A. H. Abad Farooqi

Regulation of essential oil production in plants

This review provides a summary of the physiological dynamics andregulation of essential oil production, from the literature and availableinformation on diverse volatile oil crops. Essential oil production is highlyintegrated with the physiology of the whole plant and so depends on themetabolic state and preset developmental differentiation programme of thesynthesising tissue. Essential oil productivity is ecophysiologically andenvironmentally friendly. These and other aspects of the modulation ofessentialoil production are presented, along with a brief outline of the current conceptof the relevant biosynthetic mechanisms.

Effect of triacontanol and chlormequat on growth, plant hormones and artemisinin yield in Artemisia annua L

Artemisinin and herbage yield of Artemisia annua plants were determined after application of triacontanol (tria.) and chlormequat (2-chloroethyltrimethylammonium chloride). Tria. at 1.0 and 1.5 mgl−1 produced a statistically significant positive effect on artemisinin level as well as on plant height, leaf and herbage yield. Chlormequat at 1000 and 1500 mgl−1 also increased artemisinin level, decreased the plant height at higher concentrations and increased the leaf and herbage yield at lower concentrations. Tria. application enhanced GA-like activity, but ABA levels decreased, while chlormequat increased ABA but reduced GA-like substances. The effect of Tria. on artemisinin yield seems to be mediated through its effect on plant growth.

Effect of different photoperiodic regimes on growth, flowering and essential oil in Mentha species

Three major cultivated Mentha spp. (M. arvensis, M. citrata and M. cardiaca) were grown under short-days, normal-days or long-days for 60 cycles. Subsequent to photoperiodic treatment, the plants were assessed for growth behaviour, essential oil content, oil composition and essential oil biosynthesis. The species grew better under long-day conditions. The long-day treatment resulted in flowering in M. citrata, which normally does not flower under our conditions. The oil concentration and biogenesis was maximal in short-day plants. The photoperiodic treatment also affected the oil composition. The observations are discussed in relation to physiology of the oil biogenesis.

Interspecific Variation in Physiological and Metabolic Responses of five Species of Cymbopogon to Water Stress

Summary The effect of drought on physiological and biochemical responses viz. Ψ, RWC, plasma membrane damage, accumulation of proline, induction of PEP carboxylase activity and essential oil biosynthesis in five species of Cymbopogon (family poaceae) was investigated. The species differed considerably in their response to water deficit. A dramatic increase in PEP carboxylase activity was observed in all of the cases; however, oil biosynthesis under drought increased in C. martinii and C. pendulus while it decreased substantially in C. flexuosus . Its level remained almost the same in C. nardus and C. winterianus . The effect of drought appears to be species specific. The physiological significance of PEP carboxylase induction and the effect of stress on oil biogenetic capacity are discussed.

Effect of growth retardants on growth and essential oil content in Japanese mint

In field experiments with Japanese mint using different growth retardants, chlormequat chloride (2-chloroethyltrimethylammonium chloride) increased the oil content significantly and inhibited growth to some extent only, whilst ethephon (2-chloroethyl phosphonic acid) at 0.06% concentration significantly decreased growth but had no significant effect on oil content. Among the two oil components studied, menthone content only was significantly increased by 0.06% ethephon whereas the other growth retardants were ineffective. Correlation studies indicated a strong negative relationship of leaf/stem ratio with plant height and herb yield while a strong positive relationship was obtained between the latter two characters. The oil content of the plant was negatively correlated with herb yield and plant height but it was related positively with leaf/stem ratio.

Interspecific Variation in Sodium and Potassium Ion Accumulation and Essential Oil Metabolism in Three Cymbopogon Species Raised under Sodium Chloride Stress

Abstract Responses of three Cymbopogon species (family Poaceae) were compared at three different levels of NaCl in water culture: 0 (control), 27 and 44 mM. The species differed considerably in their response to NaCl stress. In general, plant growth and essential oil content and yield decreased with an increase in water salinity in all the species. The decrease in oil yield was maximum in C. winterianus and least in C.flexuosus. Citral content increased under NaCl stress in C.flexuosus, while geraniol accumulation decreased in C. martinii. Maximum increase in sodium accumulation and decrease in K/Na ratio was observed in C. winterianus while sodium accumulation was least in C. martinii, particularly at 44 mM NaCl. C.flexuosus and C. martinii are suggested to be more tolerant of cultivation under saline stress than C. winterianus. Cymbopogon species accumulating less sodium and possessing high K/Na ratios under NaCl stress are suitable for adaptation for growth under saline conditions.

Physiological and metabolic responses of different genotypes of Cymbopogon martinii and C. winterianus to water stress

The effect of water stress on growth and essential oil metabolism wasstudied in two species of aromatic grasses under induced water stressconditions. Cultivars of Cymbopogon martinii andC. winterianus differed considerably in their response towater stress. Plant growth, oil yield and water potential decreased whileproline accumulation and oil biogenesis increased in the different genotypesunder water stress. Water stress induced a wide variation in essential oilcomposition, protein content and in activities of PEP carboxylase and nitratereductase in the different genotypes in terms of increase, decrease or nochange. The physiological and biochemical basis of drought tolerance inC. martinii has been elucidated on the basis of growth andmetabolic responses.

Cytokinins from marine organisms

Abstract Zeatin, zeatin riboside, dihydrozeatin and isopentenyladenine have been isolated from green algae and blue coral along with two new cytokinins, characterized as 2-hydroxy-6-methylaminopurine and 2-hydroxy-1′methylzeatin.

Relationship between gibberellin and cytokinin activity and flowering in Rosa damascena Mill.

Kinetin at 10 mg l−1 increased the number of flowers produced on Rosa damascena plants while GA3 inhibited flowering. In the leaves of non-flowering plants GA-like activity was high while specific cytokinin activity (fraction-II) was significantly higher in flowering plants. A novel compound 10- methyldihydrozeatin riboside and isopentenyl-adenine were identified from TLC fraction-II while TLC fraction-I yielded zeatin and 2-hydroxy-6-methylaminopurine.

The Effect of Kinetin on Flower and Oil Production in Rosa damascena

ABSTRACT In field trials over years on Rosa damascena Mill, foliar application of kinetin (20 mg/L) significantly increased number of flowers per plant, flower and oil yield. However, effect of kinetin on flower weight was not significant, while on oil content it was significant during 1991 but not in 1992. The effect of kinetin on flower and oil yield was more pronounced during “off season. Kinetin application also increased citronellol + geranyl acetate level in the oil by 13% and 24% over control by 20 mg/L concentration application in both the years respectively.