Maximum Shoot Growth Research Articles

Sugarcane Demands Lower Nitrogen Supply to Sustain Mesophyll Chloroplast Integrity than Maximum Shoot Growth

Sugarcane Demands Lower Nitrogen Supply to Sustain Mesophyll Chloroplast Integrity than Maximum Shoot Growth

Caracteres morfológicos que contribuem para o aumento da produtividade de cultivares de batata no Brasil

ABSTRACT A previous study revealed that modern potato cultivars used in Brazil have higher commercial tuber yield than old cultivars. The objective of the present study was to clarify which morphological characters influence the yield gain of modern cultivars. Two field experiments were performed in Brazil: in Guarapuava-PR and Brasilia-DF. The treatments consisted of six cultivars, classified according to origin and year of release: Bintje (European, 1910), Baronesa (Brazilian, 1955), Monalisa (European, 1982), Agata (European, 1990), Catucha (Brazilian, 1995) and BRS Clara (Brazilian, 2010). These were the main cultivars used in southern Brazil in the last 65 years and represent 100 years of breeding. A randomized complete block design with six treatments and four replications was used. The following plant morphological characters were evaluated at four growth stages (the beginning of plant development, the beginning of tuberization, maximum shoot growth and tuber bulking stages): leaf area index, specific leaf area, number of main stems, initiated and bulked tubers. At 15 days after emergence, modern cultivars have higher leaf area index and bulked tubers compared to older cultivars. Also, a larger number of mainstems and smaller specific leaf area were observed in modern cultivars. A high leaf area index at the beginning of the growing development combined with a large number of bulked tubers contributed to the increase of the yield potential of modern cultivars.

Effect of plant growth regulator, applin on growth, yield and quality of royal delicious apple

Fruit size is one of the important quality parameters of apple to enhance the economic value in terms of yield and consumers preference. In the year of heavy crop load of apple tree, the fruit remains undersized which reduces the market value after harvesting. To overcome this problem, the use of gibberellins and cytokinins plant growth regulators to maintain the proper size of fruits under heavy crop load is an alternative way. The present study was carried out to know the effect of Applin (gibberellin and cytokinin) on growth, yield and quality of Royal Delicious apple. Maximum shoot growth, fruit length, fruit diameter, fruit weight, yield and ascorbic acid content were recorded in plants treated with 0.5 ml/l of Applin and with 1.0 ml/l of Wetcit. The overall results of this study showed that the application of plant growth regulator at the concentration significantly increased the size, quality and shelf-life of apple during the year of high crop load.

Potential Use of Ascophyllum nodosum as a Biostimulant for Improving the Growth Performance of Vigna aconitifolia (Jacq.) Marechal.

The fertilizers that are derived from seaweed are known as Seaweed Liquid Fertilizers (SLF). SLF is a modern, cheap, non-toxic, and natural bioactive fertilizer. Among different studied seaweeds, Ascophyllum nodosum is significant as having bioactive ingredients that potentially regulate the molecular, physiological, and biochemical processes of crop plants. In the present study, the effects of the application of different concentrations (0.00%, 0.01%, 0.02%, 0.05%, 0.10%, 0.50%, and 1.00%) of A. nodosum Extract (ANE) to the Vigna aconitifolia through roots (Pot Root Application, PRA) and on the leaves (Pot Foliar Application, PFA) were monitored via the plant growth. The lower concentrations of ANE in both the PRA and PFA experiments showed positive growth on V. aconitifolia. The 0.10% ANE stimulated the maximum shoot growth when applied through the roots, while 0.05% ANE in both PFA and PRA experiments led to an increase in the number of pods, nodules, organic content, and moisture percentage. The 0.10% ANE also increased the leaf numbers, leaf area, and photosynthetic pigments. Hence, the application of 0.05% and 0.10% of A. nodosum extract in two ways (i.e., Pot Foliar Application, PFA, and Pot Root Application, PRA) ameliorated the growth capabilities of V. aconitifolia.

