Effect of the Duration of the Vegetative Phase on Shoot Growth, Development and Yield in Pearl Millet (Pennisetum americanum (L.) Leeke)

Craufurd, P. Q. and Bidinger, F. R. 1988. Effect of the durationof the vegetative phase on shoot growth, development and yieldin pearl millet (Pennisetum americanum (L.) Leeke).–J.exp. Bot. 38: 124–139 The duration of the vegetative phase (DVP) in millet, whichis the major cause of variation in the crop duration, has markedeffects on the number of productive tillers per plant and onmainshoot (MS) and tiller grain yield. Daylength extensionswere used to vary the DVP and the effect on factors affectingpanicle (tiller) number per plant and panicle yield examinedin millet hybrid 841A x J104, grown in the field at Hyderabad,India. Tiller appearance, shoot leaf appearance and leaf area,and stem and panicle growth, in both MS and primary tillers(PTs), were monitored at frequent intervals over the season.At maturity grain yield per shoot was measured The concept of thermal time was used to describe shoot development.The rates of tiller appearance and shoot leaf appearance werelinearly related to thermal time and were not affected by DVPtreatments. The duration of the growth phase from panicle initiationto flowering (GS2) and from flowering to maturity (GS3) was320 and 390 degree days (°Cd), respectively. There was nodifference in rates of leaf or tiller appearance or developmentbetween MS and PTs. Tiller appearance, tiller leaf appearanceand tiller apical development all ceased at the same time inthe later initiated PTs, approximately 550 °Cd from sowing,shortly after rapid stem growth had begun. Tillers that didnot survive were all vegetative or in the early stages of reproductivedevelopment at this time The rate of accumulation of dry matter per plant was similarin all DVP treatments, but in the longer DVP treatments a greaterproportion of the dry matter was partitioned to the MS. Mainshootstem and panicle growth rates were increased by a longer DVP,as was grain yield on the MS, and these were related to increasedMS leaf area. Concurrently, growth rates and yields in laterinitiated tillers were reduced in relation to their leaf areas.Stem growth rate was proportionately increased more than paniclegrowth rate in the longer DVP treatments and this, combinedwith a longer duration of stem growth, resulted in greater stemdry matter at maturity and, therefore, in reduced harvest index.     

The Effect of Flowering on Stomatal Response to Water Stress in Pearl Millet (Pennisetum americanum [L.] Leeke)

Stomata on upper leaves of drought-stressed pearl millet (Pennisetumamericanum [L.] Leeke) crops were more open in flowering (F)than in pre-flowering (PF) plants. This was not due to differencesin leaf water potential (). Stomata of PF plants closed when fell to about –1.7 MPa, while on F plants stomata closedonly when approached –2.3 MPa. Osmotic adjustment did not account for these differences asrelations between turgor potential (_P) and were similar inF and PF plants. While stomata of PF plants closed as W becamezero, in F plants stomata remained open even after bulk leafturgor was lost. Differences between F and PF plants were not explained by differencesin age of leaves sampled. However, leaves of water-stressedPF plants had higher levels of abscisic acid (ABA) than leavesof F plants, despite similarities in water status. From theseresults and from relationships between g_L and stage of panicledevelopment, it is concluded that the tendency of stomata toremain open despite water stress and loss of bulk leaf _P isrelated to the presence of an emerged panicle. Hypotheses whichaccount for this effect are discussed. Key words: Pennisetum americanum [L.] Leeke, Pearl millet, Flowering, Stomata, Water stress, Abscisic acid     

Solute Accumulation and Growth in Plants of Pearl Millet (Pennisetum americanum [L.] Leeke) Exposed to Abscisic Acid or Water Stress

