Extreme Temperature Responses, Oxidative Stress and Antioxidant Defense in Plants - Abiotic Stress: Plant Responses and Applications in Agriculture - page 180

during chilling stress. Without these in extreme cases, chilling results in accelerated senescence
and eventually plant death [114].

3.3. Reproductive development

Reproductive phases of the life cycle of plants are more vulnerable to cold stress [115]. The
reproductive phase faced to LT stress is influenced diversely in its different sub-phases. During
the development of male gametophyte LT causes disruption of meiosis, tapetal hypertrophy,
stunted development of pollen grain, anther protein degradation, pollen sterility, pollen tube
deformation. In female gametophyte development its effects are characterized by reduced style
and ovary length, disruption of meiosis, reduced stigma receptivity, callose deposition in style,
damage to embryo sac components, and arrest of the fertilization process. At flowering LT
may cause delayed flowering, bud abscission, sterile or distorted flowers, while at grain filling
the source-sink relation is altered, kernel filling rate is reduced and ultimately small sized,
unfilled or aborted seeds are produced [109, 116]. Flower buds of Simmondsia chinensis can be
damaged or killed by temperatures of −2° to −5.5°C [117]. Farrell et al. [118] observed that cold
water significantly reduced panicle emergence in rice. Low temperatures affect not only
normal heading but also panicle exsertion and prevent the normal elongation of internodes of
rice. Cold stress (11°C) caused abnormality in panicle initiation process, delayed heading,
incomplete panicle emergence, sterile and malformed spikelet and spikelet degeneration
symptom in rice genotypes [98, 99b; Fig. 2, 3]. In canola low, but nonfreezing temperatures
prior to flowering slow the rate of plant development, delayed flowering, slower the rate of
flower opening and reduces the amount of pollen shed and in severe frost the pod abortion is
evident in many species [119]. The effect of LT prevailing at the early stages of plant growth
is sometimes associated with the premature flowering in Chinese cabbage [120].

A B

Figure 2. Spikelet degeneration (A) and incomplete of panicle exsertion (B) of rice due to cold stress