Effect of leaf thinning on shoot growth and tuber yield of white Guinea yam

ABSTRACT Mutual leaf shading can inhibit the growth of yam, reducing tuber yield. To improve light utilization, approximately 25% of leaves in a plant were thinned during the period of maximum shoot growth. Shoot dry weight was estimated every two weeks using a non-destructive method. Leaf thinning caused higher shoot growth rates (SGRs) after thinning, while control plants had SGRs close to zero. The higher SGRs in the thinned plants was attributed to an increase in new leaf development. This indicates that the plateau in shoot growth commonly observed during the late growth period is reversible and could be improved artificially. In thinned plants, there was a positive relationship between shoot dry weight and SGR, although no such relationship was observed in control plants after the middle growth period. This positive correlation indicates a higher shoot growth per unit leaf area in the thinned plants than in the control plants, presumably due to improved light utilization and a higher photosynthetic rate of new leaves. However, leaf thinning reduced tuber yields, presumably because of a lower total carbon assimilation per plant and greater growth competition between shoots and tubers. High correlations between shoot dry weight and tuber yield indicated that a high shoot biomass is more important than improving light utilization for increased tuber yields.

Micropropagation of Philodendron selloum: Influence of copper sulfate on endophytic bacterial contamination, antioxidant enzyme activity, electrolyte leakage, and plant survival

Endophytic microorganisms is a major constrain to the establishment and growth of tissue culture plants. We report the use of copper sulfate (CuSO4.5H2O) to eliminate the endophytic bacteria in Philodendron selloum in vitro cultures. Contaminated shoots were cultured onto Murashige and Skoog (MS) medium containing 5 mg/L BA and supplemented with different concentrations of copper sulfate at 0, 35, 70 and 140 mg/L for 6 weeks. Copper sulfate at 70 mg/L completely eliminated the endogenous bacteria without decline in plant growth. However, 35 mg/L copper sulfate was optimal for maximum shoot multiplication (25), survival percentage (100%) and growth of plants. Antioxidant enzymes activity of catalase, peroxidases, and polyphenol oxidase were increased because of copper sulfate treatments. Conversely, electrolyte leakage was decreased at low copper sulfate (≤70 mg/L). Randomly amplified polymorphic DNA (RAPD) analysis revealed that plantlets exposed to different levels of copper sulfate were not genetically different from control plants.

Nitrogen and Potassium Fertilisation Influences Growth, Rhizosphere Carboxylate Exudation and Mycorrhizal Colonisation in Temperate Perennial Pasture Grasses

Optimisation of potassium (K) use efficiency in pastures on sandy soil is challenging. We characterised growth response, root carboxylate exudation and mycorrhizal colonisation in three perennial pasture grasses: tall fescue (Festuca arundinacea L.), veldt grass (Ehrharta calycina Sm.) and tall wheatgrass (Thinopyrum ponticum L.) in two glasshouse experiments with: (1) four K rates (0, 40, 80 and 120 mg K kg-1 soil), and (2) four N and K treatments (no N and K (–N–K), 81 mg N kg-1 soil but no K, 80 mg K kg-1 soil but no N, and N at 81 and K at 80 mg kg-1 soil (+N+K)) in low-K sandy soil. Veldt grass had the highest shoot dry weight and shoot P content, but the lowest mycorrhizal colonisation. Potassium fertilisation had no significant impact on exudation of citrate and oxalate. The K0 plants had significantly lower exudation of acetate and total carboxylates than K40 plants. The +N+K plants had maximum shoot growth at both harvests (30 and 60 days after sowing (DAS)) and highest N and K shoot contents at 60 DAS. The –N–K plants exuded maximum amounts of citrate and malate at 30 DAS, but at 60 DAS tall fescue had the highest rhizosphere concentrations of citrate and malate in the +N+K treatment. At 60 DAS, mycorrhizal colonisation was significantly lower with than without N and K fertilisation. We concluded that pasture grasses could yield well even in inherently low-K soil without external K fertilisation and mycorrhizal symbiosis. However, the +N+K plants had the highest yield and root carboxylate exudation.

