As predictable, negative effects occurred for maize crop when grown in alkaline condition as compared to non- alkaline soil. The short stature of maize plant is associated with break in supply of nutrient and water for normal metabolic process on account of perturbation in stomatal functioning and root architecture . The reduction in the growth of rapeseed cultivars grown in salt-stress conditions was associated with a reduction in the RWC and an increase in electrolyte leakage . In the present study, it was observed reduction in RWC and increased EL in alkaline stress soil. There was negative correlation between electrolyte leakage with plant height (r= -0.897**). Decrease in plant height due to alkaline stress as perceived in the present study was in agreement with earlier workers . Silicon interventions as soil application added to alkaline stress soil overcame the negative effect and it resulted in increase in plant height with silicon levels and maximum effect was noticed with 150 kg Si/ha. The positive effect of silicon could be due to increased cell division, cell elongation and also deposition of silicon in plant tissue causing erectness of leaf and stem.  observed increase in plant height of wheat with silicon under drought stress.
The reduced dry weight of maize with alkali stress levels is associated with water stress, ion toxicity, nutritional disorder, oxidation stress, membrane disorganization, reduction in cell division and expansion [42 & 47]. Decrease in plant biomass due to salt stress was reported . This was confirmed by significant negative correlation between electrolyte leakage with dry weight (r = 0.830**). Addition of silicon to soil experiencing alkaline stress improved shoot dry weight. Improved relative water content, reduced electrolyte leakage, improved anti-oxidant systems on addition of silicon was noticed in the present study which would have increased shoot dry weight. Significant improvement in shoot dry weight of maize by silicon in salt stress was reported earlier by several workers .
Relative water content (RWC) in leaves is known as an alternative measure of plant water status reflecting the metabolic activity in tissues. The curtailment in relative water content under alkaline stress is mainly attributed to osmotic stress that is posed by high pH environment. This in turn generate accumulation of proline which causes water deficit condition, and as a consequence slows down water uptake. Strong linear regressive model of the increasing alkaline concentration (independently variable) and the decrease of RWC in leaf (r2 = 0.9766) as dependent variable was noticed in the present study (Fig. 5). Exogenous silicon application triggered RWC recovery in alkaline stresses plant.  found that silicon promoted root growth and root hydraulic conductance thereby increasing root water uptake and further improving leaf water content by regulating the activity of aquaporins under salt stress. Improved RWC might be because of the deposition of silicon as silicate crystals in epidermis tissues as this constitutes an obstacle to water transpiration through stomata and cuticle helping to reduce alkalinity . The present outcome was corroborated by earlier researchers . This was confirmed by a strong linear relationship between silicon levels with RWC (r2 = 0.9895**) (Fig. 5)
Electrolyte leakage is widely used as a test for the stress-induced injury of plant tissues and a measure of plant stress tolerance. Alkali stress at various concentration increased electrolyte leakage in maize leaf compared to non-stressed soil. It is mainly caused by the efflux of K+ and so-called counter ions (Cl−, HPO42−, NO3−, citrate3−, malate2−) that move to balance the efflux of positively charged potassium ions . Strong linear regressive model of the increasing alkaline concentration (independently variable) and the increase of EL in leaf (r2 = 0.9546) as dependent variable was noticed in the present study (Fig. 5). Application of silicon reduced electrolyte leakage .This may be explained by the fact that Si has the ability to maintain cells by improving the permeability of their plasma membranes, which improves access into the cell by antioxidative enzymes . This was supported by significant positive linear relationship observed between silicon levels and EL (r2 = 0.9926**) (Fig. 5)
Amidst all stresses adaptation, osmotic adjustment is a part of salt stress forbearance mechanism to offset the loss of turgor by increasing and maintaining higher amount of intercellular compatible solutes in the cystol and vacuole . Proline is one of the key osmolytes contributing to osmotic adjustment. Maize plant recorded a higher proline concentration when it was grown in alkali stress soil. In durum wheat seedlings proline can contribute for more than 39% of the osmotic adjustment in the cytoplasmic compartments of old leaves . Production of proline in plant under stress environment is either associated with protein biosynthesis genes (P5CS, P5CR) or repression of the genes of its degradation pathway (PDH silencing) . Addition of silicon reduced proline content in maize leaf grown in alkali stress soil. Si may provide a protective role helping to prevent lipid peroxidation induced by NaCl, because of this, proline content was significantly lower in the Si-treated maize seedlings under salt stress than those under salt stress without Si treatment .  confirmed the present findings that addition of silica reduced the proline content and increases protein content in soybean to counter balance the salt stress.
Polyphenol cmpounds lend a hand in plant protection against ROS and it is produced in large quantity, whenever aerobic respiration or photosynthetic metabolism are disabled by environment stress . The increase in phenolic contents in different plant tissues under increasing salinity has also been reported in a number of plants . The present work also reports the increase in phenol content in maize plant grown in alkali stress soil. Silicon application improved phenol content in maize leaf grown in alkali stress.  reported 36% increase in phenol due to silicon in barley.
Maize leaf recorded more soluble protein grown in alkali stress compared to non –stressed soil Plant experiencing stress normally pile up small molecules mass protein which is used as storage nitrogen that could be mobilized after stress relief . Additionally, these proteins could also have a role in osmotic adjustment .  reported increase in soluble protein in maize genotypes grown in salt stress soil. The exogenous application of silicon improved soluble protein because silicon has pivotal role in binding amino acids to form specific proteins . Silicon is actively engaged in the formation of DNA and functioning of mRNA .  reported application of potassium silicate improved soluble protein. Furthermore, through the regression test, it showed that alkaline levels and silicon doses determined significantly the levels of proline (r2 = 0.9791**, 1**), phenol (r2 = 0.9502**, 0.9897**) and protein (r2 = 0.9883**, 0.9983**), respectively (Fig. 6)
Antioxidant protective enzymes exist in higher plants under different growth conditions. In plants antioxidant enzymes mainly include catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD) and its activity triggered by the increase in the production of ROS or the measured activity might be protective mechanism adopted by maize against oxidative damage  SOD, POD and CAT activities in maize leaves increased linearly with concomitant increase in alkali stress level. SOD is the probably the key enzyme to defend against toxic ROS . POD catalysed the reaction between H2O2 and ROOH to H2O and ROH ameliorated cell damage which can inhibit the Calvin Cycle . Catalase is a principal enzyme that scavenges active oxygen species and prevents lipid peroxidation, cell membrane damage and chlorophyll degradation. CAT controls H2O2 level in plant cells and participates in the photosynthetic process. The significant positive correlation between the SOD and POD (r = 0.8736**), SOD and CAT (r = 0.8908**) and CAT and POD (r = 0.9446**) observed in this study suggested a synergistic effect of POD, CAT and SOD in resistance to alkali stress. This is similar to , who reported that the defence capability of antioxidant enzymes depended on cooperative actions of enzymes. Silicon interventions through soil application improved SOD, POD and CAT enzymes activities in maize leaf grown in alkali stress soil.  reported that Si application strengthens the antioxidant defence system and maintains normal physiological processes.  explained that Si enhanced the activity of antioxidative enzymes and reduced plasma membrane permeability.  observed that addition of silicon improved antioxidant enzymes in wheat seedling grown in salt stress.