**4. Influence of abiotic stresses on seed production and quality**

Abiotic stresses exert negative influence on production of seed primarily by hampering germination as well as photosynthetic efficiency and translocation of assimilates from source (leaf) to sink (seed). Further, flowering, fertilization and seed filling phases are greatly affected under abiotic stresses. Reduced activity of acid invertase restricts reproductive parts of plant through phloem unloading. Reduced endosperm size, abortion of embryo, less seed filling, unfilled seed etc. drastically reduce the seed production and quality. Deterioration of yield and quality arises also from deficiency of supply of essential inputs to the plant under abiotic stress. The influence on seed formation and quality is resulted from complex relationship between individual stresses. For instances, changes in gene expression, oxidative damage, alteration of ion distribution and cell homeostasis lead to loss of production and quality of crop under abiotic stresses. Reduced productions of various crops under abiotic stresses have been listed in **Table 1**. The specific influence of different abiotic stresses on seed production and quality are briefly discussed here under.

#### **4.1 Water stress**

Drought is the principal limiting factor of growth, yield and quality of cereal crops throughout the world. Drought (water deficit) affects the plant at all the stages by altering its physiological, biochemical, molecular properties. Degree of yield loss depends


#### **Table 1.**

*Major crops under harmful impact of abiotic stresses on production.*

on occurrence and severity of drought. However, drought stress at flowering as well as post flowering grain filling period is extremely detrimental which reduces the seed yield most. Drought reduces production of flowers, pollen viability, fertilization and seed filling, resulting in loss of production qualitatively and quantitatively. Shortening of

#### *DOI: http://dx.doi.org/10.5772/intechopen.106045 Influence of Abiotic Stresses on Seed Production and Quality*

pollination and seed filling periods and early maturity lead to less or immature production of seeds. Abortion of reproductive parts of plant is a common phenomenon under drought stress at reproductive stage. Further, under drought stress, increment of toxic ion concentrations in cell, loss of cell turgidity through disruption of water streaming etc. reduce leaf growth leading to poor photosynthesis as well as translocation of dry matter from source to seed (sink). In legume crops, drought stress reduces nodulation, nitrogen fixation and thereby, hampers seed production. Few research works [7] revealed that mild drought stress during seed filling stage leads to increase in protein content of plant. For instance, [48] reported loss of gluten, glutenin, gliadin etc. but increase of protein in wheat under drought stress. However, severe water deficit leads to reduction in amino acid pool and its incorporation to protein as well as less accumulation of N, P, Fe, and Zn, which in turn decreases the protein content of the seed. It has been also observed from many research work that protein content increases after withdrawal of drought in seed filling stage [49]. Oil, oleic acid, glucose, sucrose, fructose etc. decrease with increase of drought during seed filling stage. PUFA contents of sunflower [50] and groundnut [49] are found to decrease under drought stress. β-glucan content of seed also decreases under drought stress. Increased sucrose content and less formation of starch in potato are observed under drought stress [51]. Reduction of starch synthetase activity under drought stress leads to amylose content of wheat [52]. Further, drought stress reduces uptake of nutrients and thereby, lowers the nutritional quality of seed. Increase of electrical conductivity, poor germination and vigor can be seen from the seeds produced under drought stress.

Excessive water use can lead to deficiency of oxygen and accumulation of toxic chemicals inside the plants and thus, hampers number of spike/pod per plant, number of seeds per spike or pod, seed weight leading to reduction of seed production. Further, restriction in uptake of nutrients specially, N under high water content due to leaching and/or dentrification losses can result in quality deterioration of the produce, specially, protein.

#### **4.2 Salinity stress**

Salinity is especially harmful at seedling, flowering and reproductive stages. It plays detrimental role in inhibiting seed germination or causing seedling mortality and less plant population which ultimately affects the seed yield. Further, production of seeds are greatly affected under salinity stress due to reductions in photosynthesis, transpiration, stomatal conductance and metabolic activities owing from less chlorophyll, carotenoid, relative water content (RWC) and increased ion toxicity. Nodulation and nitrogen fixation in leguminous crops are also affected by excess salt content. Poor pollen viability and restricted translocation of assimilates to seed lead to low seed production. Restricted supply of nutrient and water to the plant from soil results in detrimental influence on seed production and quality of crops. Oil, protein and starch contents decrease due to disturbances in nitrate uptake and nitrogen metabolism under high salinity. PUFA content of sunflower decreases under drought stress [53].

#### **4.3 Temperature stress**

Temperature stress (high/low) greatly affects the seed production and quality of the produce. Loss of yield is resulted from poor seed germination and plant stand establishment. Further, high temperature during flowering and grain filling period can lead to pollen desiccation or sterility, fertilization failure, dysfunctioning of

tapetal cells, loss of cell turgor, less leaf area (and increased senescence rate), reductions of chlorophyll, CO2 assimilation or photosynthesis and increment of photorespiration [54]. Reduction of net photosynthesis due to poor rubisco activity and decrease in translocation of assimilates hamper the production of seed. It has been also noticed that heat stress reduces seed filling duration resulting in loss of production as well as its quality [55]. Increment of soil temperature hampers root growth and increase respiration rate, which further restrict uptake of nutrients and water from soil resulting in not only loss of yield but also changes in quality of the produce. Heat stress, specifically, restricts starch and protein synthesis, which are major determinants of seed quality. For instances, during seed filling period, increase of temperature leads to imbalance supply of nitrogen in pulses [56]. Starch and protein contents also decline under heat stress in wheat and maize [57, 58]. However, it has been also noticed that heat stress has positively affected on seed protein content. For instances, elevated soil temperature (around 2.5°C) has significantly improved protein content (aspartate, glycine, alanine, arginine, valine and tryptophan) of barley [59]. Lin et al. [60] observed that increased temperature during early seed filling period improved protein content in rice but reduced prolamins. In leguminous crops, heat stress mostly reduces protein contents and increases oil contents due to antagonistic effect between oil and protein [61]. Heat stress during flowering and seed filling stages reduces the starch synthesis period resulting in less accumulation of starch (poor conversion from sugar to starch). However, [62] reported increased starch content in potato under heat stress. Under heat stress, PUFA content of soybean declines [63]. Vitamin C, minerals etc. are also low in seed under heat stress.

Cold stress causes stunting in plant growth, vascular browning and abnormal seed ripening. Low temperature during the flowering and seed formation phases results in pollen sterility, limiting pollen grain germination. Cold period in flowering is the most sensitive period in plants like rice. Cold stress shortens the seed filling stage and can lead to energy deficiency and thereby, sterility of gametophytes by hampering carbohydrate metabolisms. It causes cell dehydration and crystallization of water in cell. Further, there is production of ROS under low temperature (oxidative stress). Infestations of soil-borne diseases to seedling stage of the crop are also visible under cold stress. As a consequence, yield attributes and production of seeds are greatly hampered. Accumulation of minerals, amino acids, protein, starch, fat and crude fibers decreases and sugar concentration increases in seed under cold stress [31].
