STUDY ON THE IN VITRO MORPHOGENETIC RESPONSE FROM SHOOT AND CALLUS CULTURES OF Blepharis maderaspatensis (L.) Heyne ex. Roth

Blepharis maderaspatensis (L.) Heyne ex. Roth is a short-term plant which contains many important secondarycompounds with high medicinal value. Currently, most of the researches focus on chemical composition and pharmacological activity, but the source of raw materials is very limited. In this study, the first step is transferring the samples from nature into in vitro culture conditions to understand the effects of the factors related to shooting and callus morphogenesis was performed, the first node from shoots apical meristem was isolated and sterilized with 1.5% NaOCl for 20 minutes to achieve high efficiency with 86.11% sterile samples and 85.56% shoot growth rate after 2 weeks of culture on MS medium. The shoot generation from axillary shoots was continued to be investigated with the highest number of shoots formed on MS medium supplemented with BA (1 mg / l) showed 1.53 shoots/implant which the height and the number of leavesare 3.65cm and 6.67, respectively. Besides, the formation of callus from leaves of MS medium supplemented with 2.4 - D (0.25 mg / l) achieved the rate of 66.67% of cultured samples, forming good callus after 4 weeks of culture. The results of the study not only contribute importantly to understanding morphogenesis for micropropagation purposes but also serve as the scientific database for further studies at the cellular and molecular levels of this plant.

Analysis of Cold-Developed vs. Cold-Acclimated Leaves Reveals Various Strategies of Cold Acclimation of Field Pea Cultivars

Peas (Pisum sativum L.) belong among the world’s oldest domesticated crops, serving as a source of proteins, complex carbohydrates, vitamins and minerals. Autumn sowing allows a higher biomass production as well as the avoidance of the drought and heat stresses of late spring. However, the character of European continental winters limits plant growth and development through cold stress. This work sought parameters that reflect the cold tolerance of pea plants and consequently to suggest an afila-type pea cultivar with resilience to European continental winters. For this purpose, we employed indoor remote sensing technology and compared the 22-day-long acclimation to 5 °C of four pea cultivars: Arkta, with normal leaves and the known highest cold resistance to European continental winters, and Enduro, Terno and CDC Le Roy, all of the afila type. Besides evaluation of shoot growth rate and quenching analysis of chlorophyll fluorescence (ChlF) by imaging methods, we measured the chlorophyll content and ChlF induction with a nonimaging fluorometer. Here we show that the acclimation to cold of the Arkta exhibits a different pattern than the other cultivars. Arkta showed the fastest retardation of photosynthesis and shoot growth, which might be part of its winter survival strategy. Terno, on the other hand, showed sustained photosynthetic performance and growth, which might be an advantageous strategy for spring. Surprisingly, Enduro showed sustained photosynthesis in the stipules, which transferred and acclimated to 5 °C (cold-acclimated). However, of all the cultivars, Enduro had the strongest inhibition of photosynthesis in new stipules that developed after the transition to cold (cold-developed). We conclude that the parameters of ChlF spatial imaging calculated as averages from whole plants are suboptimal for the characterization of various cold acclimation strategies. The most marked changes were obtained when the new cold-developed leaves were analyzed separately from the rest of the plant.

Metabolic Responses to Heat Stress under Elevated Atmospheric CO2 Concentration in a Cool-season Grass Species

Heat is a major factor limiting growth of C3 grass species. Elevated CO2 may mitigate the adverse effects of heat stress or enhance heat tolerance. The objective of this study was to determine metabolic changes associated with improvement of heat tolerance by elevated atmospheric CO2 concentration in tall fescue (Festuca arundinacea). Plants (cv. Rembrandt) were exposed to ambient day/night temperature (25/20 °C) or heat stress (35/30 °C) and ambient CO2 concentration (400 ± 10 μmol·mol−1) or double ambient CO2 concentration (800 ± 10 μmol·mol−1) in growth chambers. Turf quality (TQ), shoot growth rate, and leaf electrolyte leakage results demonstrated that heat stress at ambient CO2 concentration inhibits turf growth and reduces cell membrane stability, whereas heat-stressed plants under elevated CO2 concentration exhibit improved TQ, shoot growth rate, and membrane stability. Plants exposed to heat stress under elevated CO2 exhibited a significantly greater amount of several organic acids (shikimic acid, malonic acid, threonic acid, glyceric acid, galactaric acid, and citric acid), amino acids (serine, valine, and 5-oxoproline), and carbohydrates (sucrose and maltose) compared with heat-stressed plants at ambient CO2. The increased production or maintenance of metabolites with important biological functions such as those involved in photosynthesis, respiration, and protein metabolism could play a role in elevated CO2 mitigation of heat stress damage. Therefore, elevated CO2 conditions may contribute to improved heat stress tolerance as exhibited by better TQ and shoot growth of heat-stressed plants. Practices to harness the power of CO2 may be incorporated into turfgrass management for plant adaptation to increasing temperatures, particularly during summer months.

Morphological variability of greater yam (Dioscorea alata L.) in Malaysia

An assessment of morphological variation among 70 accessions of greater yam (Dioscorea alata L.) collected throughout Malaysia was made. Data of 47 morphological variables measured from the accessions were subjected to multivariate analysis using principal component (PCA) and cluster analysis (CA). The PCA results indicated that the characters contributing largely to the species variability were those related to the shape, size and flesh colour of underground tubers; shape and colour of aerial tubers; position, shape, size and vein colour of the leaves; petiole colour; shoot growth rate; and number of days for shoots to germinate. The two-dimensional plot of the first two PCs showed a separation between accessions of purple tuber groups and those of white tuber groups, but was unable to distinguish accessions according to tuber shape groups, i.e. irregular, oblong and round, as revealed by visual observation. The dendrogram of CA revealed four major groups of D. alata in Malaysia, which supported the PCA grouping. This study demonstrated that D. alata in Malaysia consists of numerous genotypes revealing wide inter- and intra-group variability.

Response of rock-outcrop and fringing vegetation to disturbance by fire and drought

A comparative study of vegetation responses to fire and drought investigated whether species regeneration mode, seedling density response (SDR) and seedling shoot growth rate varied significantly in relation to disturbance agent (fire and drought), habitat type (rock-outcrop and fringing vegetation) and plant growth form. A three-way ANOVA showed that SDR varied significantly in relation to all three categorical variables and most strongly in relation to disturbance agent. Seeders comprised 87% of the post-fire flora and 99.3% of the peak seedling population in rock-outcrop habitat, while resprouters were much more prominent in fringing woodland. Species SDRs and seedling growth rates were generally much higher after fire. Fire produced a high SDR with high shrub, grass and ephemeral therophyte components, and drought produced a low SDR dominated by grasses and herbs and inhibited shrub and ephemeral recruitment. Post-fire obligate-seeder shrubs behaved as facultative resprouters after drought. Some species exhibited SDRs equivalent to fire and drought, others appeared to require fire for regeneration, while others recruited more successfully after drought. This spectrum of responses indicated a range of optimal disturbance environments, depending on species, which was only partly consistent with the hypothesis that species exhibit essentially the same life-history syndromes in response to fire and drought. The dominance of seeders in outcrop vegetation appeared to be related to skeletal soil, higher disturbance frequency and soil trophic conditions, rather than low fire frequency.