Morphological and physiological responses of Dalbergia odorifera T. Chen seedlings to different culture substances.

Dalbergia odorifera T. Chen seedlings do not grow well in the typical red soils of tropical regions. Eighteen culture substances filled with different substrate combinations and proportions of red soil, coconut coir powder, deciduous leaf powder, and sand were used as to determine their effects on the growth, root system development, dry matter accumulation and allocation, leaf relative electrolyte leakage, chlorophyll content, root superoxide dismutase activity, root malondialdehyde content, and total soluble sugar content of D. odorifera. Results demonstrated that different substrate combinations and proportions had different effects on the performance of D. odorifera. All mixed substrates were better than any single substrate. The suitable substrate combinations and proportions of sand, coconut coir powder, and deciduous leaf powder mixed with red soil improved the growth, root architecture, and physiological characteristics of D. odorifera seedling. For example, groups C1-2 (coconut coir/red soil = 2/2, v/v, the same below) and C3-2 (red soil/sand = 2/2) exerted the best effects on plant growth and biomass accumulation. Groups C1-2, C2-2 (deciduous leaf powder/red soil = 2/2), and C3-2 remarkably enhanced root system development. Group C6 (coconut coir/red soil/sand = 1/1/1) substantially promoted root nodule development. Group C3-1 (red soil/sand = 3/1) exhibited the best effects on physiological characteristics. On the basis of the comprehensive evaluation of Euclid's multidimensional space mathematical model, we found that the suitable substrate combinations followed the order of C1-2 > C3-1 > C2-2. This research provides scientific guidance for the proper seedling culture of D. odorifera and the rational utilization of solid wastes such as coconut coir and deciduous leaves of Ficus elastica.

Efficient control of air pollution through plants, a cost-effective alternative: studies on Dalbergia sissoo Roxb.

Plants can be used as both passive biomonitors and biomitigators in urban and industrial environments to indicate the environmental quality and to ameliorate pollution level in a locality. Many studies reveal that plants are negatively affected by the ambient levels of air pollutants. The present study was conducted to evaluate the impact of air pollution on comparative basis with reference to changes in photosynthetic pigments, plant height, leaves, as well as, biochemical parameters of plants of different sites around Udaipur city receiving varying levels of pollution load. The investigated tree species Dalbergia sissoo Roxb. (Family: Fabaceae) exhibited a reduction in various physiological and biochemical growth parameters that correspond with air pollution levels at different sites. The tree species growing in polluted and control areas were compared with respect to foliar dust load, leaf area, and chlorophyll and total carbohydrate and total protein concentration in the leaves. Our studies suggest that D. sissoo Roxb. can successfully be grown in an area for monitoring air pollution, where it is mild and droughts are common. It will prove as an ideal tree species to control pollution effectively beside acting as a shade tree and being a source of food for birds and animals. By plantation of D. sissoo Roxb., mitigative measure at the polluted sites to control generation of particulate matter and the air quality required can be ensured. Our results also confirm that industrial and vehicular air pollution level in Udaipur city is shifting beyond limits.

Heat shock effects on seed germination of five Brazilian savanna species.

Fire is considered an important factor in influencing the physiognomy, dynamics and composition of Neotropical savannas. Species of diverse physiognomies exhibit different responses to fire, such as population persistence and seed mortality, according to the fire frequency to which they are submitted. The aim of this study is to investigate the effects of heat shocks on seed germination of Anadenanthera macrocarpa (Benth.) Brenan, Dalbergia miscolobium Benth., Aristolochia galeata Mart. & Zucc., Kielmeyera coriacea (Spreng.) Mart. and Guazuma ulmifolia Lam., which are native species of the Brazilian savanna. The temperatures and exposure times to which the seeds were submitted were established according to data obtained in the field during a prescribed fire: 60 °C (10, 20 and 40 min), 80 °C (5, 10 and 20 min) and 100 °C (2, 5 and 10 min). Untreated seeds were used as controls. Seeds of A. galeata and K. coriacea showed high tolerance to most heat treatments, and seeds of A. macrocarpa showed a significant reduction in germination percentage after treatments of 80 °C and 100 °C. Treatments of 100 °C for 10 min reduced germination percentage for all species except G. ulmifolia, which has dormant seeds. For this species, germination was accelerated by heat treatments. The high temperatures applied did not interfere with the time to 50% germination (T(50) ) of the tolerant seeds. Seeds of the savanna species K. coriacea and A. galeata were more tolerant to heat shocks than seeds of the forest species A. macrocarpa. Guazuma ulmifolia, the forest species with seeds that germinate after heat shock, also occurs in savanna physiognomies. Overall, the high temperatures applied did not affect the germination rate of the tolerant seeds.

Nodulation of Aeschynomene afraspera and A. indica by photosynthetic Bradyrhizobium Sp. strain ORS285: the nod-dependent versus the nod-independent symbiotic interaction.

Here, we present a comparative analysis of the nodulation processes of Aeschynomene afraspera and A. indica that differ in their requirement for Nod factors (NF) to initiate symbiosis with photosynthetic bradyrhizobia. The infection process and nodule organogenesis was examined using the green fluorescent protein-labeled Bradyrhizobium sp. strain ORS285 able to nodulate both species. In A. indica, when the NF-independent strategy is used, bacteria penetrated the root intercellularly between axillary root hairs and invaded the subepidermal cortical cells by invagination of the host cell wall. Whereas the first infected cortical cells collapsed, the infected ones immediately beneath kept their integrity and divided repeatedly to form the nodule. In A. afraspera, when the NF-dependent strategy is used, bacteria entered the plant through epidermal fissures generated by the emergence of lateral roots and spread deeper intercellularly in the root cortex, infecting some cortical cells during their progression. Whereas the infected cells of the lower cortical layers divided rapidly to form the nodule, the infected cells of the upper layers gave rise to an outgrowth in which the bacteria remained enclosed in large tubular structures. Together, two distinct modes of infection and nodule organogenesis coexist in Aeschynomene legumes, each displaying original features.

