to acquire. The closely related Narcissus pseudonarcissus subsp. munozii-garmendiae and subsp. nevadensis were investigated in this study because the alkaloids isolated from both are of high pharmacological interest. At the dispersal time, the seeds of both were dormant with underdeveloped embryos, i.e., morphophysiological dormancy (MPD). Experiments were conducted outdoors and under controlled laboratory conditions. Embryo growth and the percentages of radicle and seedling emergence were calculated under different temperature–light stratifications. In N. munozii-garmendiae, embryo growth occurred during warm stratification (28/14 °C or 25/10 °C) and the radicle then emerged when the temperature decreased, but the shoot was dormant. In N. nevadensis, the seeds germinated when cold stratified (5 °C) and then incubated at cool temperatures. Thus, N. munozii-garmendiae and N. nevadensis exhibit different levels of MPD, i.e., deep simple epicotyl and intermediate complex, respectively. Plant production protocols from seeds were established for both taxa in this study.

Effect of Vanadium on Testa, Seed Germination, and Subsequent Seedling Growth of Alfalfa (Medicago sativa L.)

Seed germination is the critical initial phase in the life cycle of plant and it is affected by various exogenous factors, including heavy metals. Seed germination and subsequent seedling growth of alfalfa (Medicago sativa L.) incubated in glass Petri dish in presence of elevated concentrations of pentavalent vanadium V(V) solution (0, 0.1, 0.5, 2, 4, 10, 50 mg L−1 V, supplied as NaVO3·2H2O) were evaluated. Results showed that vanadium did not (P > 0.05) affect seed germination, final survival rate, and seedling height of alfalfa when exogenously treated dosages were ≤ 10 mg L−1 V, whereas the root vitality and root elongation were distinctly inhibited at ≥ 0.5 mg L−1 V treatments. A progressively deepened testa color at increasing vanadium concentrations during germination and an apparent modified structure of the seed coat at 50 mg L−1 V compared to control in alfalfa were noted. Alfalfa seeds showed rapid and almost synchronous radicle emergence, independently of the vanadium concentration in the medium. The accumulation of vanadium in testa is beneficial to alleviate its toxicity to the seed germination of alfalfa. Leaf proline content was dramatically increased at ≥ 0.5 mg L−1 V treatments compared with the control. Emerged seedlings displayed enough vigor and health to potentially colonize in the vanadium-contained matrix. Thus, alfalfa represents a good candidate for phytoremediation approach aimed at decontaminating environments when vanadium concentrations are within the determined thresholds.

RICE SEEDLING ESTABLISHMENT AS INFLUENCED BY CULTIVARS AND SEED PRIMING WITH POTASSIUM NITRATE

Poor crop establishment is one of the major constraints to obtain the higher potential of rice, particularly in areas prone to environmental stresses. Therefore, present study was conducted to evaluate the effects of potassium nitrate on germination dynamics, seedling growth and associated physiological and biochemical events of two rice cultivars. For this purpose, various seed priming treatments were tested in lab and greenhouse. The percent concentrations of potassium nitrate were 0.25, 0.50, 0.75, 1.0 and 1.25 in both lab evaluation and greenhouse experiment. Non-primed seeds were maintained as a control for comparison. The results depicted that soaking rice seeds at higher concentrations of KNO3 could delay emergence time and final emergence (%) in both cultivars under lab and greenhouse conditions. Seed priming with 0.75% KNO3 significantly increased the stand establishment and seedling vigor attributes of both cultivars compared with other concentrations and naked rice seeds both in lab evaluation and greenhouse screening. Similarly, highest values for photosynthesis rate, evaporation rate and CO2 index were observed in experimental units receiving primed seeds with 0.75% KNO3 under greenhouse screening. Interestingly, no variance was observed among both rice cultivars. Overall, higher seed emergence, seedling vigor and associated biochemical attributes due to seed priming with 0.75% KNO3 was associated with decrease in alcohol dehydrogenase (ADH) and pyruvate decarboxylase (PDH) activities in lab and greenhouse screening.

Seed Vigour Evaluation of Rocket (Eruca sativa Mill.) Seed Lots

The work was carried out to test the seed vigour test to correlate seedling emergence potential of rocket seed lots in the field conditions. Standard laboratory germination percentages of the 12 seed lots were ranged between 87 and 93%. Radicle emergence (2 mm) percentages after 18 (RE18h), 24 (RE24h), 36 (RE36h) and 48 (RE48h) during standard germination test, accelerated ageing test (AA, 45 °C, 100% RH, 24h, 48h), electrical conductivity (20 °C, 40 ml, 50 seeds) of 8h, 16h and 24h readings were used as vigour tests. Seeds were sown in two occasions in the field and vigour test results were correlated with seedling emergence percentages. Even though all seed vigour tests were significantly correlated with emergence at various levels EC24h and RE24h showed the highest correlation (p&amp;lt;0.001) with seedling emergence percentages in both sowing times. Correlation values were 0.824 and 0.844 in EC24h, 0.860 and 0.874 in RE24h.The lowest correlations were seen in standard laboratory germination test as 0.640 and 0.654 (p&amp;lt;0.05). Results indicated that EC24h and RE24h are practical and fast vigour tests that can be related to seedling emergence potential in rocket seed lots.

Evaluation of bioherbicidal potential of Carica papaya leaves.

Due to increased number of herbicide resistant weeds, it is needed to explore the allelopathic potential of plants as an alternative. The research was conducted to investigate allelopathic effects of Carica papaya L. leaf powder and aqueous extract on seeds as well as pre-germinated seeds of Avena fatua L., Helianthus annuus L., Rumex dentatus L., Zea mays L. and Triticum aestivum L. on filter paper and soil in Weed Management Program Laboratory, Department of Plant and Environmental Protection at PARC Institute of Advanced Studies in Agriculture, National Agriculture Research Centre, Islamabad, Pakistan. Germination percentage (%), radicle length (cm) and plumule length (cm) were parameters observed for 'Plant leaf powder bioassay' and 'Aqueous extract method'. Most significant growth inhibition was observed in A. fatua seedlings in filter paper method. A. fatua radicle length was reduced by C. papaya aqueous extract (80%) and leaf powder (89%) bioassays. Plumule length was reduced under the influence of aqueous extract (57-73%) and powdered material (59-77%). The inhibitory effects on other test species were in sequence of H. annuus followed by Z. mays and R. dentatus. The aqueous extract showed non-significant effect on wheat seed germination, radicle and plumule growth. It is suggested that C. papaya aqueous extract can be used as source of weed management in wheat crop.