MICROPROPAGATION OF YUCCA PLANT BY USING GUAR AND LOCUST BEAN SEED POWDER AS AN ALTERNATIVE CHEAP GELLING AGENT

The present study aims to determine the best type and concentration of growth regulators and find cheap and/or readily-available alternative substitutes of agar for tissue culture media preparation. The results clear that MS medium supplemented with 1 mg l-1 BA significantly outperformed other tested cytokinins concerning yucca shoot multiplication and growth parameters (number of shoots/explant, number of leaves/shoot, and shoot length (cm)) which recorded 4.75, 14.00 and 6.50 cm, respectively. Moreover, the combination between 2 g l-1 agar and 6 g l-1 guar as gelling agents produced the maximum shoot growth values. During rooting stage, data clear that 1.0 mg l-1 NAA increased number of leaves/shoot, number of roots/shoot and root length with mean values of 20.50, 3.75 and 5.22 cm, respectively. Finally, rooted plantlets were successfully acclimatized with maximum survivability percentage (100%) in soil mixture of sand and peat moss (1:1. v/v).

Forage biomass yield and arbuscular mycorrhizal symbiosis in a legume and C3 and C4 grasses under increasing soil phosphorus availability

Phosphorus (P) is the main limiting factor for forage production in grasslands. It is important to determine levels of available P in soil that optimise production with minimum impact on arbuscular mycorrhizal (AM) symbiosis. We investigated the effects of increasing P availability on biomass production, root morphology, AM symbiosis and P acquisition of a forage legume (Lotus tenuis), a C3 grass (Schedonorus arundinaceus) and a C4 grass (Panicum coloratum) growing on a P-deficient soil in pots with P applied at rates of 0–160 mg kg–1 dry soil. The three forage species responded strongly to addition of P, with 90% of maximum shoot growth reached at available P levels of 24.3 mg kg–1 for L. tenuis, 14.4 mg kg–1 for P. coloratum and 11.2 mg kg–1 for S. arundinaceus. Lotus tenuis and P. coloratum produced higher yields of shoot biomass than S. arundinaceus. Root dry weight was higher in the legume than in the grasses, with the root-mass fraction being lowest in P. coloratum. AM colonisation was higher in L. tenuis roots than in grass roots, and decreased with increased soil P availability, especially in grasses. Low to moderate additions of P did not affect, and could even improve, AM colonisation in L. tenuis roots. For L. tenuis, it is possible to increase forage yield while maintaining high values of AM colonisation at 10–20 mg kg–1 of available P, but for grasses, especially S. arundinaceus, it is difficult to achieve both objectives. The presence of L. tenuis in grasslands or pastures may contribute to maintaining the native AM inoculum under a wide range of soil P availability in regions such as the Salado River basin of Argentina.

Biotic strategies to increase plant availability of sewage sludge ash phosphorus

AbstractSewage sludge incineration‐ash (FB‐I) represents a potential alternative phosphorus (P) fertiliser with a high concentration of P, although with relatively low crop availability. In this study, we investigated two P‐solubilisation approaches (acidification and P mobilisation by citrate) to enhance plant P uptake from the FB‐I ash in a pot study by using various biotic strategies: (1) a pre‐treatment of ash with a Penicillium bilaiae inoculum, (2) an isogenic line of wheat that excretes citrate from the root tip, (3) nitrogen (N) provided as combined with nitrification inhibitor dicyandiamide (DCD). All strategies were tested combined with each other and with different methods for ash application: (1) completely mixed within the top one third of soil in a pot, or (2) applied as distinct band at 10 cm depth. Triple super phosphate (TSP) at a rate of 15 mg P kg−1 soil per pot was sufficient to support maximum shoot growth. Ash mixed into the first top third part of soil in the pot at a rate of 180 mg P kg−1 soil (equivalent to 60 mg P kg−1 soil throughout the pot) significantly increased the soil water‐extractable P and the subsequent shoot P uptake and shoot biomass for both wheat lines and microbial pre‐treatment to support maximum plant performance. Shoot P concentration in these treatments was further enhanced when the plants received and DCD, although not leading to a significant increase in shoot biomass. The citrate secretion by the root tips and pre‐inoculation with P. bilaiae of the ash did not influence plant growth. In conclusion, root‐zone soil acidification by nutrition is regarded as a promising strategy to improve the fertilising effect of such alternative P fertilisers originating from urban waste streams.