Stimulation of cyclic electron flow during recovery after chilling-induced photoinhibition of PSII.

Although cyclic electron flow (CEF) is essential for repair of PSII, it is unclear whether the CEF is stimulated and what the role of stability of PSI is during the recovery. In order to explore these two questions, mature leaves of Dalbergia odorifera were treated with the chilling temperature of 4°C under a photosynthetic flux density (PFD) of 650 µmol m(-2) s(-1) for 2 h and then were transferred to 25°C under a PFD of 100 µmol m(-2) s(-1) for recovery. The maximum quantum yield of PSII (F(v)/F(m)), the maximum photo-oxidizable P700 (P(m)), the energy distribution in PSII and the redox state of P700 at 25°C under a PFD of 100 µmol m(-2) s(-1) were determined before and after chilling treatment and during subsequent recovery. We found that the CEF was significantly stimulated during the recovery after photodamage. There is a significant positive correlation between stimulation of CEF and photodamage of PSII during recovery. Our results indicated that CEF was significantly stimulated in order to enhance the synthesis of ATP for the fast repair of PSII. The stability of PSI activity favored the fast repair of PSII activity through stimulation of CEF.

Aluminium tolerance and high phosphorus efficiency helps Stylosanthes better adapt to low-P acid soils.

BACKGROUND AND AIMS: Stylosanthes spp. (stylo) is one of the most important pasture legumes used in a wide range of agricultural systems on acid soils, where aluminium (Al) toxicity and phosphorus (P) deficiency are two major limiting factors for plant growth. However, physiological mechanisms of stylo adaptation to acid soils are not understood. METHODS: Twelve stylo genotypes were surveyed under field conditions, followed by sand and nutrient solution culture experiments to investigate possible physiological mechanisms of stylo adaptation to low-P acid soils. KEY RESULTS: Stylo genotypes varied substantially in growth and P uptake in low P conditions in the field. Three genotypes contrasting in P efficiency were selected for experiments in nutrient solution and sand culture to examine their Al tolerance and ability to utilize different P sources, including Ca-P, K-P, Al-P, Fe-P and phytate-P. Among the three tested genotypes, the P-efficient genotype 'TPRC2001-1' had higher Al tolerance than the P-inefficient genotype 'Fine-stem' as indicated by relative tap root length and haematoxylin staining. The three genotypes differed in their ability to utilize different P sources. The P-efficient genotype, 'TPRC2001-1', had superior ability to utilize phytate-P. CONCLUSIONS: The findings suggest that possible physiological mechanisms of stylo adaptation to low-P acid soils might involve superior ability of plant roots to tolerate Al toxicity and to utilize organic P and Al-P.

Mineral accumulation, growth, and physiological functions in Dalbergia sissoo seedlings irrigated with different effluents.

Present study aimed to observe the mineral accumulation added through effluent application and their influence on physiological functions and growth of Dalbergia sissoo and ultimately to find out suitable combination of industrial and municipal effluent for their utilization in raising tree plantation. Dalbergia sissoo seedlings were irrigated with: canal water (T1); municipal effluent (T2); textile effluent (T3); steel effluent (T4); textile + municipal effluent in 1:1 ratio (T5); steel + municipal effluent in 1:2 ratio (T6); steel + municipal + textile in 1:2:2 ratio (T7); and steel + textile in 1:2 ratio (T8). Mineral accumulation, water relations and gas exchange, growth and biomass production were the recorded observations. Mortality occurred within a day for the seedlings in T4, 45 days in T6, and 60 days in T7 and T8 treatments. This was probably the result of high (P<0.01) Mn, Fe, Cu, and Zn and low N, P, K, Ca, and Mg concentration in different parts of the seedlings in these treatments affecting physiology and growth. Reduction in rate of photosynthesis (Pn) and transpiration (T) to the level of 90%, leaf water potential (LWP) and increased stomatal resistance (R) at two months of age is the indicator of metal toxicity in these treatments. Pn and T were 20 and 17% high in T2 treatment, respectively. However, the reduction was only 21 and 10% in Pn and 18 and 26%, respectively in the seedlings of T3 and T5 than that in T1 treatment. During nine months of observation, the seedlings of T2 and T5 maintained high LWP and same rate of Pn and T but they reduced significantly (P<0.01) in the seedlings of T3 treatment affecting biomass production. This was believed to be due to increase in Na concentration leading to decrease in Mg, Ca, Mn, Fe, Cu and Zn concentration and ratio of Mg/Na and Mg/K and increased ratio of N/Mg and K/Ca + Mg. The enhanced physiological functions in T5 treatment were probably the result of ameliorative effect of municipal effluent through increased mineral status producing biomass equivalent to that in T1 treatment at 10 months of age. The seedlings of T2 attained greater (P<0.01) height and collar diameter and produced 120g seedling(-1) of dry biomass. The study suggests that addition of excess mineral elements leads to metal toxicity that adversely affects physiology and ultimately growth and productivity of tree seedlings. Mixing of effluents to ameliorate the toxic effects could be the better management practices for their use in tree irrigation.