Henson, I. E. 1985. Solute accumulation and growth in plantsof pearl millet (Pennisetum americanum [L.] Leeke) exposed toabscisic acid or water stress.—J. exp. Bot. 36: 1889–1899.Experiments were conducted to investigate whether abscisic acid(ABA) elicits the accumulation of solutes and lowering of osmotic(solute) potential (₂) which occurs in leaves of pearl millet(Pennisetum americanum [L.] Leeke) exposed to water stress.When (?)–ABA was injected into the base of the shoot of15–d–old plants, ₂ of the fifth leaf was reducedsignificantly below controls 27–72 h after treatment.The reductions, however, were small (< 0.10 MPa) and wereaccompanied by a significant inhibition of shoot growth. Incontrast, no significant reduction in ₂ or in growth occurredwhen the hormone was introduced directly into leaf five viaits mid–rib. ABA concentrations in leaf five were highshortly after direct injection, but declined to control levelswithin 48 h. Injecting ABA into the shoot base resulted in lowerleaf five ABA concentrations. Hence, the ABA concentration inthe leaf was not the most critical factor for its effect on₂. ABA also reduced ₂ of shoots when applied to seedlings 48h or 72 h after sowing via the roots. As with older plants,the effects of ABA on ₂ were small ( 0–2 MPa) and wereaccompanied by inhibition of shoot growth. A water stress treatmentand an ABA treatment were compared. Although both treatmentsresulted in a similar degree of growth inhibition, the stresstreatment was much more effective than was ABA in reducing ₂. Key words: Pennisetum americanum [L.], pearl millet, abscisic acid, water stress, osmotic     

Uptake,Translocation, Distribution and Persistence of 14C-Metalaxyl in Pearl Millet (Pennisetum americanum) [L.] Leeke)1

Time course absorption and desorption of metalaxyl by seeds of pearl millet was analysed by following chemical kinetics equations. Uptake of metalaxyl through roots, leaves and seed, its translocation and distribution in different plant parts and persistence following seed application were studied in pearl millet using ¹⁴C-metalaxyl. Both uptake and efflux of metalaxyl by pearl millet seeds were complex and compartmentalized. Distribution inside the seed was not uniform. A major part of applied fungicide remained within the treated plant part, particularly after seed and foliar applications. Metalaxyl was ambimobile inside the plant and was found to get accumulated at apex and margins of leaf blade. No metalaxyl could be detected in grains, harvested from plants grown from metalaxyl treated seeds.     

Effect of Temperature During Various Growth Stages on Grain Development and Yield of Pennisetum americanum

In controlled temperature glasshouses plant morphology, gramdevelopment and yield of pearl millet (Pennisetum americanum)were markedly affected by temperature during three stages ofplant growth: vegetative, stem elongation, and grain development.High temperature (to 33/28 °C day/night) during all threegrowth stages lowered grain yields by reducing basal tillering,numbers of grains per inflorescence, and single grain weight.Low temperature (21/16 °C) during the vegetative stage increasedbasal tillering and, as a result, total grain yield per plant.However, low temperature during the stem elongation stage reducedspikelet fertility and influorescence length, and thereby reducedthe potential main shoot grain yield. Low temperature duringgrain development increased the grain filling period and grainyield. The rate of grain filling did not vary over the rangeof 21/16 to 33/28 °C. Although plant morphology and grainyield were markedly affected by pre-anthesis thermal environment,grain development was not. At all temperatures ethanol-solublecarbohydrates stored in the stem were depleted during earlygrain development.     

Dependence of Abscisic Acid Accumulation in Leaves of Pearl Millet (Pennisetum americanum[L.] Leeke) on Rate of Development of Water Stress

Henson, I. E. 1985. Dependence of abscisic acid accumulationin leaves of pearl millet {Pennisetum americanum [L.] Leeke)on rate of development of water stress.—J. exp. Bot. 36:1232-1239. The amount of abscisic acid (ABA) which accumulated in attachedleaves of pearl millet (Pennisetum americanum [L.] Leeke) inresponse to water stress was found to depend on the rate atwhich the stress developed, as well as on the intensity of stress.In young, pot-grown plants, the increase in leaf ABA concentration([ABA]) was linearly related to the fall in water () and turgor(_p) potentials. However, the amount by which [ABA] increasedper unit change in or _p, was greater at high than at low ratesof stress development. Evidence is presented which suggeststhat the same effect may occur under field conditions and contributeto differences in ABA accumulation between plants grown in potsand those grown in the Held. Key words: Pennisetum americanum, abscisic acid, water stress, rate of stress development