Effect of exogenous application of plant growth regulators on vine growth, yield and quality attributes in kiwifruit cv. Hayward

Present investigation was carried out on 11-year-old vines of kiwifruit cv. Hayward trained on a T bar trellissystem for two years. Four different plant growth regulators viz., GA3 (25 & 50 mg l−1), BA (10 & 20 mg l−1), 2, 4-D (10 & 25 mg l−1), TRIA (10 & 20 mg l−1) and a natural extract (4 g ml−1) were sprayed four weeks after full bloom. Allthe growth regulators proved effective in improving vine growth, yield and physico-chemical characteristics offruits as compared to control. Maximum shoot growth (157.27 & 153.49 cm) was observed with the applicationof 50 mg l−1 GA3. Maximum leaf area (190.25 & 188.34 cm2) was obtained with 25 mg l−1 of GA3. The highest fruitretention (86.19 & 81.06%) and yield per vine (57.98 & 54.82 kg) was recorded with 10 mg l−1 2, 4-D. Advancement in harvest maturity was noted with 10 mg l−1 TRIA. Among all the treatments, application of 25 mg l−1 GA3 followed by 10 mg l−1 2, 4-D proved to be more effective in improving fruit physical characteristics viz., fruit weight, fruit length & fruit diameter; and chemical characteristics viz., total soluble solids and total sugars.

Effect of planting density on growth, yield and fruit quality of apple cv. Jeromine

A field experiment was conducted to study the effect of different planting densities on growth, yield and fruit quality of three-years-old apple trees during 2017–2018. The experiment was laid out in a Randomized Block Design consisting of four treatments of planting densities viz., 5333 trees/ha (2.5 m × 0.75 m), 4000 trees/ha (2.5 m × 1.0 m), 3200 trees/ha (2.5 m × 1.25 m) and 2666 trees/ha (2.5 m × 1.5 m) and each treatment was replicated six times. The maximum annual shoot growth (44.58 cm) and increase in tree height (42.55 cm) was recorded in planting density of 2666 trees/ha (2.5 m × 1.5 m) which was significantly higher than all other planting densities. Highest fruit yield per tree (4.93 kg/tree) was observed in high density 2666 trees/ha (2.5 m x (17.50 tonne/ha) was recorded in planting density of 5333 trees/ha (2.5 m x 0.75 m). Maximum fruit length (65.90 mm), fruit diameter (76.07 mm), fruit weight (177.45 g), sugars content and anthocyanin content was found in planting density of 2666 trees/ha (2.5 m x 1.5 m). On the basis of two-years study, it can be concluded that the planting densities of 3200 trees/ha (2.5 m x 1.25 m) and 2666 trees/ha (2.5 m x 1.5 m) could be the optimum density for higher production of quality fruits.

Production of biomass and bioactive compounds from shoot cultures of Rosa rugosa using a bioreactor culture system

Rosa rugosa Thunb. is a popular ornamental and medicinal plant native to eastern Asia. In this study, a successful bioreactor culture system was established for the production of secondary metabolites of rugosa roses. We tested different concentrations and combinations of plant hormones in growth media for maximum shoot proliferation and production of bioactive compounds, different bioreactor systems for maximum biomass production and production of bioactive compounds, and different ratios of nitrogen sources for maximum shoot growth and accumulation of bioactive compounds. For multiple shoot proliferation, Murashige and Skoog (MS) medium was used, supplemented with different concentrations and combinations of plant hormones: 6-benzylaminopurine (BA; 0-13.2 µM), thidiazuron (TDZ; 0-13.5 µM), and indole butyric acid (IBA) at 2.5 µM, used alone or in a combination of IBA with BA or TDZ. Rapid micropropagation of multiple shoots of rugosa roses was successfully achieved using shoot tips explanted in semisolid MS medium supplemented with 4.4 µM BA. The average number of shoots grown was 15.6 per explant and the maximum shoot length was 2.7 cm at 8 weeks of culture. To investigate the effect of nitrogen sources on shoot growth and bioactive compound accumulation, shoots were treated with different ratios of nitrogen sources (NH4+:NO3-) for 1 week after 7 weeks of shoot culture. Next, to scale up biomass production for the generation of useful phytochemicals, multiple-shoot cultures were developed in large-scale bioreactors. Four bioreactor systems were used: continuous immersion bioreactor (CIB), continuous immersion bioreactor with net (CIB-N), temporary immersion bioreactor (TIB), and temporary immersion bioreactor with net (TIB-N). Solid and liquid media were used as controls. Of the different bioreactor types, the CIB system produced the highest biomass, followed by the TIB system. Multiple shoots grown in the CIB system resulted in the accumulation of 39.21 mg·g-1 dry weight (DW) of total phenolics and 13.28 mg·g-1 DW of total flavonoids. The productivity of total phenolics and flavonoids was highest in the shoots harvested from the CIB system. The results of this study suggest that multiple shoots of rugosa roses can be used in commercial-scale bioreactors to produce useful bioactive compounds for the pharmaceutical and cosmetic industries.

