Growth‐induced water potentials and the growth of maize leaves
Profiles of water potential (Ψw) were measured from the soil through the plant to the tip of growing leaves of fully established maize (Zea mays L.). The profiles revealed gradients in transpiration‐induced Ψw extending upward along the transpiration path, and growth‐induced Ψw extending radially between the veins in the elongating region of the leaf base. Water moving upward required a small gradient while that moving radially required a much larger gradient primarily because the protoxylem vessels were encased in many small, undifferentiated cells that were likely to act as a barrier to radial flow. Upon maturation, these small cells enlarged and some began to conduct water, probably decreasing the barrier. In the mature leaf, the growth‐induced Ψw were absent but the transpiration‐induced Ψw remained. When leaves were growing, the growth‐induced Ψw moved water into the elongating cells during the day and night, and it shifted with changes in transpiration‐induced Ψw. The shift involved solutes accumulating in the growing region. When water was withheld, the growth‐induced Ψw disappeared and leaf elongation ceased even though turgor pressure was at its highest. Turgor was maintained by osmotic adjustment that doubled the osmotic potential of the elongating cells. If elongation resumed at night or with rewatering, the growth‐induced Ψw reappeared. If pressure was applied to the soil/root system to cause guttation and re‐establish the growth‐induced Ψw, elongation resumed immediately. These findings support the hypothesis that the primary control of growth is the disappearance and reappearance of the growth‐induced Ψw because the potential changed in the xylem and nearby cells, blocking or permitting radial water movement and thus blocking or permitting growth. [1]
Morphology and growth of maize
Maize is one of the most important food crops worldwide. It has a remarkable productive potential. However, considerable variation exists among varieties in morphology and growth habit. Management of a maize crop with respect to interaction of genotype and environment requires specific knowledge of maize growth and development. Maize (Zea mays L.) and all major cereal crops are members of the grass family, Gramineae. Worldwide, wheat, maize, and rice are produced in greater quantities than any other crop. Of these crops, maize has the highest average yield per hectare (Table 1). Although it occupies less land area than either wheat or nee, it is second only to wheat in total production. Maize has the basic structure of the grass family, having conspicuous nodes and internodes on the stem. The leaves grow in two opposite ranks; one leaf per node Maize is botanically unique among the cereal crops. It is monoecious (having separate male and female inflorescences on the same plant) and it produces grains on lateral rather than terminal branches. [2]
Relationships among Kernel Weight, Early Vigor, and Growth in Maize
Lack of early season vigor in maize (Zea mays L.) hybrids and inbreds from the USA limits their use in places with cool humid springs. Kernel size may be related to early growth of maize. Our objectives were to estimate general combining ability (GCA), specific combining ability (SCA), and reciprocal effects (RE) for early vigor and plant growth‐related traits and to determine the relationship between these effects and those of kernel weight. Ten maize inbreds were crossed in diallel fashion, including reciprocals in two different plots. Kernel weight was recorded for each seed source for each hybrid. The 90 hybrids were evaluated for 2 yr in a split‐plot design where genotypes were the main plots and seed sources were the subplots. Traits were early vigor, plant weight, pollen and silk date, leaves below the ear, total leaf number, and plant height. Significant GCA was detected for all traits except plant weight, and SCA was significant for all traits except kernel weight. Significant RE was detected for kernel weight, early vigor, and pollen and silk date. Inbred EP42 had the highest GCA and a favorable RE for early vigor. Regression on the RE of kernel weight was significant for the RE of early vigor (R2 = 0.67), plant weight {R2 = 0.36), and pollen (R2 = 0.52) and silk date (R2 = 0.45). The inbreds producing heavier kernels should be used as seed producing parents to obtain hybrids with better early vigor and earlier flowering dates. [3]
Exogenous Application of Glycinebetaine Facilitates Maize (Zea mays L.) Growth under Water Deficit Conditions
Aims: To determine whether the exogenous application of glycinebetaine (GB) can ameliorate the effects of water deficit on maize growth and physiological processes.
Study Design: Split plot design with water deficit being the main plot factor and GB application being the subplot factor. Treatment was a combination of water deficit level and GB application with 3 replications.