Phosphorus Nutrition of Upland Rice, Dry Bean, Soybean, and Corn Grown on an Oxisol

Rice, dry bean, corn, and soybean are important food crops. Phosphorus (P) deficiency is one of the most yield-limiting factors for these crops grown on highly weathered Brazilian Oxisols. Four greenhouse experiments were conducted to determine P requirements of these four crops. The P levels used were 0, 50, 100, 200, and 400 mg kg−1. Growth, yield, and yield components evaluated of four crop species were significantly increased with the application of P fertilization. Most of the responses were quadratic in fashion when the P was applied in the range of 0 to 400 mg kg−1. Maximum grain yield of upland rice was obtained with the application of 238 mg P kg−1 of soil, maximum dry bean grain yield was obtained with the application of 227 mg P kg−1 of soil, and maximum grain yield of soybean was obtained with the application of 224 mg P kg−1 of soil. Maximum shoot growth of corn was obtained with the addition of 323 mg P kg−1 of soil. Most of the growth and yield components had significant positive association with grain yield or shoot dry weight. Phosphorus concentration and uptake were greater in the grain compared to straw in upland rice and dry bean plants. Overall, P-use efficiencies decreased with increasing P rates.

High-frequency clonal propagation, encapsulation of nodal segments for short-term storage and germplasm exchange of Ficus carica L.

The study describes an efficient regeneration system and encapsulation of nodal segments in F. carica accompanied with frequent root formation in microshoots under the influence of salicylic acid. The present study describes an improved protocol for clonal propagation and a short-term conservation strategy using an encapsulation technology for Ficus carica. Nodal segments were more responsive than shoot tips for shoot multiplication. Among the cytokinins tested, Murashige and Skoog’s (MS) medium augmented with 7.5 µM 6-benzyladenine (BA) was the best, but the leaves exhibited a rudimentary structure. Cytokinin–auxin combinations enhanced the multiplication rate; but leaf growth did not improve. However, the supplementation of 50 µM adenine sulphate (Ads) to MS + 7.5 µM BA + 0.5 µM α-naphthalene acetic acid (NAA) significantly enhanced mean shoot number per explant and overall growth of shoots and induced a maximum of 26.8 shoots per nodal segment and 15 shoots per shoot tip with mean shoot length of 8 and 4.3 cm, respectively, after 4 weeks of culture. Microshoots rooted on half-strength MS medium containing 2.5 µM salicylic acid (SA) either in semi-solid (mean of 4.6 roots per shoot) or liquid medium (mean of 5 roots per shoot). A gelling matrix of 4 % sodium alginate (Na-alginate) and 100 mM calcium chloride (CaCl2·2H2O) was used for the encapsulation of nodal segments. Maximum shoot growth (95.6 %) was recorded on MS medium supplemented with 7.5 µM BA + 0.5 µM NAA + 50 µM Ads. Rooting was induced upon transfer of sprouted microshoots to semi-solid half-strength MS medium supplemented with 2.5 µM SA. To examine the retention of encapsulated and non-encapsulated nodal segments’ viability, a low-temperature storage (4 °C) experiment was carried out. Encapsulated nodal segments stored at 4 °C for 1–6 weeks sprouted at variable frequencies in successive weeks of transfer. Plantlets were acclimatized and established in field where they grew without any detectable variations after 6 months of transfer.

Heading cuts and prohexadione-calcium affect the growth and development of ‘d’Anjou’ pear shoots in a high-density orchard

Prohexadione calcium (P-Ca) has been shown to effectively reduce the vigor of pear trees. However, an analysis of the effects of P-Ca on growth and development of headed and unheaded shoots has not been performed. Therefore, P-Ca was selectively applied to dormant-headed (1/3rd removed) and unpruned shoots in a high-density ‘d’Anjou’ pear orchard in Oregon, USA. Both sets of shoots were treated with 250mgL−1 P-Ca in either a single or double application and compared to controls. The first application was delivered to shoots when ∼5cm of new growth accrued; the second, only if shoot growth resumed. P-Ca reduced shoot growth of both headed and unpruned shoots relative to their respective controls. Growth of unpruned shoots ceased 3 weeks following the first P-Ca application. In contrast, headed shoots required 6 weeks from the initial application to cease elongating. A markedly higher maximum shoot growth rate (mmd−1) was observed for headed shoots treated with P-Ca compared to unpruned shoots treated with P-Ca. At 87 days after full bloom, P-Ca-treated, unpruned shoots had a pronounced second flush of growth requiring an additional application of P-Ca. This growth resumption was 2 weeks earlier than unpruned, control shoots and 17d earlier than P-Ca-treated, headed shoots, for which only a negligible growth flush was observed. At the end of the season, unpruned shoot length was decreased by 28% and 41% for shoots treated with P-Ca once or twice, respectively, while headed shoots were 37% shorter than their controls (treated only once). The number of nodes and average internode length were significantly reduced for P-Ca-treated shoots, irrespective of pruning level, conferring a higher node density relative to control shoots. An increase in node density should result in higher yield efficiency once fruiting occurs on this wood. Heading, in contrast, increased the internodal space and decreased the number of nodes, ultimately decreasing node density. We did not observe any physiological effects on the growth or development of adjacent, untreated shoots originating from identical scaffolds as P-Ca-treated shoots. Collectively, these results implicate P-Ca as a powerful tool for precision-management of tree vigor in intensive pear plantings via selective treatment to areas of high vigor.

Phytotoxicity assessment of γ-Fe2O3 nanoparticles on root elongation and growth of rice plant

This study was conducted to determine the phytotoxicity of 6 nm γ-Fe2O3 nanoparticles (IONPs) in terms of root elongation and the physiological performance of rice plants. Rice seeds (Oryza sativa L. var. Koshihikari) exposed to IONPs at 500, 1,000 and 2,000 mg/L, had a significantly higher root elongation than the control and its bulk counterparts (IOBKs), indicating that the effect can be nanospecific. In a 14-week greenhouse pot experiment, the CO2 assimilation rate in IOBK and IONP-treated pots (500 and 1,000 mg/pot) decreased over time, with the decline (maximum 42.5 %) being less pronounced for IONPs, indicating that the effect cannot be inferred from the toxicity of nanoscale size iron oxide. Excessive adsorption of IONPs onto soil colloids with subsequent low water extractable iron was responsible for the unremarkable phytotoxic nature of IONPs in the rice plants. Amendment of IONPs coated with 20 mmol citric acid (IONPs-Cit) significantly diminished the CO2 assimilation rate and the decrease was similar to its bulk counterpart (IOBKs-Cit). However, maximum shoot growth inhibition (37 %) was associated with the application of IOBKs-Cit. It was concluded that massive accumulations of Fe plaque on the root surfaces of IOBKs-Cit treatments due to a decline in the pH of rhizoplane soils compared to the IONPs-Cit treatments were responsible for the remarkable shoot growth reduction. This study provided evidence of the phytotoxicity of γ-Fe2O3 nanoparticles, demonstrating the lower toxicity of nanosized iron oxide compared to a microsized preparation under reductive conditions.

Relationships between seedling establishment and soil moisture content for winter and spring rapeseed genotypes