Place and Duration of Study: R.R. Foil Plant Science Research Center, Mississippi State University, Mississippi State, MS, USA between May and July 2010.
Methodology: A pot experiment was conducted using 31-d old ‘TV25R19’ maize irrigated with 750 ml pot-1 day-1 (WW: well-watered), 450 mL pot-1day-1 (WD60, 60% of WW) and 300 mL pot-1day-1 (WD40, 40% of WW) grown with or without GB application at each stress level. GB was applied as a foliar spray every 5 days at a rate of 4 kg ha-1. Soil moisture content and leaf water potential, growth, biomass, and gas exchange parameters were measured in response to the treatment variables.
Results: Significant GB and water deficit main effects were observed for plant height (PH), leaf dry weight (LDW), ear dry weight (EDW) and total dry weight (TDW) (P £ 0.05) while GB main effects alone were observed for node number (NN) and stem dry weight (SDW) (P £ 0.05). GB application increased leaf area (LA) (5,454 cm2 plant-1) in WD60 plants relative to untreated plants. No GB effect was seen under other treatment combinations at 10 or 20 days after treatment (DAT) measurements. GB did not increase stomatal conductance or transpiration at 10 or 20 DAT in plants subjected to water deficit. GB application resulted in leaf water potential values in the WD60 treatment that were statistically similar to the well-watered plants. Volumetric soil water content did not change with foliar GB application across water deficit treatments except under mild stress after 18 DAT, where soil moisture was higher for GB treated plants.
Conclusion: GB’s effect was most evident in plants from the WD60 treatment. GB application significantly improved PH, LA, LDW, SDW, EDW and TDW and did not influence NN under WD60 conditions. [4]
Effects of MAPKK Inhibitor PD98059 on Growth of Maize Seedling
Aims: Preliminary observations showed that 75 ìM PD98059 had a long-term effect on growth of maize seedlings. To verify and systemically analyze the effects of 75 ìM PD98059 on growth of maize seedlings, we designed and conducted this experiment.
Methodology: We recorded and analyzed the effects of 75 ìM PD98059 on growth of maize seedling during the first fourteen days. The growth traits were observed. The length, fresh weight, and dry weight of shoots or roots, and the root/shoot ratio of fourteen-day old seedlings were measured. Cutting analysis was conducted to analyze the effects of PD98059 on shoot growth.
Results: The shoot and root length of control showed about 1.38- and 1.5-fold longer than that of PD98059-treated seedlings, respectively. The shoot and root fresh weight of PD98059-treated seedlings declined to 80% and 79.4% of the control, respectively. The shoot and root dry weight of PD98059-treated seedlings declined to 68.3% and 69.8% of the control, respectively. PD98059 also decreased the length, fresh weight, and dry weight of cuttings.
Conclusion: PD98059 had a negative effect on the growth of maize seedlings and this effect was overall on both shoots and roots. The effect of PD98059 on shoot growth seemed to be not due to detrimental effects of PD98059 on roots. [5]
Reference
[1] Tang, A.C. and Boyer, J.S., 2002. Growth‐induced water potentials and the growth of maize leaves. Journal of Experimental Botany, 53(368), pp.489-503.
[2] G Kllng, J., 1991. Morphology and growth of maize.
[3] Revilla, P., Butrón, A., Malvar, R.A. and Ordás, R.A., 1999. Relationships among kernel weight, early vigor, and growth in maize. Crop Science, 39(3), pp.654-658.
[4] Raja Reddy, K., Brien Henry, W., Seepaul, R., Lokhande, S., Gajanayake, B. and Brand, D. (2012) “Exogenous Application of Glycinebetaine Facilitates Maize (Zea mays L.) Growth under Water Deficit Conditions”, Journal of Experimental Agriculture International, 3(1), pp. 1-13. Available at: https://www.journaljeai.com/index.php/JEAI/article/view/30409 (Accessed: 15January2021).
[5] Liu, Y. and He, C. (2013) “Effects of MAPKK Inhibitor PD98059 on Growth of Maize Seedling”, Annual Research & Review in Biology, 3(4), pp. 507-516. Available at: https://www.journalarrb.com/index.php/ARRB/article/view/24772 (Accessed: 15January2021).