Rapeseed cultivars are important for edible oil production under semiarid area regions in Iran. However, germination and seedling establishment of rapeseed cultivars are the critical steps in successful production of this oil crop plant that are not well understood. The objective of this study was to evaluate the effect of low soil moisture on emergence and seedling establishment of 24 rapeseed genotypes including 13 cultivars and 11 doubled haploid lines. A pot experiment was conducted in a greenhouse using a factorial experiment based on a completely randomized design with three replications. The genotypes were evaluated under different soil field capacity (FC) levels (80%, 50%, 30% and 20% FC). Decreasing the soil moisture content from 50% to 20% FC resulted in reduced overall final emergence from 94.3% to 82.7%. Significant differences were observed among genotypes under different soil moisture levels for all studied characters. Seedling vigor index and shoot growth of the tolerant genotypes were significantly higher under lower soil moistures levels. Studies on identification indices of drought resistance by principal component analysis (PCA) indicated that germination rate and final emergence were most important and better indicators of establishment in rapeseed. Cluster analysis and PCA method separated the genotypes into four groups. Genotypes in group I had the greatest tolerance, cluster II the intermediate tolerance, and clusters III and IV had the least tolerance to low soil moisture. In response to low soil moisture, cluster I (included GKH2005, Opera and Okapi) showed higher final emergence, rapid emergence, strong seedling vigor, and maximum shoot growth. On the other hand, cluster II (included DH1, DH3, DH4, DH5, DH7, DH8, DH9, DH10, DH11 and DH13) showed high coefficient of germination rate. Cluster III (included Cooper, SLM046, Lilian, Billy and Karun) had greater root length, cotyledon length and width, and root-to-shoot length with high mean time to germination whereas decreasing soil moisture resulted in severe reductions of final emergence and germination rate compared with those observed for 80% and 50% FC. Also, cluster IV (Included Adriana, Oase, Savanah, Triangle, Tasilo and DH6) had lower final emergence, delayed emergence, low growth potential, and high sensitivity for shoot and root growth. The results suggest that the genetic diversity within cluster I could be used for crop breeding programs and increasing the cultivation area in arid and semiarid regions of Iran.

Effect of Auxins on Shoot and Root Growth in an Endangered Medicinal Plant Guggal [Commiphora wightii (Arnott.) Bhand.

An investigation was carried out to study the effect of IBA and NAA on vegetative propagation of guggal[Commiphora wightii (Arnott.) Bhand.] through cuttings, at Navsari Agricultural University, Navsari. The experiment consists of ten treatments: IBA, NAA and their combination, each at 2000, 4000 and 6000 mg l-1along with control, replicated thrice. Ten cuttings per each treatment and per replication were planted. Planting media used were: sand, soil and vermicompost, in 2:1:1 ratio. Cuttings were dipped for five minutes in solutions of IBA, NAA and their combinations. Cuttings treated with 4000 mg l-1 IBA proved to be the best for shoot and root responses, viz., days taken to first sprouting (11.67 days), number of shoots per cutting (10.27), number of leaves in the longest shoot (44.07), length of longest shoot (51.69cm), diameter of the longest shoot (4.40mm), rooting percentage (61.19), number of primary roots per cutting (15.01), length of the longest primary root (26.36cm), and number of secondary roots (22.37) and length of the longest secondary root (21.40cm) per cutting. It was concluded that IBA @ 4000 mg l-1 was most effective for obtaining maximum shoot and root growth.

Plant responses to heterogeneous salinity: growth of the halophyte Atriplex nummularia is determined by the root-weighted mean salinity of the root zone.

Soil salinity is generally spatially heterogeneous, but our understanding of halophyte physiology under such conditions is limited. The growth and physiology of the dicotyledonous halophyte Atriplex nummularia was evaluated in split-root experiments to test whether growth is determined by: (i) the lowest; (ii) the highest; or (iii) the mean salinity of the root zone. In two experiments, plants were grown with uniform salinities or horizontally heterogeneous salinities (10–450mM NaCl in the low-salt side and 670mM in the high-salt side, or 10mM NaCl in the low-salt side and 500–1500mM in the high-salt side). The combined data showed that growth and gas exchange parameters responded most closely to the root-weighted mean salinity rather than to the lowest, mean, or highest salinity in the root zone. In contrast, midday shoot water potentials were determined by the lowest salinity in the root zone, consistent with most water being taken from the least negative water potential source. With uniform salinity, maximum shoot growth was at 120–230mM NaCl; ~90% of maximum growth occurred at 10mM and 450mM NaCl. Exposure of part of the roots to 1500mM NaCl resulted in an enhanced (+40%) root growth on the low-salt side, which lowered root-weighted mean salinity and enabled the maintenance of shoot growth. Atriplex nummularia grew even with extreme salinity in part of the roots, as long as the root-weighted mean salinity of the root zone was within the 10–450mM range.